LEADING ARTICLE
Sports Medicine 14 (6): 366-375, 1992 0112-1642/92/0012-0366/$05.00/0 © Adis International Limited. All rights reserved . SP01186
Information Processing and Accidental Injuries Sima Taimela Helsinki Research Institute for Sports and Exercise Medicine, Helsinki, Finland
The prevention of sports injuries is an important objective in the reduction of accidental injuries (de Loes & Goldie 1988; Lattila et al. 1982; Lindqvist 1989; Sandelin et al. 1987). Sports accidents are costly for society and the injured individual (de Loes 1990). Four areas can be identified in the sports injury prevention (Backx et al. 1991; Van Mechelen et al. 1987). The first area includes the analysis of the nature, extent and severity of sports injuries. Secondly, the aetiological factors involved in sports injuries are identified. Thirdly, the application of preventive measures is done , followed by analysis of the effects ofthe preventive measures. However, very few studies have looked at aetiological factors and preventative measures (Ekstrand & Gillquist 1983a; Torg et al. 1985). Several aetiological factors involved in sports injuries have been analysed (Backx et al. 1991; Lysens et al. 1989; Taimela et al. 1990a). Commonly, injury risk factors in sports are classified as activity related (extrinsic factors) and participant related (intrinsic factors). Each type of activity has its characteristic injury profile and degree of risk and the type of injuries varies widely (de Loes & Goldie 1988; Kujala et al. 1988). Extrinsic injury risk factors include, for example, training errors (Clement et al. 1981; McKenzie et al. 1985; Sedgwick et al. 1988) and environmental conditions, such as terrain, weather and equipment (Ekstrand & Gillquist 1983b; Ekstrand et al. 1983; Grace et al. 1988; Hulkko 1988; James et aI. 1978; McKenzie et al. 1985). The participant re-
lated injury risk factors include abnormal anatomy or biomechanics (Kujala 1986; Lysens et al. 1989), poor aerobic or muscle conditioning (Kerr & Minden 1988; Watson 1984),former injuries (Ekstrand & Gillquist 1983b; Lysens et al. 1984; Robey et al. 1971), psychological factors (Jackson et al. 1978; Taerk 1977; Valliant 1981) and accumulation of life stress (Bramwell et al. 1975; Coddington & Troxell 1980; Cryan & Alles 1983; Kerr & Minden 1988; Passer & Seese 1983). There are few studies concerning the relationship between central motor control and sports injuries even though it is presumable that low grade motor control predisposes to accidental injury. It has also been suggested in some papers that poor coordination and slow psychomotor speed predispose to injury (Beck & Day 1985; Beck & Wildermuth 1985; Edwards 1988; Inkelis et al. 1988; Kelley 1990) and some experimental evidence has been recently gained also with regard to the hypothesis. This review discusses findings on information processing and the musculoskeletal injuries to-date and offers suggestions for future study. The concept of central motor control is presented in detail as it represents an essential part of information processing requirements in sports.
1. Information Processing Variables and Injuries: Existing Literature Low grade intelligence quotient (IQ) and slow choice reaction time were related to history of accidental bone fracture in young men (Taimela 1990;
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Taimela et al. 1991a). The study group included a sample of 123 army conscripts who were interviewed for previous accidents and tested for IQ and reaction time . Eight bone fractures were recorded during the previous 20 months in the subjects. The fracture group gained poorer results both in all the components of IQ tested and in slow choice reaction time. Because of the small number of injuries, the study was repeated in a sample of 823 army conscripts using the same tests. Again, low grade arithmetic ability and slow reaction time were related to accident history (Taimela 1992). Low grade army intelligence test result was predictive of motor vehicle accident mortality in the Australian troops during the Vietnam war (O'Toole 1990). Individuals with back pain (Bergenudd & Nilsson 1988), knee pain (Bergenudd et al. 1989), and shoulder pain (Bergenudd et al. 1988) in middle age had been less successful in a childhood intelligence test than individuals with no musculoskeletal complaints. Unfortunately, single accidents were not considered in the study group. Subjects with chronic low back pain were slower in a reaction time test than controls in a preliminary study (Taimela et al. 1992). However, long reaction time may be a consequence of back pain instead of the cause. Simple reaction time was associated with injuries in soccer (Taimela et al. 1990b). Unfortunately, neither choice reaction time nor IQ was tested in this study. Generally, an association between reaction time and IQ variables and injuries has repeatedly been found. However, most studies have shown an association between information processing variables and less severe injuries only. Further studies are needed on the association between information processing variables and severe injuries .
Stimulus
. ~
Stimulus identification
2. Central Motor Control: The Concept of Information Processing Humans are considered as processors of information (Marteniuk 1976; Schmidt 1988; Smith 1980). In this concept , information from the environment is obtained by specific sense organs and processed. Commonly, the processing is considered to include stimulus identification, response selection and response programming (fig. I) [Marteniuk 1976; Matthews & Dom 1989; Schmidt 1988; Smith 1980]. Accordingly, human movements may be considered as responses to the environmental stimuli . However, the simple signal-response model is sufficient to explain only the most simple movements; it is incompetent in interpreting complex continuous or serial movements, or multiple simultaneous tasks.. More sophisticated models of human motor functioning have accordingly been presented . A 2-stage model of information processing includes at the lower level stimulus processing, feature extraction, response choice and motor adjustment (Matthews & Dom 1989; Sanders 1983). The higher level of control includes, for example, memory load, arousal , conscious att ention and resource distribution (fig. 2) [Matthews & Dom 1989; Sanders 1983; Schmidt 1988]. These response models, however, must be considered as simplifications of complex human motor behaviour. Three different techniques may be described in the measurement of motor responses: speed, accuracy, and magnitude of the movements (Schmidt 1988). Perhaps the most common approach is to consider the duration of the various information processes. . Fundamental to the measurement of speed is the assumption that the person who can
Response selection
Fig. 1. A simplified information processing model (after Schmidt 1988).
Response programming
Response
.
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execute more repetitions in a limited amount of time, or who can produce the specified behaviour in less time, is the more skilful. 2.1 Speed of Information Processing Psychomotor speed of reaction, i.e. the time from the onset of an unexpected stimulus to the initiation of the response, has been recognised as a means of relating mental events to physical measures since the nineteenth century. Reaction time measures are common in research for 2 primary reasons. First, reaction time measures are components of real life tasks, especially in sports and in traffic. Secondly, reaction times measure the time taken for mental events, such as stimulus processing, decision making and response programming (Marteniuk 1976; Matthews & Dorn 1989; Schmidt 1988; Smith 1980). Conventional methods in the assessment of reaction times have been apparatus tests involving motor response to visual stimuli (fig. 3). Simple reaction time, in which there is only I signal and corresponding response, is usually distinguished from choice reaction time. In reaction time, there are several signals and corresponding responses. Reaction times are also often differentiated into decision and movement time. Decision time is the interval between the arrival of the signal and the beginning of response to it, and movement time, the interval from the initia-
Attention
tion of the response to the completion of the movement (fig. 4). 2.1.1 Testing of Reaction Times Several factors associated with the equipment and testing facilities have an effect on reaction time test results. These determinants include (I) sensory factors, such as intensity of the stimulus; (2) response characteristics, such as size and distance of the target; (3) preparation, i.e. possible warning signal before the stimulus and length of the foreperiod; and (4) complexity of the choice (Brebner & Welford 1980; Rabbitt & Banerji 1989; Schmidt 1988; Welford I980a). Choice reaction time is linearly related to the log of the number of stimulus alternatives, the relation being known as Hick's law (Hick 1952; Schmidt 1988; Welford I980a). The amount of practice before the trial is a major contributor in the reaction time test results also (Rabbitt & Banerji 1989; Welford I980a). The dominance of visual sense has been noticed in several studies (Dickinson 1968; Jordan 1972; Kamen & Morris 1988;Klein & Posner 1974). Reaction times vary across the sensory modalities while, for example, auditive and proprioceptive reaction times are shorter than visual reaction times and vestibular stimuli produce long reaction times (Brebner & Welford 1980; Kamen & Morris 1988). These variations may rise from differences in peripheral sensory mechanisms rather than from the central processing of the information (Brebner & Welford
Arousal
Memory load
Resources
Resource allocation ~r
Stimulus ...
...
Stimulus identification
~Ir
Feature extraction
Response selection
Response programm ing
Response
.....
Fig. 2. A 2-stage information processing model (after Marteniuk 1976; Matthews & Dorn 1989; Schmidt 1988; Smith 1980).
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• K2
o
K3
L3
L2
•
o
Attention light
•
0
L1
Kt
o
Standby button
L4
0
• K4
Fig. 3. Choice reaction time apparatus: a schematic presentation. Ll, L2, etc. = stimulus light I, 2, etc.; Kl, K2, etc. = corresponding key. A finger is held ready on the standby button in the beginning of the test. When the attention light is turned on the subject focuses his/her attention. When the stimulus light is turned on, the subject releases the standb y button and presses the button corresponding to the stimulus as fast as possible. The speed of decision is measured as the interval between the appearance of the stimulus and release of the standby button . The speed of movement is measured by the interval between releasing the standby button and pressing the button corresponding to the stimulus. Mean decision and movement times are calculated from several recorded attempts. The total choice reaction time (CRT) is calculated as an arithmetic sum of the decision and movement times.
1980). For example, there are differences in afferent conduction times . Currently, however, no definite evidence can be shown to demonstrate that the central decision component of reaction time is similar in all the sensory modalities. It has also been suggested that the nature of the stimulus which initiates the response may affect central processing requirements to initiate the response (Kamen & Morris 1988). 2.1.2 Subject-Related Factors Affecting Reaction Times Subject-related factors that may affect reaction time include age and gender. Men are faster than women in both reaction and movement, and speed of both functions increases up to early adulthood and then decreases in all the levels of test complexity (Chodzko-Zajko & Ringel 1987; Era et al. 1986; Hodgkins 1963; Stelmach et al. 1987; Welford 1980b). The contribution of age in the reac-
tion time test results in the age group 17 to 30 years is minimal (Taimela 1991b). Many studies have shown a relation between slow reaction time variables and low grade IQ (Buckhalt et al. 1990; Era et al. 1986; Geary & Widaman 1987; Jensen & Munro 1979; Jensen & Vernon 1986; Lindley et al. 1988;Matthews & Dorn 1989;Neubauer 1990). The relation between IQ and reaction time is consistent in both decision time and in movement time regardless of task complexity (Buckhalt et al. 1990; Neubauer 1990). Educational , occupational or lifestyle factors and smoking may have some influence on reaction times. The results of occupational and educational factors in reaction times have been disputed (Heckel et al. 1989; Kilburn et al. 1989; Slack et al. 1988). Systematic physical activity and short reaction times are related in older age groups only (Baylor & Spirduso 1988; Chodzko-Zajko & Ringel 1987; Clarkson-Smith & Hartley 1989; Forth & Salmoni 1988). Prolonged tobacco deprivation
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RT
Warning
MT
DT
Foreperiod
Stimulus
t
Start of response
Endof response
f
Fig. 4. Components of reaction time (RT = reaction time; DT = decision time; MT = movement time).
lengthens reaction times in smokers, but no difference has been found between smokers and nonsmokers in reaction times (Beh 1989; Hill 1989; Hughes et al. 1989; Snyder & Henningfield 1989). Some studies have reported differences in reaction times between athletes and nonathletes or between different levels of activity within athletes (Christenson & Winkelstein 1988; Harbin et al. 1989; Mero et al. 1989; Taimela et al. 1990b). It is still not known if speed of reaction improves in physical activities or if athletes are chosen into different activity levels because of variations in psychomotor speed.
have been widely used. These tests make objective testing of intellectual performance possible (Buros 1978; Cronbach 1970; Guilford 1971; Wechsler 1958). Some examples of widely used tests are Cattells' Culture Fair Intelligence Test (1960), Raven's Advanced Progressive Matrices (1965) and AH2 and AH3 tests of general reasoning (Heim et al. 1974). The tests are measures of traditional intelligence or convergent thinking in contrast to tests of creativity (Child 1970; Guilford 1971; Persaud & Salmon 1988). The IQ tests commonly include subtests for at least spatial, verbal and arithmetic ability and a total score.
2.2 The Concept of Intelligence Many psychometric intelligence quotient (lQ) tests that utilise paper and pencil have been developed during the last few decades (Buros 1978). Most tests are descendants of the Wechsler Adult Intelligence Scale (WAIS) [Wechsler 1958], thus, originally descendants of Binet's intelligence scale from the nineteenth century. As there is no general agreement concerning IQ testing, different components of intelligence have been analysed. Verbal and arithmetic ability and performance in image tests are the conventional tests. Factor speed plays an important role in the IQ tests, that is, the tests reflecting both speed of recognition of structures and speed of performance. Information, comprehension, arithmetics, similarities, vocabulary, block design, picture completion, picture arrangement, object assembly and coding are some subtests that
2.3 The Relationship Between Reaction Time and IQ A few hypothetical questions concerning the IQreaction time relationship are uncertain. It is not known if these processes are associated with some global characteristic of the mind or with some specific processing modules. The 2-stage model of reaction time includes at the lower level stimulus processing, feature extraction, response choice and motor adjustment (fig. 2). The higher level of control includes memory load, conscious attention and resource distribution (Matthews & Dorn 1989; Sanders 1983). The participation of the different levels of control in IQ and complex reaction time remains unresolved. Many studies have shown essentially zero correlations between reaction time and movement time (Henry 1961; Schmidt 1988),
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suggesting that they are based on separate abilities. However, higher correlations between movement time and IQ have been reported than between decision time and IQ independent of task complexity (Buckhalt et al. 1990; Neubauer 1990; Widaman & Carlson 1989). A satisfactory explanation for the movement time-IQ correlation is lacking. Higher IQ persons perhaps process information faster and move faster because of central underlying physiological differences affecting both information processing and speed of movement (Buckhalt et al. 1990; Tomporowski & Simpson 1990). In spite of these hypothetical disagreements, strong empirical evidence exists showing the relationship between reaction time variables and IQ (Buckhalt et al. 1990; Era et al. 1986; Geary & Widaman 1987; Jensen & Munro 1979; Jensen & Vernon 1986; Lindley et al. 1988; Matthews & Dorn 1989; Neubauer 1990).
3. Temporary Weakness of Information Processing and Accidental Injuries 3.1 Alcohol and Drugs Both alcohol drinking and drugs are associated with increased accident risk (Martens et al. 1991; Raffle 1989; Smith et al. 1989). The adverse effects of alcohol drinking (Baylor et al. 1989; Farrimond 1990; Home & Gibbons 1991; Maylor et al. 1989; Mongrain & Standing 1989) and drugs (Hindmarch 1990; Hindmarch & Harrison 1989; Kuitunen et al. 1990; Mattila & Mattila 1990) on perception, attention, thinking and psychomotor speed of reaction are widely known. Therefore, accidents due to alcohol drinking or drugs are an example of the relation between temporary weakness of information processing and accidental injuries. 3.2 Specific Motor Skills Among Beginners In many types of sports, beginners are at high risk of an injury (Bernard et al. 1988; Berson et al. 1981; Sedgwick et al. 1988; Ungerholm & Gustafsson 1985). Lack of specific coordination needed in the type of activity evidently predisposes to an injury. In beginners, the simple activity-specific motor programmes require excessive efforts of cog-
nitive processing, even though the motor skills do not respond the skills of experienced sportspeople. Therefore, among the beginners accidents may well be induced by transitory weakness of perceptual or cognitive processing variables of the individual. As the activity-specific motor programmes (skills) are incorporated by means of practice, more attention can be paid on the information exchange between the participant and the environment and the risk of injury declines subsequently. 3.3 Stressful Life Events Hinkle and Wolff (1958) and Holmes and Rahe (1967) proposed that the onset of illness often follows an increase in stressful life events. Later studies concerning accidental injuries supported the conclusion (Bramwell et al. 1975; Coddington & Troxell 1980; Cryan & Alles 1983; Hardy & Riehl 1988; Kerr & Minden 1988; Lysens et al. 1986; Passer & Seese 1983). Some authors have related individuals' insufficient coping resources to the risk of an injury during a high life stress (Coddington & Troxell 1980; Lysens et al. 1986). Lysens et al. (1986) also proposed that life stress would impair concentration. Kerr and Fowler (1988) suggested that life stress would cause both physical and mental fatigue. Concurrent memory load, which decreases cognitive resources, slows reaction time (Logan 1979). Therefore, it may be that during a stressful life event, the higher level of control is disturbed in information processing and, consequently, speed of information processing is decelerated (see fig. 2). 3.4 Fatigue Kerr and Minden (1988) asked injured female gymnasts the perceived cause of injury which was reported to be physical fatigue in 9% of cases. It is reasonable to consider any of the symptoms of fatigue, such as impairment of perception, attention, thinking, motivation and performance, to disturb control in information processing (see fig 2).
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3.5 Control of Emotions Poor control of emotions predicted automobile driving accidents in young drivers (Hilakivi et al. 1989). Perception, attention, motivation and thinking may be disturbed in unstable subjects in situations that involve strong emotions. Accordingly, poor control of emotions may disturb the higher level of control in information processing (see fig. 2).
4. Conclusions Decreased cognitive abilities seem to predispose to accidents. Both long reaction time and low grade IQ test results are associated with accidents (O'Toole 1990; Taimela 1990, 1992; Taimela et al. 1991a). Complexity of the information exchange between man and his environment is a contributor in the outcome of occupational accidents (Saari et al. 1981), and it may well be that some accidents are induced by weakness of perceptual or cognitive processing variables of the individual. Subjects may face a high risk of injury because of temporary weakening in information processing through, for example, stress, fatigue or lack of control of emotions. Especiallyconscious attention and, sequentially, resource allocation to the lower level of control may be affected (see fig. 2). Also, people with low grade intelligence may constantly have a poorer ability to assess accident risks, or they may take risks under conditions that a more intelligent person would avoid (O'Toole 1990). Inadequate speed of information processing may have a major contribution in the outcome of an accident in an unexpected situation that can result in an injury. However, there is only scant evidence that involvement in accidents increases with decreased cognitive abilities. Most studies have shown an association between information processing variables and less severe musculoskeletal injuries. Most empirical studies have been cross-sectional. In addition, no intervention trial has been done, i.e. there is no evidence that the recognition of decreased cognitive abilities, and high risk people subsequently, would have significance in acci-
dent prevention. Moreover, the relationship between cognitive processing and accidents in sports has not been studied. Some studies have reported shorter reaction times in athletes compared with nonathletes, or in athletes participating in higher levels of activity within athletes (Christenson & Winkelstein 1988; Harbin et al. 1989; Mero et al. 1989; Taimela et al. 1990b). It is still not known if speed of reaction improves in physical activities or if athletes are chosen into different activity levels due to variations in psychomotor speed. Efficient cognitive processing plays a major role in a successful outcome in most sports. The subjects with low grade mental processing, and consequently in high risk of an accident, may not participate in competitive sports due to 'a natural selection'. Accordingly, individual differences in cognitive processing may not be as significant in competitive sports as they seem to be in proneness to accidents in industry, in traffic and in noncompetitive leisure-time activities. However, prevention of sports injuries is an important objective because of their fairly high frequency (de Loes & Goldie 1988; Lattila et al. 1982; Lindqvist 1989; Sandelin et at. 1987) and expensiveness (de Loes 1990). Further studies are needed on the aetiological factors in sports injuries. As lowgrade information processing apparently predisposes to accidents, studies will be needed on the relation between cognitive processing variables and accidents in sports.
References Backx FJG, Beijer HJM, Bol E, Erich WBM. Injuries in high-risk persons and high-risk sports. American Journal of Sports Medicine 19: 124-130, 1991 Baylor AM, Spirduso WW. Systematic aerobic exercise and components of reaction time in older women. Journal of Gerontology 43: 121-126, 1988 Baylor AM, Layne CS, Mayfield RD, Osborne L, Spirduso WW. Effects of ethanol on human fractionated response times. Drug and Alcohol Dependence 23: 31-40, 1989 Beck JL, Day RW. Overuse injuries. Clinics in Sports Medicine 4: 553-573, 1985 Beck JL, Wildermuth BP. The female athlete's knee. Clinics in Sports Medicine 4: 345-366, 1985 Beh He. Reaction time and movement time after active and passive smoking. Perceptual and Motor Skills 68: 513-514, 1989 Bergenudd H, Nilsson B. Back pain in middle age: occupational
Information Processing and Accidental Injuries
workload and psychologic factors: an epidemiologic survey. Spine 13: 58-60, 1988 Bergenudd H, Lindgarde F, Nilsson B, Petersson CJ. Shoulder pain in middle age: a study of prevalence and relation to occupational work load and psychosocial factors. Clinical Orthopaedics and Related Research 231: 234-238, 1988 Bergenudd H, Nilsson B, Lindgarde F. Knee pain in middle age and its relationships to occupational work load and psychosocial factors. Clinical Orthopaedics and Related Research 245: 210-215, 1989 Bernard AA, Corlett S, Thomsen E, Bell N, McMahon A, et al. Ice skating accidents and injuries. Injury 19: 191-192, 1988 Berson BL, Rolnick AM, Ramos CG, Thornton J. An epidemiologic study of squash injuries. American Journal of Sports Medicine 9: 103-106, 1981 Bramwell ST, Masuda M, Wagner NN, Holmes TH. Psychosocial factors in athletic injuries. Journal of Human Stress 1: 6-20, 1975 Brebner JMT, Welford AT. Introduction: an historical background sketch. In Welford (Ed.) Reaction times, pp. 1-24, Academic Press, London, 1980 Buckhalt JA, Reeve TG, Dornier LA. Correlations of movement time and intelligence: effects of simplifying response requirements. Intelligence 14: 481-491, 1990 Buros OK. The eighth mental measurements yearbook, Gryphon Press, Highland Park, 1978 Cattell RB, Cattell AKS. Handbook for the individual or culture fair intelligence test: scale 2, IPAT, Champaign, 1960 Child D. The essentials of factor analysis, Holt, Rinehart & Winston, London, 1970 Chodzko-Zajko WJ, Ringel R. Physiological fitness measures and sensory and motor performance in aging. Experimental Gerontology 22: 317-328, 1987 Christenson GN, Winkelstein AM. Visual skills of athletes versus nonathletes: development of a sports vision testing battery. Journal of the American Optometric Association 59: 666-675, 1988 Clarkson-Smith L, Hartley AA. Relationships between physical exercise and cognitive abilities in older adults. Psychology and Aging 4: 183-189, 1989 Clement DB, Taunton JE, Smart GW, McNicol KL. A survey of overuse running injuries. Physician and Sportsmedicine 9: 4758, 1981 Coddington RD, Troxell JR. The effect of emotional factors on football injury rates - a pilot study. Journal of Human Stress 6: 3-5, 1980 Cronbach U. Essentials of psychological testing, Harper & Row, New York, 1970 Cryan PO, Alles WF. The relationship between stress and college football injuries. Journal of Sports Medicine and Physical Fitness 23: 52-58, 1983 de Loes M. Medical treatment and costs of sports-related injuries in total population. International Journal of Sports Medicine II: 66-72, 1990 de Loes M, Goldie I. Incidence rate of injuries during sport activity and physical exercise in a rural Swedish municipality: incidence rates in 17 sports. International Journal of Sports Medicine 9: 461-467, 1988 Dickinson J. The training of mobile balancing under a minimal visual cue situation. Ergonomics II: 69-75, 1968 Edwards RHT. Hypotheses of peripheral and central mechanisms underlying occupational muscle pain and injury. European Journal of Applied Physiology 57: 275-281, 1988 Ekstrand J, Gillquist J. The avoidability of soccer injuries. International Journal of Sports Medicine 4: 124-128, 1983a Ekstrand J, Gillquist J. Soccer injuries and their mechanisms: a prospective study. Medicine and Science in Sports and Exercise 15: 267-270, 1983b Ekstrand J, Gillquist J, Liljedahl SO. Prevention of soccer inju-
373
ries: supervision by doctor and physiotherapist. American Journal of Sports Medicine II: 116-120, 1983 Era P, Jokela J, Heikkinen E. Reaction and movement times in men of different ages: a population study. Perceptual and Motor Skills 63: 111-130, 1986 Farrimond T. Effect of alcohol on visual constancy values and possible relation to driving performance. Perceptual and Motor Skills 70: 291-295, 1990 Forth CD, Salmoni AW. Relationships among self-reported physical activity, aerobic fitness and reaction time. Canadian Journal of Sports Sciences 13: 88-90, 1988 Geary DC, Widaman KF. Individual differences in cognitive arithmetic. Journal of Experimental Psychology [General] 116: 154-171, 1987 Grace TG, Skipper BJ, Newberry JC, Nelson MA, Sweetser ER, et al. Prophylactic knee braces and injury to the lower extremity. Journal of Bone and Joint Surgery 70-A: 422-427, 1988 Guilford JP. The nature of human intelligence, McGraw-Hill, London, 1971 Harbin G, Durst L, Harbin D. Evaluation ofoculomotor response in relationship to sports performance. Medicine and Science in Sports and Exercise 21: 258-262, 1989 Hardy CJ, Riehl RE. An examination of the life stress-injury relationship among noncontact sport participants. Behavioral Medicine 14: 113-118, 1988 Heckel RV, Allen SS, Andrews L, Roeder G, Ryba P, et al. Normative data on the Kagan Matching Familiar Figures test for adult male incarcerates. Journal of Clinical Psychology 45: 155160, 1989 Heim AW, Watts KP, Simmons V. AH2/AH3 manual, NFER, Windsor, 1974 Henry FM. Reaction time and movement time correlations. Perceptual and Motor Skills 12: 63-66, 1961 Hick WE. On the rate of gain of information. Quarterly Journal of Experimental Psychology 4: 11-26, 1952 Hilakivi I, Veilahti J, Asplund P, Sinivuo J, Laitinen L, et al. A sixteen-factor personality test for predicting automobile driving accidents of young drivers. Accident Analysis and Prevention 21: 413-418, 1989 Hill RD. Residual effects of cigarette smoking on cognitive performance in normal aging. Psychology and Aging 4: 251-254, 1989 Hindmarch I. Immediate and overnight effects ofzopiclone 7.5mg and nikazepam 5mg with ethanol, on psychomotor performance and memory in healthy volunteers. International Clinical Psychopharmacology 5 (Suppl. 2): 105-113, 1990 Hindmarch I, Harrison C. The effects of paroxetine and other antidepressants in combination with alcohol on psychomotor activity related to car driving. Acta Psychiatrica Scandinavica 350: 45, 1989 Hinkle LE, Wolff HG. Ecologic investigations ofthe relationship between illness, life experiences and the social environment. New England Journal of Medicine 49: 1373-1388, 1958 Hodgkins J. Reaction time and speed of movement in males and females of various ages. Research Quarterly 34: 335-343, 1963 Holmes TH, Rahe RH. The social readjustment rating scale. Journal of Psychosomatic Research 11: 213-218,1967 Home JA, Gibbons H. Effects on vigilance performance and sleepiness of alcohol given in the early afternoon ('post lunch') vs. early evening. Ergonomics 34: 67-77, 1991 Hughes JR, Keenan RM, Yellin A. Effects of tobacco withdrawal on sustained attention: Addictive Behaviors 14: 577-580, 1989 Hulkko A. Stress fractures in athletes, academic dissertation, University of Oulu, Oulu, 1988 Inkelis SH, Stroberg AJ, Keller EL, Christenson PD. Roller skating injuries in children. Pediatric Emergency Care 4: 127-132, 1988 Jackson OW, Jarrett H, Bailey 0, Kausek J, Swanson J, et al.
374
Injury prediction in the young athlete: a preliminary report. American Journal of Sports Medicine 6: 6-14, 1978 James SL, Bates BT, Osternig LR. Injuries to runners. American Journal of Sports Medicine 6: 40-50, 1978 Jensen AR, Munro E. Reaction time, movement time and intelligence. Intelligence 3: 121-126, 1979 Jensen AR, Vernon PA. Jensen's reaction-time studies: a reply to Longstreth. Intelligence 10: 153-179, 1986 Jordan T'C, Characteristics of visual and proprioceptive response times in the learning of a motor skill. Quarterly Journal of Experimental Psychology 24: 536-543, 1972 Kamen G, Morris HH. Differences in sensorimotor processing of visual and proprioceptive stimuli. Research Quarterly 59: 2934, 1988 Kelley MJ. Psychological risk factors and sports injuries. Journal of Sports Medicine and Physical Fitness 30: 202-221, 1990 Kerr G, Fowler B. The relationship between psychological factors and sports injuries. Sports Medicine 6: 127-134, 1988 Kerr G, Minden H. Psychosocial factors related to the occurrence of athletic injuries. Journal of Sport and Exercise Psychology 10: 167-173, 1988 Kilburn KH, Warshaw R, Thornton JC, Husmark I. An examination of factors that could affect choice reaction time in histology technicians. American Journal of Industrial Medicine 15: 679-686, 1989 Klein RM, Posner MI. Attention to visual and kinaesthetic components of skills. Brain Research 71 : 401-411, 1974 Kuitunen T, Mattila MJ, Seppala T. Actions and interactions of hypnotics on human performance: single doses of zopiclone, triazolam and alcohol. International Clinical Psychopharmacology 5 (Suppl. 2): 115-130, 1990 Kujala UM. Knee exertion injuries in adolescents and young adults: a study with special reference to anatomic predisposition, Publications of the Social Insurance Institution, Finland, Turku, 1986 Kujala UM, Heinonen OJ, Lehto M, Jarvinen M, Bergfeld JA. Equipment, drugs and problems of the competition and team physician. Sports Medicine 6: 197-209, 1988 Lattila R, Heiskanen T, Komulainen R, Niskanen T, Siren R. Tapaturmat ja vakivalta 1980 (accidents and violence 1980), Central Statistical Office of Finland, Helsinki, 1982 Lindley RH, Smith WR, Thomas TJ. The relationship between speed of information processing as measured by timed paperand-pencil tests and psychometric intelligence. Intelligence 12: 17-25, 1988 Lindqvist KS. Epidemiology of accidents in a Swedish municipality. Accident Analysis and Prevention 21: 33-43, 1989 Logan GO. On the use of a concurrent memory load to measure attention and automaticity. Journal of Experimental Psychology - Human Perception and Performance 5: 189-207, 1979 Lysens R, Stevernlynck A, van den Auweele Y, Lefevre J, Renson L, et al. The predictability of sports injuries. Sports Medicine I: 6-10, 1984 Lysens R, van den Auweele Y, Ostyn M. The relationship between psychosocial factors and sports injuries. Journal of Sports Medicine and Physical Fitness 26: 77-84, 1986 Lysens R, Ostyn MS, vanden Auweele Y, Lefevre J, Vuylsteke M, et al. The accident-prone and overuse-prone profiles of the young athlete. American Journal of Sports Medicine 17: 612619, 1989 Marteniuk ltG. Information processing in motor skills, Holt, Rinehart and Winston, New York, 1976 Martens CH, Ross LE, Mundt Je. Young drivers' evaluation of driving impairment due to alcohol. Accident Analysis and Prevention 23: 67-76, 1991 Matthews G, Oorn L. IQ and choice reaction time: an information processing analysis. Intelligence 13: 299-317, 1989 Mattila MJ, Mattila ME. Effects of remoxipride on psychomotor
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performance, alone and in combination with ethanol and diazepam. Acta Psychiatrica Scandinavica 358: 54-55, 1990 Maylor EA, Rabbitt PM, Connolly SA. Rate of processing and judgment of response speed: comparing the effects of alcohol and practice. Perception and Psychophysics 45: 431-438, 1989 McKenzie DC, Clement DB, Taunton JE. Running shoes, orthotics and injuries. Sports Medicine 2: 334-347, 1985 Mero A, Jaakkola L, Komi PV. Neuromuscular, metabolic and hormonal profiles of young tennis players and untrained boys. Journal of Sports Sciences 7: 95-100, 1989 Mongrain S, Standing L. Impairment of cognition, risk-taking, and self-perception by alcohol. Perceptual and Motor Skills 69: 199-210, 1989 Neubauer Ae. Selective reaction times and intelligence. Intelligence 14: 79-96, 1990 O'Toole BI. Intelligence and behaviour and motor vehicle accident mortality. Accident Analysis and Prevention 22: 211-221, 1990 Passer MW, Seese MD. Life stress and athletic injury: examination of positive versus negative events and three moderator variables. Journal of Human Stress 9: 11-16, 1983 Persaud G, Salmon HM. Factor structure of newly designed verbal tests. Perceptual and Motor Skills 67: 123-128, 1988 Rabbitt P, Banerji N. How does very prolonged practice improve decision speed? Journal of Experimental Psychology [General] 118: 338-345, 1989 Raffle PA. Interrelation between alcohol and accidents. Journal of the Royal Society of Health 82: 132-135, 1989 Raven Je. Advanced Progressive Matrices: sets I and 2, Lewis & Co, London, 1965 Robey JM, Blyth CS, Mueller Fa. Athletic injuries: application of epidemiologic methods. Journal of American Medical Association 217: 184-189, 1971 Saari J, Tech 0, Lahtela J. Work conditions and accidents in three industries. Scandinavian Journal of Work, Environment and Health 7 (Suppl. 4): 97-105, 1981 Sandelin J, Santavirta S, Lattila R, Vuolle P, Sarna S. Sport injuries in a large urban population: occurrence and epidemiologic aspects. International Journal of Sports Medicine 8: 6166, 1987 Sanders AF. Towards a model of stress and human performance. Acta Physiologica 53: 61-97, 1983 Schmidt RA. Motor control and learning: a behavioral emphasis, Human Kinetics Publishers, Champaign, 1988 Sedgwick AW, Smith OS, Davies MJ. Musculoskeletal status of men and women who entered a fitness programme. Medical Journal of Australia 148: 385-399, 1988 Slack WV, Leviton A, Bennett SE, Fleischmann KH, Lawrence RS. Relation between age, education, and time to respond to questions in a computer-based medical interview. Computers and Biomechanical Research 21: 78-84, 1988 Smith GA. Models of reaction time. In Welford (Ed.) Reaction times, pp. 173-214, Academic Press, London, 1980 Smith SM, Goodman RA, Thacker SB, Burton AH, Parsons JE, et al. Alcohol and fatal injuries: temporal patterns. American Journal of Preventive Medicine 5: 296-302, 1989 Snyder FR, Henningfield JE. Effects of nicotine administration following 12h of tobacco deprivation: assessment on computerized performance tasks. Psychopharmacology 97: 17-22, 1989 Stelmach GE, Goggin NL, Garcia-Corea A. Movement specification time with age. Experimental Aging Research 13: 39-46, 1987 Taerk GS. The injury-prone athlete: a psychosocial approach. Journal of Sports Medicine and Physical Fitness 17: 187-194, 1977 Taimela S. Relation between speed of reaction and psychometric tests of mental ability in musculoskeletal injury-prone subjects. Perceptual and Motor Skills 70: 155-161, 1990
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Taimela S. Choice reaction time, intelligence and accidental injuries. Submitted, 1992 Taimela S. Factors affecting reaction time testing and the interpretation of the results. Perceptual Motor Skills 73: 1195-2002, 1991 Taimela S, Kujala UM, Osterman K. Intrinsic risk factors and athletic injuries. Sports Medicine 9: 205-215, 1990a Taimela S, Osterman K, Kujala UM, Lehto M, Korhonen T, et al. Motor ability and personality with reference to soccer injuries. Journal of Sports Medicine and Physical Fitness 30: 194201, 1990b Taimela S, Kujala UM, Osterman K. The relation of low grade mental ability to fractures in young men. International Orthopaedics 15: 75-77, 1991a Taimela S, Osterman K, Alaranta H, Soukka A, Kujala UM. Long psychomotor reaction time in patients with chronic low-back pain - a preliminary report. Archives of Physical Medicine and Rehabilitation, in press, 1992 Tomporowski PO, Simpson RG. Sustained attention and intelligence. Intelligence 14: 31-42, 1990 Torg JS, Vegso JJ, Sennelt B, Das M. The national football head and neck injury registry. Journal of the American Medical Association 254: 3439-3443, 1985 Ungerholm S, Gustafsson J. Skiing safety in children: a prospective study of downhill skiing injuries and their relation to the
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skier and his equipment. International Journal of Sports Medicine 6: 353-358, 1985 Valliant PM. Personality and injury in competitive runners. Perceptual and Motor Skills 53: 251-253, 1981 Van Mechelen W, Hlobil H, Kemper HCG. How can sport injuries be prevented? National Institute for Sports Health Care, Oosterbeek, The Netherlands, 1987 Watson AWS. Sports injuries during one academic year in 6799 Irish school children. American Journal of Sports Medicine 12: 65-71, 1984 Wechsler D. The measurement and appraisal of adult intelligence, Williams and Wilkins, Baltimore, 1958 Welford AT. Choice reaction time: basic concepts. In Welford (Ed.) Reaction times, pp. 73-128, Academic Press, London, 1980a Welford AT. Relationships between reaction time and fatigue, stress, age and sex. In Welford (Ed.) Reaction times, pp. 321354, Academic Press, London, 1980b Widaman KF, Carlson JS. Procedural effects of performance on the Hick paradigm: bias in reaction time and movement time parameters. Intelligence 13: 63-85, 1989 Correspondence and reprints: Dr Sima Taimela, Helsinki Research Institute for Sports and Exercise Medicine, Toolan Kisahalli, Mannerheimintie 17, SF-00250, Helsinki, Finland.
Sports Medicine 14 (6): 366-375, 1992 0112-1642/92/0012-0366/$05.00/0 © Adis International Limited. All rights reserved . SP01186
Information Processing and Accidental Injuries Sima Taimela Helsinki Research Institute for Sports and Exercise Medicine, Helsinki, Finland
The prevention of sports injuries is an important objective in the reduction of accidental injuries (de Loes & Goldie 1988; Lattila et al. 1982; Lindqvist 1989; Sandelin et al. 1987). Sports accidents are costly for society and the injured individual (de Loes 1990). Four areas can be identified in the sports injury prevention (Backx et al. 1991; Van Mechelen et al. 1987). The first area includes the analysis of the nature, extent and severity of sports injuries. Secondly, the aetiological factors involved in sports injuries are identified. Thirdly, the application of preventive measures is done , followed by analysis of the effects ofthe preventive measures. However, very few studies have looked at aetiological factors and preventative measures (Ekstrand & Gillquist 1983a; Torg et al. 1985). Several aetiological factors involved in sports injuries have been analysed (Backx et al. 1991; Lysens et al. 1989; Taimela et al. 1990a). Commonly, injury risk factors in sports are classified as activity related (extrinsic factors) and participant related (intrinsic factors). Each type of activity has its characteristic injury profile and degree of risk and the type of injuries varies widely (de Loes & Goldie 1988; Kujala et al. 1988). Extrinsic injury risk factors include, for example, training errors (Clement et al. 1981; McKenzie et al. 1985; Sedgwick et al. 1988) and environmental conditions, such as terrain, weather and equipment (Ekstrand & Gillquist 1983b; Ekstrand et al. 1983; Grace et al. 1988; Hulkko 1988; James et aI. 1978; McKenzie et al. 1985). The participant re-
lated injury risk factors include abnormal anatomy or biomechanics (Kujala 1986; Lysens et al. 1989), poor aerobic or muscle conditioning (Kerr & Minden 1988; Watson 1984),former injuries (Ekstrand & Gillquist 1983b; Lysens et al. 1984; Robey et al. 1971), psychological factors (Jackson et al. 1978; Taerk 1977; Valliant 1981) and accumulation of life stress (Bramwell et al. 1975; Coddington & Troxell 1980; Cryan & Alles 1983; Kerr & Minden 1988; Passer & Seese 1983). There are few studies concerning the relationship between central motor control and sports injuries even though it is presumable that low grade motor control predisposes to accidental injury. It has also been suggested in some papers that poor coordination and slow psychomotor speed predispose to injury (Beck & Day 1985; Beck & Wildermuth 1985; Edwards 1988; Inkelis et al. 1988; Kelley 1990) and some experimental evidence has been recently gained also with regard to the hypothesis. This review discusses findings on information processing and the musculoskeletal injuries to-date and offers suggestions for future study. The concept of central motor control is presented in detail as it represents an essential part of information processing requirements in sports.
1. Information Processing Variables and Injuries: Existing Literature Low grade intelligence quotient (IQ) and slow choice reaction time were related to history of accidental bone fracture in young men (Taimela 1990;
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Taimela et al. 1991a). The study group included a sample of 123 army conscripts who were interviewed for previous accidents and tested for IQ and reaction time . Eight bone fractures were recorded during the previous 20 months in the subjects. The fracture group gained poorer results both in all the components of IQ tested and in slow choice reaction time. Because of the small number of injuries, the study was repeated in a sample of 823 army conscripts using the same tests. Again, low grade arithmetic ability and slow reaction time were related to accident history (Taimela 1992). Low grade army intelligence test result was predictive of motor vehicle accident mortality in the Australian troops during the Vietnam war (O'Toole 1990). Individuals with back pain (Bergenudd & Nilsson 1988), knee pain (Bergenudd et al. 1989), and shoulder pain (Bergenudd et al. 1988) in middle age had been less successful in a childhood intelligence test than individuals with no musculoskeletal complaints. Unfortunately, single accidents were not considered in the study group. Subjects with chronic low back pain were slower in a reaction time test than controls in a preliminary study (Taimela et al. 1992). However, long reaction time may be a consequence of back pain instead of the cause. Simple reaction time was associated with injuries in soccer (Taimela et al. 1990b). Unfortunately, neither choice reaction time nor IQ was tested in this study. Generally, an association between reaction time and IQ variables and injuries has repeatedly been found. However, most studies have shown an association between information processing variables and less severe injuries only. Further studies are needed on the association between information processing variables and severe injuries .
Stimulus
. ~
Stimulus identification
2. Central Motor Control: The Concept of Information Processing Humans are considered as processors of information (Marteniuk 1976; Schmidt 1988; Smith 1980). In this concept , information from the environment is obtained by specific sense organs and processed. Commonly, the processing is considered to include stimulus identification, response selection and response programming (fig. I) [Marteniuk 1976; Matthews & Dom 1989; Schmidt 1988; Smith 1980]. Accordingly, human movements may be considered as responses to the environmental stimuli . However, the simple signal-response model is sufficient to explain only the most simple movements; it is incompetent in interpreting complex continuous or serial movements, or multiple simultaneous tasks.. More sophisticated models of human motor functioning have accordingly been presented . A 2-stage model of information processing includes at the lower level stimulus processing, feature extraction, response choice and motor adjustment (Matthews & Dom 1989; Sanders 1983). The higher level of control includes, for example, memory load, arousal , conscious att ention and resource distribution (fig. 2) [Matthews & Dom 1989; Sanders 1983; Schmidt 1988]. These response models, however, must be considered as simplifications of complex human motor behaviour. Three different techniques may be described in the measurement of motor responses: speed, accuracy, and magnitude of the movements (Schmidt 1988). Perhaps the most common approach is to consider the duration of the various information processes. . Fundamental to the measurement of speed is the assumption that the person who can
Response selection
Fig. 1. A simplified information processing model (after Schmidt 1988).
Response programming
Response
.
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execute more repetitions in a limited amount of time, or who can produce the specified behaviour in less time, is the more skilful. 2.1 Speed of Information Processing Psychomotor speed of reaction, i.e. the time from the onset of an unexpected stimulus to the initiation of the response, has been recognised as a means of relating mental events to physical measures since the nineteenth century. Reaction time measures are common in research for 2 primary reasons. First, reaction time measures are components of real life tasks, especially in sports and in traffic. Secondly, reaction times measure the time taken for mental events, such as stimulus processing, decision making and response programming (Marteniuk 1976; Matthews & Dorn 1989; Schmidt 1988; Smith 1980). Conventional methods in the assessment of reaction times have been apparatus tests involving motor response to visual stimuli (fig. 3). Simple reaction time, in which there is only I signal and corresponding response, is usually distinguished from choice reaction time. In reaction time, there are several signals and corresponding responses. Reaction times are also often differentiated into decision and movement time. Decision time is the interval between the arrival of the signal and the beginning of response to it, and movement time, the interval from the initia-
Attention
tion of the response to the completion of the movement (fig. 4). 2.1.1 Testing of Reaction Times Several factors associated with the equipment and testing facilities have an effect on reaction time test results. These determinants include (I) sensory factors, such as intensity of the stimulus; (2) response characteristics, such as size and distance of the target; (3) preparation, i.e. possible warning signal before the stimulus and length of the foreperiod; and (4) complexity of the choice (Brebner & Welford 1980; Rabbitt & Banerji 1989; Schmidt 1988; Welford I980a). Choice reaction time is linearly related to the log of the number of stimulus alternatives, the relation being known as Hick's law (Hick 1952; Schmidt 1988; Welford I980a). The amount of practice before the trial is a major contributor in the reaction time test results also (Rabbitt & Banerji 1989; Welford I980a). The dominance of visual sense has been noticed in several studies (Dickinson 1968; Jordan 1972; Kamen & Morris 1988;Klein & Posner 1974). Reaction times vary across the sensory modalities while, for example, auditive and proprioceptive reaction times are shorter than visual reaction times and vestibular stimuli produce long reaction times (Brebner & Welford 1980; Kamen & Morris 1988). These variations may rise from differences in peripheral sensory mechanisms rather than from the central processing of the information (Brebner & Welford
Arousal
Memory load
Resources
Resource allocation ~r
Stimulus ...
...
Stimulus identification
~Ir
Feature extraction
Response selection
Response programm ing
Response
.....
Fig. 2. A 2-stage information processing model (after Marteniuk 1976; Matthews & Dorn 1989; Schmidt 1988; Smith 1980).
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• K2
o
K3
L3
L2
•
o
Attention light
•
0
L1
Kt
o
Standby button
L4
0
• K4
Fig. 3. Choice reaction time apparatus: a schematic presentation. Ll, L2, etc. = stimulus light I, 2, etc.; Kl, K2, etc. = corresponding key. A finger is held ready on the standby button in the beginning of the test. When the attention light is turned on the subject focuses his/her attention. When the stimulus light is turned on, the subject releases the standb y button and presses the button corresponding to the stimulus as fast as possible. The speed of decision is measured as the interval between the appearance of the stimulus and release of the standby button . The speed of movement is measured by the interval between releasing the standby button and pressing the button corresponding to the stimulus. Mean decision and movement times are calculated from several recorded attempts. The total choice reaction time (CRT) is calculated as an arithmetic sum of the decision and movement times.
1980). For example, there are differences in afferent conduction times . Currently, however, no definite evidence can be shown to demonstrate that the central decision component of reaction time is similar in all the sensory modalities. It has also been suggested that the nature of the stimulus which initiates the response may affect central processing requirements to initiate the response (Kamen & Morris 1988). 2.1.2 Subject-Related Factors Affecting Reaction Times Subject-related factors that may affect reaction time include age and gender. Men are faster than women in both reaction and movement, and speed of both functions increases up to early adulthood and then decreases in all the levels of test complexity (Chodzko-Zajko & Ringel 1987; Era et al. 1986; Hodgkins 1963; Stelmach et al. 1987; Welford 1980b). The contribution of age in the reac-
tion time test results in the age group 17 to 30 years is minimal (Taimela 1991b). Many studies have shown a relation between slow reaction time variables and low grade IQ (Buckhalt et al. 1990; Era et al. 1986; Geary & Widaman 1987; Jensen & Munro 1979; Jensen & Vernon 1986; Lindley et al. 1988;Matthews & Dorn 1989;Neubauer 1990). The relation between IQ and reaction time is consistent in both decision time and in movement time regardless of task complexity (Buckhalt et al. 1990; Neubauer 1990). Educational , occupational or lifestyle factors and smoking may have some influence on reaction times. The results of occupational and educational factors in reaction times have been disputed (Heckel et al. 1989; Kilburn et al. 1989; Slack et al. 1988). Systematic physical activity and short reaction times are related in older age groups only (Baylor & Spirduso 1988; Chodzko-Zajko & Ringel 1987; Clarkson-Smith & Hartley 1989; Forth & Salmoni 1988). Prolonged tobacco deprivation
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RT
Warning
MT
DT
Foreperiod
Stimulus
t
Start of response
Endof response
f
Fig. 4. Components of reaction time (RT = reaction time; DT = decision time; MT = movement time).
lengthens reaction times in smokers, but no difference has been found between smokers and nonsmokers in reaction times (Beh 1989; Hill 1989; Hughes et al. 1989; Snyder & Henningfield 1989). Some studies have reported differences in reaction times between athletes and nonathletes or between different levels of activity within athletes (Christenson & Winkelstein 1988; Harbin et al. 1989; Mero et al. 1989; Taimela et al. 1990b). It is still not known if speed of reaction improves in physical activities or if athletes are chosen into different activity levels because of variations in psychomotor speed.
have been widely used. These tests make objective testing of intellectual performance possible (Buros 1978; Cronbach 1970; Guilford 1971; Wechsler 1958). Some examples of widely used tests are Cattells' Culture Fair Intelligence Test (1960), Raven's Advanced Progressive Matrices (1965) and AH2 and AH3 tests of general reasoning (Heim et al. 1974). The tests are measures of traditional intelligence or convergent thinking in contrast to tests of creativity (Child 1970; Guilford 1971; Persaud & Salmon 1988). The IQ tests commonly include subtests for at least spatial, verbal and arithmetic ability and a total score.
2.2 The Concept of Intelligence Many psychometric intelligence quotient (lQ) tests that utilise paper and pencil have been developed during the last few decades (Buros 1978). Most tests are descendants of the Wechsler Adult Intelligence Scale (WAIS) [Wechsler 1958], thus, originally descendants of Binet's intelligence scale from the nineteenth century. As there is no general agreement concerning IQ testing, different components of intelligence have been analysed. Verbal and arithmetic ability and performance in image tests are the conventional tests. Factor speed plays an important role in the IQ tests, that is, the tests reflecting both speed of recognition of structures and speed of performance. Information, comprehension, arithmetics, similarities, vocabulary, block design, picture completion, picture arrangement, object assembly and coding are some subtests that
2.3 The Relationship Between Reaction Time and IQ A few hypothetical questions concerning the IQreaction time relationship are uncertain. It is not known if these processes are associated with some global characteristic of the mind or with some specific processing modules. The 2-stage model of reaction time includes at the lower level stimulus processing, feature extraction, response choice and motor adjustment (fig. 2). The higher level of control includes memory load, conscious attention and resource distribution (Matthews & Dorn 1989; Sanders 1983). The participation of the different levels of control in IQ and complex reaction time remains unresolved. Many studies have shown essentially zero correlations between reaction time and movement time (Henry 1961; Schmidt 1988),
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suggesting that they are based on separate abilities. However, higher correlations between movement time and IQ have been reported than between decision time and IQ independent of task complexity (Buckhalt et al. 1990; Neubauer 1990; Widaman & Carlson 1989). A satisfactory explanation for the movement time-IQ correlation is lacking. Higher IQ persons perhaps process information faster and move faster because of central underlying physiological differences affecting both information processing and speed of movement (Buckhalt et al. 1990; Tomporowski & Simpson 1990). In spite of these hypothetical disagreements, strong empirical evidence exists showing the relationship between reaction time variables and IQ (Buckhalt et al. 1990; Era et al. 1986; Geary & Widaman 1987; Jensen & Munro 1979; Jensen & Vernon 1986; Lindley et al. 1988; Matthews & Dorn 1989; Neubauer 1990).
3. Temporary Weakness of Information Processing and Accidental Injuries 3.1 Alcohol and Drugs Both alcohol drinking and drugs are associated with increased accident risk (Martens et al. 1991; Raffle 1989; Smith et al. 1989). The adverse effects of alcohol drinking (Baylor et al. 1989; Farrimond 1990; Home & Gibbons 1991; Maylor et al. 1989; Mongrain & Standing 1989) and drugs (Hindmarch 1990; Hindmarch & Harrison 1989; Kuitunen et al. 1990; Mattila & Mattila 1990) on perception, attention, thinking and psychomotor speed of reaction are widely known. Therefore, accidents due to alcohol drinking or drugs are an example of the relation between temporary weakness of information processing and accidental injuries. 3.2 Specific Motor Skills Among Beginners In many types of sports, beginners are at high risk of an injury (Bernard et al. 1988; Berson et al. 1981; Sedgwick et al. 1988; Ungerholm & Gustafsson 1985). Lack of specific coordination needed in the type of activity evidently predisposes to an injury. In beginners, the simple activity-specific motor programmes require excessive efforts of cog-
nitive processing, even though the motor skills do not respond the skills of experienced sportspeople. Therefore, among the beginners accidents may well be induced by transitory weakness of perceptual or cognitive processing variables of the individual. As the activity-specific motor programmes (skills) are incorporated by means of practice, more attention can be paid on the information exchange between the participant and the environment and the risk of injury declines subsequently. 3.3 Stressful Life Events Hinkle and Wolff (1958) and Holmes and Rahe (1967) proposed that the onset of illness often follows an increase in stressful life events. Later studies concerning accidental injuries supported the conclusion (Bramwell et al. 1975; Coddington & Troxell 1980; Cryan & Alles 1983; Hardy & Riehl 1988; Kerr & Minden 1988; Lysens et al. 1986; Passer & Seese 1983). Some authors have related individuals' insufficient coping resources to the risk of an injury during a high life stress (Coddington & Troxell 1980; Lysens et al. 1986). Lysens et al. (1986) also proposed that life stress would impair concentration. Kerr and Fowler (1988) suggested that life stress would cause both physical and mental fatigue. Concurrent memory load, which decreases cognitive resources, slows reaction time (Logan 1979). Therefore, it may be that during a stressful life event, the higher level of control is disturbed in information processing and, consequently, speed of information processing is decelerated (see fig. 2). 3.4 Fatigue Kerr and Minden (1988) asked injured female gymnasts the perceived cause of injury which was reported to be physical fatigue in 9% of cases. It is reasonable to consider any of the symptoms of fatigue, such as impairment of perception, attention, thinking, motivation and performance, to disturb control in information processing (see fig 2).
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3.5 Control of Emotions Poor control of emotions predicted automobile driving accidents in young drivers (Hilakivi et al. 1989). Perception, attention, motivation and thinking may be disturbed in unstable subjects in situations that involve strong emotions. Accordingly, poor control of emotions may disturb the higher level of control in information processing (see fig. 2).
4. Conclusions Decreased cognitive abilities seem to predispose to accidents. Both long reaction time and low grade IQ test results are associated with accidents (O'Toole 1990; Taimela 1990, 1992; Taimela et al. 1991a). Complexity of the information exchange between man and his environment is a contributor in the outcome of occupational accidents (Saari et al. 1981), and it may well be that some accidents are induced by weakness of perceptual or cognitive processing variables of the individual. Subjects may face a high risk of injury because of temporary weakening in information processing through, for example, stress, fatigue or lack of control of emotions. Especiallyconscious attention and, sequentially, resource allocation to the lower level of control may be affected (see fig. 2). Also, people with low grade intelligence may constantly have a poorer ability to assess accident risks, or they may take risks under conditions that a more intelligent person would avoid (O'Toole 1990). Inadequate speed of information processing may have a major contribution in the outcome of an accident in an unexpected situation that can result in an injury. However, there is only scant evidence that involvement in accidents increases with decreased cognitive abilities. Most studies have shown an association between information processing variables and less severe musculoskeletal injuries. Most empirical studies have been cross-sectional. In addition, no intervention trial has been done, i.e. there is no evidence that the recognition of decreased cognitive abilities, and high risk people subsequently, would have significance in acci-
dent prevention. Moreover, the relationship between cognitive processing and accidents in sports has not been studied. Some studies have reported shorter reaction times in athletes compared with nonathletes, or in athletes participating in higher levels of activity within athletes (Christenson & Winkelstein 1988; Harbin et al. 1989; Mero et al. 1989; Taimela et al. 1990b). It is still not known if speed of reaction improves in physical activities or if athletes are chosen into different activity levels due to variations in psychomotor speed. Efficient cognitive processing plays a major role in a successful outcome in most sports. The subjects with low grade mental processing, and consequently in high risk of an accident, may not participate in competitive sports due to 'a natural selection'. Accordingly, individual differences in cognitive processing may not be as significant in competitive sports as they seem to be in proneness to accidents in industry, in traffic and in noncompetitive leisure-time activities. However, prevention of sports injuries is an important objective because of their fairly high frequency (de Loes & Goldie 1988; Lattila et al. 1982; Lindqvist 1989; Sandelin et at. 1987) and expensiveness (de Loes 1990). Further studies are needed on the aetiological factors in sports injuries. As lowgrade information processing apparently predisposes to accidents, studies will be needed on the relation between cognitive processing variables and accidents in sports.
References Backx FJG, Beijer HJM, Bol E, Erich WBM. Injuries in high-risk persons and high-risk sports. American Journal of Sports Medicine 19: 124-130, 1991 Baylor AM, Spirduso WW. Systematic aerobic exercise and components of reaction time in older women. Journal of Gerontology 43: 121-126, 1988 Baylor AM, Layne CS, Mayfield RD, Osborne L, Spirduso WW. Effects of ethanol on human fractionated response times. Drug and Alcohol Dependence 23: 31-40, 1989 Beck JL, Day RW. Overuse injuries. Clinics in Sports Medicine 4: 553-573, 1985 Beck JL, Wildermuth BP. The female athlete's knee. Clinics in Sports Medicine 4: 345-366, 1985 Beh He. Reaction time and movement time after active and passive smoking. Perceptual and Motor Skills 68: 513-514, 1989 Bergenudd H, Nilsson B. Back pain in middle age: occupational
Information Processing and Accidental Injuries
workload and psychologic factors: an epidemiologic survey. Spine 13: 58-60, 1988 Bergenudd H, Lindgarde F, Nilsson B, Petersson CJ. Shoulder pain in middle age: a study of prevalence and relation to occupational work load and psychosocial factors. Clinical Orthopaedics and Related Research 231: 234-238, 1988 Bergenudd H, Nilsson B, Lindgarde F. Knee pain in middle age and its relationships to occupational work load and psychosocial factors. Clinical Orthopaedics and Related Research 245: 210-215, 1989 Bernard AA, Corlett S, Thomsen E, Bell N, McMahon A, et al. Ice skating accidents and injuries. Injury 19: 191-192, 1988 Berson BL, Rolnick AM, Ramos CG, Thornton J. An epidemiologic study of squash injuries. American Journal of Sports Medicine 9: 103-106, 1981 Bramwell ST, Masuda M, Wagner NN, Holmes TH. Psychosocial factors in athletic injuries. Journal of Human Stress 1: 6-20, 1975 Brebner JMT, Welford AT. Introduction: an historical background sketch. In Welford (Ed.) Reaction times, pp. 1-24, Academic Press, London, 1980 Buckhalt JA, Reeve TG, Dornier LA. Correlations of movement time and intelligence: effects of simplifying response requirements. Intelligence 14: 481-491, 1990 Buros OK. The eighth mental measurements yearbook, Gryphon Press, Highland Park, 1978 Cattell RB, Cattell AKS. Handbook for the individual or culture fair intelligence test: scale 2, IPAT, Champaign, 1960 Child D. The essentials of factor analysis, Holt, Rinehart & Winston, London, 1970 Chodzko-Zajko WJ, Ringel R. Physiological fitness measures and sensory and motor performance in aging. Experimental Gerontology 22: 317-328, 1987 Christenson GN, Winkelstein AM. Visual skills of athletes versus nonathletes: development of a sports vision testing battery. Journal of the American Optometric Association 59: 666-675, 1988 Clarkson-Smith L, Hartley AA. Relationships between physical exercise and cognitive abilities in older adults. Psychology and Aging 4: 183-189, 1989 Clement DB, Taunton JE, Smart GW, McNicol KL. A survey of overuse running injuries. Physician and Sportsmedicine 9: 4758, 1981 Coddington RD, Troxell JR. The effect of emotional factors on football injury rates - a pilot study. Journal of Human Stress 6: 3-5, 1980 Cronbach U. Essentials of psychological testing, Harper & Row, New York, 1970 Cryan PO, Alles WF. The relationship between stress and college football injuries. Journal of Sports Medicine and Physical Fitness 23: 52-58, 1983 de Loes M. Medical treatment and costs of sports-related injuries in total population. International Journal of Sports Medicine II: 66-72, 1990 de Loes M, Goldie I. Incidence rate of injuries during sport activity and physical exercise in a rural Swedish municipality: incidence rates in 17 sports. International Journal of Sports Medicine 9: 461-467, 1988 Dickinson J. The training of mobile balancing under a minimal visual cue situation. Ergonomics II: 69-75, 1968 Edwards RHT. Hypotheses of peripheral and central mechanisms underlying occupational muscle pain and injury. European Journal of Applied Physiology 57: 275-281, 1988 Ekstrand J, Gillquist J. The avoidability of soccer injuries. International Journal of Sports Medicine 4: 124-128, 1983a Ekstrand J, Gillquist J. Soccer injuries and their mechanisms: a prospective study. Medicine and Science in Sports and Exercise 15: 267-270, 1983b Ekstrand J, Gillquist J, Liljedahl SO. Prevention of soccer inju-
373
ries: supervision by doctor and physiotherapist. American Journal of Sports Medicine II: 116-120, 1983 Era P, Jokela J, Heikkinen E. Reaction and movement times in men of different ages: a population study. Perceptual and Motor Skills 63: 111-130, 1986 Farrimond T. Effect of alcohol on visual constancy values and possible relation to driving performance. Perceptual and Motor Skills 70: 291-295, 1990 Forth CD, Salmoni AW. Relationships among self-reported physical activity, aerobic fitness and reaction time. Canadian Journal of Sports Sciences 13: 88-90, 1988 Geary DC, Widaman KF. Individual differences in cognitive arithmetic. Journal of Experimental Psychology [General] 116: 154-171, 1987 Grace TG, Skipper BJ, Newberry JC, Nelson MA, Sweetser ER, et al. Prophylactic knee braces and injury to the lower extremity. Journal of Bone and Joint Surgery 70-A: 422-427, 1988 Guilford JP. The nature of human intelligence, McGraw-Hill, London, 1971 Harbin G, Durst L, Harbin D. Evaluation ofoculomotor response in relationship to sports performance. Medicine and Science in Sports and Exercise 21: 258-262, 1989 Hardy CJ, Riehl RE. An examination of the life stress-injury relationship among noncontact sport participants. Behavioral Medicine 14: 113-118, 1988 Heckel RV, Allen SS, Andrews L, Roeder G, Ryba P, et al. Normative data on the Kagan Matching Familiar Figures test for adult male incarcerates. Journal of Clinical Psychology 45: 155160, 1989 Heim AW, Watts KP, Simmons V. AH2/AH3 manual, NFER, Windsor, 1974 Henry FM. Reaction time and movement time correlations. Perceptual and Motor Skills 12: 63-66, 1961 Hick WE. On the rate of gain of information. Quarterly Journal of Experimental Psychology 4: 11-26, 1952 Hilakivi I, Veilahti J, Asplund P, Sinivuo J, Laitinen L, et al. A sixteen-factor personality test for predicting automobile driving accidents of young drivers. Accident Analysis and Prevention 21: 413-418, 1989 Hill RD. Residual effects of cigarette smoking on cognitive performance in normal aging. Psychology and Aging 4: 251-254, 1989 Hindmarch I. Immediate and overnight effects ofzopiclone 7.5mg and nikazepam 5mg with ethanol, on psychomotor performance and memory in healthy volunteers. International Clinical Psychopharmacology 5 (Suppl. 2): 105-113, 1990 Hindmarch I, Harrison C. The effects of paroxetine and other antidepressants in combination with alcohol on psychomotor activity related to car driving. Acta Psychiatrica Scandinavica 350: 45, 1989 Hinkle LE, Wolff HG. Ecologic investigations ofthe relationship between illness, life experiences and the social environment. New England Journal of Medicine 49: 1373-1388, 1958 Hodgkins J. Reaction time and speed of movement in males and females of various ages. Research Quarterly 34: 335-343, 1963 Holmes TH, Rahe RH. The social readjustment rating scale. Journal of Psychosomatic Research 11: 213-218,1967 Home JA, Gibbons H. Effects on vigilance performance and sleepiness of alcohol given in the early afternoon ('post lunch') vs. early evening. Ergonomics 34: 67-77, 1991 Hughes JR, Keenan RM, Yellin A. Effects of tobacco withdrawal on sustained attention: Addictive Behaviors 14: 577-580, 1989 Hulkko A. Stress fractures in athletes, academic dissertation, University of Oulu, Oulu, 1988 Inkelis SH, Stroberg AJ, Keller EL, Christenson PD. Roller skating injuries in children. Pediatric Emergency Care 4: 127-132, 1988 Jackson OW, Jarrett H, Bailey 0, Kausek J, Swanson J, et al.
374
Injury prediction in the young athlete: a preliminary report. American Journal of Sports Medicine 6: 6-14, 1978 James SL, Bates BT, Osternig LR. Injuries to runners. American Journal of Sports Medicine 6: 40-50, 1978 Jensen AR, Munro E. Reaction time, movement time and intelligence. Intelligence 3: 121-126, 1979 Jensen AR, Vernon PA. Jensen's reaction-time studies: a reply to Longstreth. Intelligence 10: 153-179, 1986 Jordan T'C, Characteristics of visual and proprioceptive response times in the learning of a motor skill. Quarterly Journal of Experimental Psychology 24: 536-543, 1972 Kamen G, Morris HH. Differences in sensorimotor processing of visual and proprioceptive stimuli. Research Quarterly 59: 2934, 1988 Kelley MJ. Psychological risk factors and sports injuries. Journal of Sports Medicine and Physical Fitness 30: 202-221, 1990 Kerr G, Fowler B. The relationship between psychological factors and sports injuries. Sports Medicine 6: 127-134, 1988 Kerr G, Minden H. Psychosocial factors related to the occurrence of athletic injuries. Journal of Sport and Exercise Psychology 10: 167-173, 1988 Kilburn KH, Warshaw R, Thornton JC, Husmark I. An examination of factors that could affect choice reaction time in histology technicians. American Journal of Industrial Medicine 15: 679-686, 1989 Klein RM, Posner MI. Attention to visual and kinaesthetic components of skills. Brain Research 71 : 401-411, 1974 Kuitunen T, Mattila MJ, Seppala T. Actions and interactions of hypnotics on human performance: single doses of zopiclone, triazolam and alcohol. International Clinical Psychopharmacology 5 (Suppl. 2): 115-130, 1990 Kujala UM. Knee exertion injuries in adolescents and young adults: a study with special reference to anatomic predisposition, Publications of the Social Insurance Institution, Finland, Turku, 1986 Kujala UM, Heinonen OJ, Lehto M, Jarvinen M, Bergfeld JA. Equipment, drugs and problems of the competition and team physician. Sports Medicine 6: 197-209, 1988 Lattila R, Heiskanen T, Komulainen R, Niskanen T, Siren R. Tapaturmat ja vakivalta 1980 (accidents and violence 1980), Central Statistical Office of Finland, Helsinki, 1982 Lindley RH, Smith WR, Thomas TJ. The relationship between speed of information processing as measured by timed paperand-pencil tests and psychometric intelligence. Intelligence 12: 17-25, 1988 Lindqvist KS. Epidemiology of accidents in a Swedish municipality. Accident Analysis and Prevention 21: 33-43, 1989 Logan GO. On the use of a concurrent memory load to measure attention and automaticity. Journal of Experimental Psychology - Human Perception and Performance 5: 189-207, 1979 Lysens R, Stevernlynck A, van den Auweele Y, Lefevre J, Renson L, et al. The predictability of sports injuries. Sports Medicine I: 6-10, 1984 Lysens R, van den Auweele Y, Ostyn M. The relationship between psychosocial factors and sports injuries. Journal of Sports Medicine and Physical Fitness 26: 77-84, 1986 Lysens R, Ostyn MS, vanden Auweele Y, Lefevre J, Vuylsteke M, et al. The accident-prone and overuse-prone profiles of the young athlete. American Journal of Sports Medicine 17: 612619, 1989 Marteniuk ltG. Information processing in motor skills, Holt, Rinehart and Winston, New York, 1976 Martens CH, Ross LE, Mundt Je. Young drivers' evaluation of driving impairment due to alcohol. Accident Analysis and Prevention 23: 67-76, 1991 Matthews G, Oorn L. IQ and choice reaction time: an information processing analysis. Intelligence 13: 299-317, 1989 Mattila MJ, Mattila ME. Effects of remoxipride on psychomotor
Sports Medicine 14 (6) 1992
performance, alone and in combination with ethanol and diazepam. Acta Psychiatrica Scandinavica 358: 54-55, 1990 Maylor EA, Rabbitt PM, Connolly SA. Rate of processing and judgment of response speed: comparing the effects of alcohol and practice. Perception and Psychophysics 45: 431-438, 1989 McKenzie DC, Clement DB, Taunton JE. Running shoes, orthotics and injuries. Sports Medicine 2: 334-347, 1985 Mero A, Jaakkola L, Komi PV. Neuromuscular, metabolic and hormonal profiles of young tennis players and untrained boys. Journal of Sports Sciences 7: 95-100, 1989 Mongrain S, Standing L. Impairment of cognition, risk-taking, and self-perception by alcohol. Perceptual and Motor Skills 69: 199-210, 1989 Neubauer Ae. Selective reaction times and intelligence. Intelligence 14: 79-96, 1990 O'Toole BI. Intelligence and behaviour and motor vehicle accident mortality. Accident Analysis and Prevention 22: 211-221, 1990 Passer MW, Seese MD. Life stress and athletic injury: examination of positive versus negative events and three moderator variables. Journal of Human Stress 9: 11-16, 1983 Persaud G, Salmon HM. Factor structure of newly designed verbal tests. Perceptual and Motor Skills 67: 123-128, 1988 Rabbitt P, Banerji N. How does very prolonged practice improve decision speed? Journal of Experimental Psychology [General] 118: 338-345, 1989 Raffle PA. Interrelation between alcohol and accidents. Journal of the Royal Society of Health 82: 132-135, 1989 Raven Je. Advanced Progressive Matrices: sets I and 2, Lewis & Co, London, 1965 Robey JM, Blyth CS, Mueller Fa. Athletic injuries: application of epidemiologic methods. Journal of American Medical Association 217: 184-189, 1971 Saari J, Tech 0, Lahtela J. Work conditions and accidents in three industries. Scandinavian Journal of Work, Environment and Health 7 (Suppl. 4): 97-105, 1981 Sandelin J, Santavirta S, Lattila R, Vuolle P, Sarna S. Sport injuries in a large urban population: occurrence and epidemiologic aspects. International Journal of Sports Medicine 8: 6166, 1987 Sanders AF. Towards a model of stress and human performance. Acta Physiologica 53: 61-97, 1983 Schmidt RA. Motor control and learning: a behavioral emphasis, Human Kinetics Publishers, Champaign, 1988 Sedgwick AW, Smith OS, Davies MJ. Musculoskeletal status of men and women who entered a fitness programme. Medical Journal of Australia 148: 385-399, 1988 Slack WV, Leviton A, Bennett SE, Fleischmann KH, Lawrence RS. Relation between age, education, and time to respond to questions in a computer-based medical interview. Computers and Biomechanical Research 21: 78-84, 1988 Smith GA. Models of reaction time. In Welford (Ed.) Reaction times, pp. 173-214, Academic Press, London, 1980 Smith SM, Goodman RA, Thacker SB, Burton AH, Parsons JE, et al. Alcohol and fatal injuries: temporal patterns. American Journal of Preventive Medicine 5: 296-302, 1989 Snyder FR, Henningfield JE. Effects of nicotine administration following 12h of tobacco deprivation: assessment on computerized performance tasks. Psychopharmacology 97: 17-22, 1989 Stelmach GE, Goggin NL, Garcia-Corea A. Movement specification time with age. Experimental Aging Research 13: 39-46, 1987 Taerk GS. The injury-prone athlete: a psychosocial approach. Journal of Sports Medicine and Physical Fitness 17: 187-194, 1977 Taimela S. Relation between speed of reaction and psychometric tests of mental ability in musculoskeletal injury-prone subjects. Perceptual and Motor Skills 70: 155-161, 1990
Information Processing and Accidental Injuries
Taimela S. Choice reaction time, intelligence and accidental injuries. Submitted, 1992 Taimela S. Factors affecting reaction time testing and the interpretation of the results. Perceptual Motor Skills 73: 1195-2002, 1991 Taimela S, Kujala UM, Osterman K. Intrinsic risk factors and athletic injuries. Sports Medicine 9: 205-215, 1990a Taimela S, Osterman K, Kujala UM, Lehto M, Korhonen T, et al. Motor ability and personality with reference to soccer injuries. Journal of Sports Medicine and Physical Fitness 30: 194201, 1990b Taimela S, Kujala UM, Osterman K. The relation of low grade mental ability to fractures in young men. International Orthopaedics 15: 75-77, 1991a Taimela S, Osterman K, Alaranta H, Soukka A, Kujala UM. Long psychomotor reaction time in patients with chronic low-back pain - a preliminary report. Archives of Physical Medicine and Rehabilitation, in press, 1992 Tomporowski PO, Simpson RG. Sustained attention and intelligence. Intelligence 14: 31-42, 1990 Torg JS, Vegso JJ, Sennelt B, Das M. The national football head and neck injury registry. Journal of the American Medical Association 254: 3439-3443, 1985 Ungerholm S, Gustafsson J. Skiing safety in children: a prospective study of downhill skiing injuries and their relation to the
375
skier and his equipment. International Journal of Sports Medicine 6: 353-358, 1985 Valliant PM. Personality and injury in competitive runners. Perceptual and Motor Skills 53: 251-253, 1981 Van Mechelen W, Hlobil H, Kemper HCG. How can sport injuries be prevented? National Institute for Sports Health Care, Oosterbeek, The Netherlands, 1987 Watson AWS. Sports injuries during one academic year in 6799 Irish school children. American Journal of Sports Medicine 12: 65-71, 1984 Wechsler D. The measurement and appraisal of adult intelligence, Williams and Wilkins, Baltimore, 1958 Welford AT. Choice reaction time: basic concepts. In Welford (Ed.) Reaction times, pp. 73-128, Academic Press, London, 1980a Welford AT. Relationships between reaction time and fatigue, stress, age and sex. In Welford (Ed.) Reaction times, pp. 321354, Academic Press, London, 1980b Widaman KF, Carlson JS. Procedural effects of performance on the Hick paradigm: bias in reaction time and movement time parameters. Intelligence 13: 63-85, 1989 Correspondence and reprints: Dr Sima Taimela, Helsinki Research Institute for Sports and Exercise Medicine, Toolan Kisahalli, Mannerheimintie 17, SF-00250, Helsinki, Finland.
