Perceptualand Motor Skills, 1992, 74, 151-157. O Perceptual and Motor Skills 1992
EFFECT O F CAFFEINE O N MOTOR PERFORMANCE BY CAFFEINE-NAIVE AND -FAMILIAR SUBJECTS ' B. H. JACOBSON AND S. R. THURMAN-LACEY
Oklahoma State Uniuenio Summary.-The purpose of this investigation was to assess the effect of caffeine on selected manipulation skills by caffeine-naive and caffeine-fadar subjects. The subjects were 20 caffeine-naive ( < 9 0 mg/d) and 20 caffeine-familiar ( >750 mg/d) collegeage (21 1.7 yr) women. Measurements included steadiness error time and frequency, duration of tracing, error time and frequency, and dexterity. Doses of 2.5, 5.0 mg.kg-' body weight caffeine or a placebo (200 mg. methylcellulose) were administered randomly to all subjects on three separate occasions. A 2 x 3 repeated-measures analysis of variance yielded a significant group difference for steadiness error time between the 5 rng.kg-' and 2.5 mg.kg-' dose and between 5 mg9kg-' and the placebo. For frequency of steadiness .errors, the nonuser group posted significant gains for both 5.0 and 2.5 rng.kg-' over the placebo control. On tracing error time and error frequency, 5.0 mg.kg-' resulted in significant increases from both 2.5 mg.kg-' and the placebo group. In the caffeine-naive group, both doses of caffeine led to significant increases in dexterity time from the placebo, and the 5.0 mg.kg-' dose was significantly different from the 2.5 rng,kg-' trial. It was concluded that caffeine had detrimental effects on selected performance skills of caffeine-naive women but not in caffeine-familiar women.
*
The effect of ingested caffeine on physical performance has been a topic of recent interest. Contemporary researchers have investigated the relationship between caffeine ingestion and gross motor activity such as endurance (Costill, Dalsky, & Fink, 1978; Ivy,, CostiU, Fink, & Lower, 1979), strength (Jacobson & Edwards, 19911, and speed (Jacobson & Edgley, 1987). With respect to fine motor activity, claims of impaired coordination and hand steadiness as a result of caffeine ingestion have been reported. Of the few existing studies, equivocal results have been found with respect to caffeine's effect on motor performance. Many of the early studies were plagued with poor designs and obsolete measurements (Williams, 1983; Van Handle, 1983). Further criticism, of previous studies focuses cn the possibility of caffeine desensitization due to habitual use of caffeine by the subjects (Robertson, Wade, Workman, Woosley, & Oats, 1981; Colton, Gosswlin, & Smith, 1968). Hence, tolerance built on recent or chronic use of caffeine may yield data different from those collected from a caffeine-naive population. As an ingredient in numerous beverages, foods, and proprietary drugs, caffeine is currently considered the most wide-spread and indiscriminately 'Request reprints from Dr. B. H. Jacobson, Coordinator of Graduate Studies and Research, School of Health, Physical Education and Leisure, Oklahoma State University, StiUwater, OK 74078.
152
B. H. JACOBSON & S. R. THURMAN-LACEY
used drug (Jacobson & KuJling, 1989). According to contemporary figures, the use of caffeine in the work environment exceeds 350 mg/d (Jacobson & Bouher, 1991). The abundant and chronic use of caffeine combined with work-related duties dependent on steady hands and manipulative skills may jeopardize performance, result in poor quality of work, or place the worker in danger. Peak blood plasma concentrations occur 30 to 60 minutes following ingestion of caffeine (Beach, Bianchine, & Gerber, 1984). The drug directly affects the vagal, medullary, and vasomotor centers (Syed, 1976) and alters the formation and release of neurotransmitters (Fernstrom & Fernstrorn, 1984). Following ingestion, high caffeine concentrations are prominent in all muscle tissue (Burg, 1975) which subsequently alters calcium permeability and utilization (Kavaler, Anderson, & Fisher, 1978). Caffeine also affects contractile status and patterns of fiber recruitment (Van Handle, 1983). Very early studies reported that the consumption of caffeine yielded unsteadiness of hands (Hollingsworth, 1912) and increased hand tremor (Hull, 1935; Lehmann & Csank, 1957). Given the lack of adequate statistical analysis, one can only speculate to what extent these manifestations may have occurred. Another study (Seashore & Ivy, 1953) found no effect on steadiness as a result of caffeine ingestion. A more recent study (Gemmell & Jacobson, 1990) gave no significant differences in hand steadiness between groups ingesting one of two separate doses of caffeine or a placebo. However, following a power analysis of the data, the authors acknowledged that additional subjects were needed to predict the caffeine effect accurately. Two separate studies found that caffeine may (Putz-Anderson, Setzer, & Croxton, 1981) or may not (Goldstein, Kaizer, & Warren, 1965) affect coordination. Other investigations have shown that motor performance was not affected by consumption of caffeine (Lieberman, Wurtman, Emde, Roberts, & Coviella, 1987) and motor times significantly improved following caffeine consumption (Smith, Tong, & Leigh, 1977). However, the latter authors stated that caffeine had deleterious effects on hand steadiness. Our most recent study (Jacobson, Winter-Roberts, & Gemmell, 1991) showed significant impairment of hand steadiness and coordination following 2 . 5 and 5.0 milligrams per kilogram body-weight of caffeine (mg.kg-'). Differences in protocol, dose administration, tolerance, and caffeine quantity may have accounted for the equivocal results found in previous literature. Surveys related to caffeine consumption have noted increased tremulousness in men consuming an average of 258 mg/d over those consuming 237 mg/d, and for women consuming 272 mg/d over those consuming 231 mg/d (Shirlow & Mathers, 1985). Conversely, one study (Koller, Cone, & Herbster, 1987) indicated that only two percent of subjects consuming an average of 325 mg/day noted shaky hands. These authors concluded that caffeine infrequently induces tremor.
CAFFEINE AND MOTOR PERFORMANCE
153
I t was the purpose of this study to examine and compare the effect of caffeine on hand steadiness, coordination, and manual dexterity in caffeine-naive and caffeine-familiar subjects.
Subjects
Forty college-age women (M: 21.0, SD:2.1 yr.) whose mean weight was 58.2 kg (SD:2.9 kg) volunteered to participate. As stipulated by the guidelines of the university review board, subjects were assured confidentiality and were required to consent in writing prior to participation in the study. All subjects completed a medical history questionnaire and a caffeine consumption questionnaire which included all common sources of caffeine. Also, subjects were screened for caffeine use by recording caffeine intake from all sources over a consecutive 5-day period. Using the responses from their caffeine consumption questionnaires and dietary records, 20 subjects were labeled as caffeine-naive ( < 9 0 mg.d-') and 20 labeled as caffeine-familiar (> 750 mg.d-I). Caffeine-naive subjects were instructed to avoid all products containing caffeine for four days prior to each testing session to reduce any residual caffeine tolerance which may have interfered with test results (Fisher, McMurray, Berry, Mar, & Forsythe, 1986). The caffeine users were instructed to continue their daily consumption of caffeine throughout the duration of the experiment. All subjects reported for testing eight hours postprandial and were questioned about sleep loss, stress level, hang-over, premenstrual symptoms, or any other variable that may have interfered with testing. Rescheduling was allowed if any of these symptoms were evident. Data were collected using three separate instruments. Hand steadiness error time and frequency was measured using a Lafayette Model 32001 Steadiness Tester (hole/stylus type) interfaced with an automatic timer and counter. Total tracing time, error time, and error frequency were measured using a tracing pattern (2 mm wide) mounted on a metal plate interfaced with an automatic timer and counter. Dexterity time was measured using a Lafayette Model 32022 O'Connor Dexterity Test. Hand-steadiness data were obtained by recording the time and frequency of contact with the metal sides of the structure for three 60-sec. trials. For tracing, total tracing time was recorded from beginning to completion of the task, and error time and frequency recorded for three trials. Dexterity was recorded (sec.) from start to end of the predetermined pin-placement task for three trials. The trials for each test were subsequently averaged.
B. H. JACOBSON & S. R. THURMAN-LACEY
154
Drug Administration Experimental caffeine doses (2.5 and 5 . 0 mg.kg-') were administered to
all subjects according to their respective body weights (mg.kg-'). Caffeine doses, as well as the placebo (200 mg methylcellulose), were placed in individualized gelatine capsules and coded by numbers. Following the pretest, doses were administered in combination with 100 ml distdled water. At each of the three testing sessions, one of the three doses (2.5, 5.0 mg.kg", or placebo) were given to the subjects using a double-blind, random counterbalanced design.
Procedure The three testing sessions were conducted at the same time and day each week for a three-week period in a quiet, isolated room to avoid external interference. To avoid an order effect, testing sequence was established with a random design, and subjects were given verbal instructions for each task. Following pretests the subjects were given one of three doses (2.5 mg.kg-', 5 mg.kg-I, or placebo) and asked to sit quietly and read for one full hour to facilitate caffeine absorption (Rall, 1980; Robertson, et a]., 1981). Posttesting followed random station assignments to reduce the .training effect. Identical testing protocols were followed for all groups at least one hour after dose ingestion.
RESULTS The caffeine-naive subjects noted complete compliance with the instructions to avoid all caffeine for a period of four days and the members of both groups verified that they had not eaten eight hours prior to testing sessions. A 2 x 3 repeated-measures analysis of variance was performed for all of the dependent variables with the three doses (2.5 mg.kg-', 5.0 mg-kg-', and placebo) serving as the grouping factor and the two levels (pretest and posttest) serving as the trial factor. The Newman-Keuls (Winer, 1971) post hoc analysis yielded a significant difference ( p ~ 0 . 0 5 )for the caffeine-naive group on hand-steadiness error time between the 5 mg.kg-' trial and the 2.5 mg.kg" trial and between the 5 mg.kg-' trial and placebo trials (Table 1). No significant change was found for the caffeine-familiar group. For hand-steadiness error frequency, the caffeine-naive group posted significant gains ( p c 0 . 0 5 ) between the 5.0 mg.kg-' trial and the placebo trial and between the 2.5 mg.kg-' trial and the placebo trial (Table 1). No significant 'changes in hand-steadiness error frequency occurred in the caffeinefamiliar group. For tracing, no significant changes in total time were seen in either of the groups. However, the caffeine-naive group posted significant differences between the 5.0 mg.kg-' dose and the placebo groups and between the 5.0 mg.kg-' dose and the 2.5 mg.kg-' dose for both tracing error and time (Table 1).
155
CAFFEINE AND MOTOR PERFORMANCE
TABLE 1 PRE-AND POSTTESTMEANS AND STANDARD DEVIATIONSFORDEPENDENT VARLABLES Measures
Caffeine Naive (n = 20) Pretest Posttest M SD M SD
Hand Steadiness Error Time (sec.) Placebo 4.3 3.1 2.5 mg 5.5 2.3 5.9 4.2 5.0 mg Hand Steadiness Error Frequency 57.1 29.3 Placebo 2 5 mg 68.5 25.9 3 1 5 0 mg 66.8 Total Trac~ngTime (sec.) Placebo 24.4 11.2 14.3 25.6 2.5 rng 29.1 15.3 5.0 mg Tracing Error Time (sec.) 2.2 Placebo 4.1 1.9 2.5 rng 3.9 3.1 4.3 5.0 rug Tracing Error Frequency 7.4 21.6 Placebo 2.5 mg 20.9 5.1 10.7 21.8 5.0 mg Dexterity Time (scc ) Placebo 984 17.7 936 14.0 2.5 mg 13.9 107.7 5.0 rng
3.gb 7.3" 10.7'~
Caffeine Familiar (n = 20) Pretest Posttest
M
SD
M
SD
2.2 3.2 5.1
6.2 5.0 4.9
3.7 2.4 2.1
6.0 5.4 7.4
6.5 2.9 2.6
51.7~' 20.9 91.6' 21.9 105.2~ 44.3
73.5 61.6 70.6
30.4 28.5 20.6
66.5 78.1 101.8
39.4 33.9 41.0
14.1 15.4 16.2
33.4 22.3 351
13.5 22.2 23.3
31.5 20.5 30.3
15.4 11.3 13.0
2.3 1.7 4.6
4.6 3.7 4.5
3.8 2.9 1.5
4.1 3.6 5.1
3.1 2.4 1.8
2 ~ . 4 ~ 7.1 23.6V.5 33.60~ 13.7
19.1 18.8 22.1
8.7 5.9 5.4
18.1 21.6 23.7
6.3 7.1 3.2
107.2 114.1 116.9
19.5 12.3 17.1
99.0 109.9 113.7
13.8 18.5 18.8
24.0 28.0 30.4 3.9b 4.3' 7.2"
94.6b 102.3' 118.9"
12.4 13.7 19.2
"bcp < 0:05.
For the dexterity test,' the 5.0 mg.kg-' trial registered significant (p
EFFECT O F CAFFEINE O N MOTOR PERFORMANCE BY CAFFEINE-NAIVE AND -FAMILIAR SUBJECTS ' B. H. JACOBSON AND S. R. THURMAN-LACEY
Oklahoma State Uniuenio Summary.-The purpose of this investigation was to assess the effect of caffeine on selected manipulation skills by caffeine-naive and caffeine-fadar subjects. The subjects were 20 caffeine-naive ( < 9 0 mg/d) and 20 caffeine-familiar ( >750 mg/d) collegeage (21 1.7 yr) women. Measurements included steadiness error time and frequency, duration of tracing, error time and frequency, and dexterity. Doses of 2.5, 5.0 mg.kg-' body weight caffeine or a placebo (200 mg. methylcellulose) were administered randomly to all subjects on three separate occasions. A 2 x 3 repeated-measures analysis of variance yielded a significant group difference for steadiness error time between the 5 rng.kg-' and 2.5 mg.kg-' dose and between 5 mg9kg-' and the placebo. For frequency of steadiness .errors, the nonuser group posted significant gains for both 5.0 and 2.5 rng.kg-' over the placebo control. On tracing error time and error frequency, 5.0 mg.kg-' resulted in significant increases from both 2.5 mg.kg-' and the placebo group. In the caffeine-naive group, both doses of caffeine led to significant increases in dexterity time from the placebo, and the 5.0 mg.kg-' dose was significantly different from the 2.5 rng,kg-' trial. It was concluded that caffeine had detrimental effects on selected performance skills of caffeine-naive women but not in caffeine-familiar women.
*
The effect of ingested caffeine on physical performance has been a topic of recent interest. Contemporary researchers have investigated the relationship between caffeine ingestion and gross motor activity such as endurance (Costill, Dalsky, & Fink, 1978; Ivy,, CostiU, Fink, & Lower, 1979), strength (Jacobson & Edwards, 19911, and speed (Jacobson & Edgley, 1987). With respect to fine motor activity, claims of impaired coordination and hand steadiness as a result of caffeine ingestion have been reported. Of the few existing studies, equivocal results have been found with respect to caffeine's effect on motor performance. Many of the early studies were plagued with poor designs and obsolete measurements (Williams, 1983; Van Handle, 1983). Further criticism, of previous studies focuses cn the possibility of caffeine desensitization due to habitual use of caffeine by the subjects (Robertson, Wade, Workman, Woosley, & Oats, 1981; Colton, Gosswlin, & Smith, 1968). Hence, tolerance built on recent or chronic use of caffeine may yield data different from those collected from a caffeine-naive population. As an ingredient in numerous beverages, foods, and proprietary drugs, caffeine is currently considered the most wide-spread and indiscriminately 'Request reprints from Dr. B. H. Jacobson, Coordinator of Graduate Studies and Research, School of Health, Physical Education and Leisure, Oklahoma State University, StiUwater, OK 74078.
152
B. H. JACOBSON & S. R. THURMAN-LACEY
used drug (Jacobson & KuJling, 1989). According to contemporary figures, the use of caffeine in the work environment exceeds 350 mg/d (Jacobson & Bouher, 1991). The abundant and chronic use of caffeine combined with work-related duties dependent on steady hands and manipulative skills may jeopardize performance, result in poor quality of work, or place the worker in danger. Peak blood plasma concentrations occur 30 to 60 minutes following ingestion of caffeine (Beach, Bianchine, & Gerber, 1984). The drug directly affects the vagal, medullary, and vasomotor centers (Syed, 1976) and alters the formation and release of neurotransmitters (Fernstrom & Fernstrorn, 1984). Following ingestion, high caffeine concentrations are prominent in all muscle tissue (Burg, 1975) which subsequently alters calcium permeability and utilization (Kavaler, Anderson, & Fisher, 1978). Caffeine also affects contractile status and patterns of fiber recruitment (Van Handle, 1983). Very early studies reported that the consumption of caffeine yielded unsteadiness of hands (Hollingsworth, 1912) and increased hand tremor (Hull, 1935; Lehmann & Csank, 1957). Given the lack of adequate statistical analysis, one can only speculate to what extent these manifestations may have occurred. Another study (Seashore & Ivy, 1953) found no effect on steadiness as a result of caffeine ingestion. A more recent study (Gemmell & Jacobson, 1990) gave no significant differences in hand steadiness between groups ingesting one of two separate doses of caffeine or a placebo. However, following a power analysis of the data, the authors acknowledged that additional subjects were needed to predict the caffeine effect accurately. Two separate studies found that caffeine may (Putz-Anderson, Setzer, & Croxton, 1981) or may not (Goldstein, Kaizer, & Warren, 1965) affect coordination. Other investigations have shown that motor performance was not affected by consumption of caffeine (Lieberman, Wurtman, Emde, Roberts, & Coviella, 1987) and motor times significantly improved following caffeine consumption (Smith, Tong, & Leigh, 1977). However, the latter authors stated that caffeine had deleterious effects on hand steadiness. Our most recent study (Jacobson, Winter-Roberts, & Gemmell, 1991) showed significant impairment of hand steadiness and coordination following 2 . 5 and 5.0 milligrams per kilogram body-weight of caffeine (mg.kg-'). Differences in protocol, dose administration, tolerance, and caffeine quantity may have accounted for the equivocal results found in previous literature. Surveys related to caffeine consumption have noted increased tremulousness in men consuming an average of 258 mg/d over those consuming 237 mg/d, and for women consuming 272 mg/d over those consuming 231 mg/d (Shirlow & Mathers, 1985). Conversely, one study (Koller, Cone, & Herbster, 1987) indicated that only two percent of subjects consuming an average of 325 mg/day noted shaky hands. These authors concluded that caffeine infrequently induces tremor.
CAFFEINE AND MOTOR PERFORMANCE
153
I t was the purpose of this study to examine and compare the effect of caffeine on hand steadiness, coordination, and manual dexterity in caffeine-naive and caffeine-familiar subjects.
Subjects
Forty college-age women (M: 21.0, SD:2.1 yr.) whose mean weight was 58.2 kg (SD:2.9 kg) volunteered to participate. As stipulated by the guidelines of the university review board, subjects were assured confidentiality and were required to consent in writing prior to participation in the study. All subjects completed a medical history questionnaire and a caffeine consumption questionnaire which included all common sources of caffeine. Also, subjects were screened for caffeine use by recording caffeine intake from all sources over a consecutive 5-day period. Using the responses from their caffeine consumption questionnaires and dietary records, 20 subjects were labeled as caffeine-naive ( < 9 0 mg.d-') and 20 labeled as caffeine-familiar (> 750 mg.d-I). Caffeine-naive subjects were instructed to avoid all products containing caffeine for four days prior to each testing session to reduce any residual caffeine tolerance which may have interfered with test results (Fisher, McMurray, Berry, Mar, & Forsythe, 1986). The caffeine users were instructed to continue their daily consumption of caffeine throughout the duration of the experiment. All subjects reported for testing eight hours postprandial and were questioned about sleep loss, stress level, hang-over, premenstrual symptoms, or any other variable that may have interfered with testing. Rescheduling was allowed if any of these symptoms were evident. Data were collected using three separate instruments. Hand steadiness error time and frequency was measured using a Lafayette Model 32001 Steadiness Tester (hole/stylus type) interfaced with an automatic timer and counter. Total tracing time, error time, and error frequency were measured using a tracing pattern (2 mm wide) mounted on a metal plate interfaced with an automatic timer and counter. Dexterity time was measured using a Lafayette Model 32022 O'Connor Dexterity Test. Hand-steadiness data were obtained by recording the time and frequency of contact with the metal sides of the structure for three 60-sec. trials. For tracing, total tracing time was recorded from beginning to completion of the task, and error time and frequency recorded for three trials. Dexterity was recorded (sec.) from start to end of the predetermined pin-placement task for three trials. The trials for each test were subsequently averaged.
B. H. JACOBSON & S. R. THURMAN-LACEY
154
Drug Administration Experimental caffeine doses (2.5 and 5 . 0 mg.kg-') were administered to
all subjects according to their respective body weights (mg.kg-'). Caffeine doses, as well as the placebo (200 mg methylcellulose), were placed in individualized gelatine capsules and coded by numbers. Following the pretest, doses were administered in combination with 100 ml distdled water. At each of the three testing sessions, one of the three doses (2.5, 5.0 mg.kg", or placebo) were given to the subjects using a double-blind, random counterbalanced design.
Procedure The three testing sessions were conducted at the same time and day each week for a three-week period in a quiet, isolated room to avoid external interference. To avoid an order effect, testing sequence was established with a random design, and subjects were given verbal instructions for each task. Following pretests the subjects were given one of three doses (2.5 mg.kg-', 5 mg.kg-I, or placebo) and asked to sit quietly and read for one full hour to facilitate caffeine absorption (Rall, 1980; Robertson, et a]., 1981). Posttesting followed random station assignments to reduce the .training effect. Identical testing protocols were followed for all groups at least one hour after dose ingestion.
RESULTS The caffeine-naive subjects noted complete compliance with the instructions to avoid all caffeine for a period of four days and the members of both groups verified that they had not eaten eight hours prior to testing sessions. A 2 x 3 repeated-measures analysis of variance was performed for all of the dependent variables with the three doses (2.5 mg.kg-', 5.0 mg-kg-', and placebo) serving as the grouping factor and the two levels (pretest and posttest) serving as the trial factor. The Newman-Keuls (Winer, 1971) post hoc analysis yielded a significant difference ( p ~ 0 . 0 5 )for the caffeine-naive group on hand-steadiness error time between the 5 mg.kg-' trial and the 2.5 mg.kg" trial and between the 5 mg.kg-' trial and placebo trials (Table 1). No significant change was found for the caffeine-familiar group. For hand-steadiness error frequency, the caffeine-naive group posted significant gains ( p c 0 . 0 5 ) between the 5.0 mg.kg-' trial and the placebo trial and between the 2.5 mg.kg-' trial and the placebo trial (Table 1). No significant 'changes in hand-steadiness error frequency occurred in the caffeinefamiliar group. For tracing, no significant changes in total time were seen in either of the groups. However, the caffeine-naive group posted significant differences between the 5.0 mg.kg-' dose and the placebo groups and between the 5.0 mg.kg-' dose and the 2.5 mg.kg-' dose for both tracing error and time (Table 1).
155
CAFFEINE AND MOTOR PERFORMANCE
TABLE 1 PRE-AND POSTTESTMEANS AND STANDARD DEVIATIONSFORDEPENDENT VARLABLES Measures
Caffeine Naive (n = 20) Pretest Posttest M SD M SD
Hand Steadiness Error Time (sec.) Placebo 4.3 3.1 2.5 mg 5.5 2.3 5.9 4.2 5.0 mg Hand Steadiness Error Frequency 57.1 29.3 Placebo 2 5 mg 68.5 25.9 3 1 5 0 mg 66.8 Total Trac~ngTime (sec.) Placebo 24.4 11.2 14.3 25.6 2.5 rng 29.1 15.3 5.0 mg Tracing Error Time (sec.) 2.2 Placebo 4.1 1.9 2.5 rng 3.9 3.1 4.3 5.0 rug Tracing Error Frequency 7.4 21.6 Placebo 2.5 mg 20.9 5.1 10.7 21.8 5.0 mg Dexterity Time (scc ) Placebo 984 17.7 936 14.0 2.5 mg 13.9 107.7 5.0 rng
3.gb 7.3" 10.7'~
Caffeine Familiar (n = 20) Pretest Posttest
M
SD
M
SD
2.2 3.2 5.1
6.2 5.0 4.9
3.7 2.4 2.1
6.0 5.4 7.4
6.5 2.9 2.6
51.7~' 20.9 91.6' 21.9 105.2~ 44.3
73.5 61.6 70.6
30.4 28.5 20.6
66.5 78.1 101.8
39.4 33.9 41.0
14.1 15.4 16.2
33.4 22.3 351
13.5 22.2 23.3
31.5 20.5 30.3
15.4 11.3 13.0
2.3 1.7 4.6
4.6 3.7 4.5
3.8 2.9 1.5
4.1 3.6 5.1
3.1 2.4 1.8
2 ~ . 4 ~ 7.1 23.6V.5 33.60~ 13.7
19.1 18.8 22.1
8.7 5.9 5.4
18.1 21.6 23.7
6.3 7.1 3.2
107.2 114.1 116.9
19.5 12.3 17.1
99.0 109.9 113.7
13.8 18.5 18.8
24.0 28.0 30.4 3.9b 4.3' 7.2"
94.6b 102.3' 118.9"
12.4 13.7 19.2
"bcp < 0:05.
For the dexterity test,' the 5.0 mg.kg-' trial registered significant (p
