Sports Medicine 13 (4): 234-244, 1992

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Physiological Adaptations to Velocity-Controlled Resistance Training Gordon J. Bell and Howard A. Wenger Department of Physical Education and Sport Studies, University of Alberta, Edmonton, Alberta and School of Physical Education University of Victoria, Victoria, British Columbia, Canada

Contents 234 235 23"' 23"' 239 239 240 240 240 24 J 24 J

Summary

Summary I. Muscular Performance During Velocity-Controlled Resistance Exercise 2. Velocity-Controlled Training Adaptations 2.1 Peak Torque 2.2 Neuromuscular Adaptations 2.3 Hypertrophy 2.4 Biochemical Changes 2.5 Circuit Velocity-Controlled Resistance Training 2.6 Anaerobic Power 3. Rehabilitat ion Applications 4. Conclusions

The force-velocity characteristics of skeletal muscle are such that maximal force is inversely related to the velocity of shortening. This relationship has been observed using isolated muscle preparations and intact muscle groups (e.g. knee extensors). Isokinetic dynamometry has revealed some specific physiological adaptations to different velocities of training: an increase in torque and power that are greater at or near the velocity of training; a transfer of torque gains to slower and faster angular velocities after intermediate velocity resistance training; increases in maximal oxygen consumption and cardiac output in response to circuit training; increases in anaerobic power output ; changes in skeletal muscle size and changes in myofibrillar ATPase activity; and new applications for rehabilitation of muscular and ligamentous injuries, and post-coronary patients.

Isokinetic muscle contractions are dynamic and velocity-controlled by an external mechanical de-

on equipment that provides resistance to the movement while attempting to control velocity by

v ice (Thistle et al. 1967). The nature of isokinetic

matching the force generated by the activated

exercise has been reviewed by Watkins and Harris (1983), Osternig (1986), Knuttgen and Kraemer (1987), and Baltzopoulos and Brodie (1989). Velocity-controlled resistance exercise is performed

muscle group(s). Furthermore, no external load, such as free weights, is placed on the individual. Isokinetic dynamometers (e.g. 'Cybex II', 'KinKom') have been designed for this type of exercise

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Velocity-Controlled Resistance Exercise

and the reliability, validity and the inherent problems associated with these type of machines, such as torque overshoot and gravity compensation effects, have been evaluated but not necessarily solved (Bemden et al. 1988;Farrel & Richards 1986; Sapega et al. 1982; Seger et al. 1988; Tredinick & Duncan 1988; Winter et al. 1981). Other devices such as 'Hydra-Fitness Omnitron' provide accommodating resistance to movement through a system of hydraulic cylinders but do not precisely control the velocity of limb movement and are therefore not true isokinetic devices. 'Omnitron' has been shown to be reliable and valid in the measurement of muscular performance (Guffey & Guffey 1989; Legasse et al. 1989). However, caution has been advised when attempting to correlate data from one isokinetic device to another (Thompson et al. 1989). Resistance training at different velocities oflimb movements has resulted in strength gains that were either specific to the velocity of training or have shown a transfer of strength gains to other contraction velocities (Bell et al. 1989; Caiozzo et al. 1981; Coyle et al. 1981; Lesmes et al. 1978; Timm 1987). Benefits other than strength increases have also been observed after velocity-controlled resistance training performed in a circuit. These include increases in maximal oxygen consumption, maximum cardiac output, submaximal exercise responses, myofibrillar ATPase activity and anaerobic power (Bell et al. 1989a,b; Haennal et al. 1989; Petersen et al. 1989). The purpose of this review is to describe the specific and/or nonspecific strength adaptations from voluntary (as opposed to functional electrical stimulation) velocity-controlled resistance training and highlight some additional physiological benefits from this type of training. For purposes of this review, velocity-controlled resistance training will be defined as training using equipment that provides resistance to the application of a force while attempting to control the velocity of movement throughout a range of motion. This definition permits us to combine the results from training on traditional isokinetic dynamometers (e.g. 'Cybex') with other systems such as hydraulic exercise equipment (e.g, 'Hydra-Fit-

ness'). Some of the data presented have been pooled from several sources and do not allow statistical relationships to be determined. Thus, the data presented in figure 2 are used to reflect trends in the physiological adaptations in response to velocitycontrolled resistance training and no statistical comparisons were made. Furthermore, an attempt was made to limit the data presented to adaptations of the knee extensors.

1. Muscular Performance During Velocity-Controlled Resistance Exercise Muscular strength has been defined as the amount of force or tension a muscle or muscle group exerts against a resistance at a specified velocity during a maximal voluntary contraction (Knuttgen & Kraemer 1987). This definition encompasses, but is not limited to, strength assessed as peak torque measured on an isokinetic dynamometer. A complete explanation of muscle contraction types can be found elsewhere (Hislop & Perrine 1967; Knuttgen & Kraemer 1987). An important goal of resistance training is to increase the force generation by skeletal muscle. This can be accomplished through various types of resistance exercises designed to overload the involved muscle groups. Sale and MacDougall (1981) suggested that resistance exercise can be specific to movement patterns, velocity of movement, and/or muscular contraction type and force. Velocity-controlled resistance training equipment attempts to control movement velocity, simulate movement patterns found in various sports, and allows maximal muscle contractions throughout the entire range of limb movement (Hislop & Perrine 1967; Watkins & Harris 1983). A limitation to this type of equipment is the absence of an eccentric component to the muscular contraction (with the exception of some devices such as the 'Kin-Com Isokinetic Dynamometer'). Although it has been suggested that the contribution of eccentric muscle contractions to various sport movements, such as rowing, are minimal (Martindale & Robertson 1984), concentric resistance training enhances eccentric strength (Komi & Buskirk 1972; Pavone &

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Moffat 1985; Petersen et al. 1991). Velocity-controlled resistance training can be considered an effective means to promote gains in strength at particular joint angles. The force-velocity characteristics of skeletal muscle dictate that maximal tension is developed at slow velocities and decreases as the speed of contraction increases. There is some evidence that suggests voluntary torque may be somewhat depressed during slow velocity contractions (Thomas et al. 1987; Wickiewicz et al. 1984). The in vitro force-velocity relationship of isolated skeletal muscle using animal preparations exhibits the greatest tension at zero velocity (isometric) with declining tension as velocity of muscle shortening increases for concentric muscle contractions (Fenn & Marsh 1935; Hill 1938, 1970; Wilke 1950). It has been stated that, in human subjects, torque should be expressed at a specific joint angle (angle-specific torque) and therefore, a somewhat specific muscle length when making comparisons to the in vitro condition (Caiozzo et al. 1981; Perrine & Edgerton 1978). This is in contrast to measuring the highest torque (peak torque) regardless of joint angle. Perrine and Edgerton (1978) have shown that the human in vivo torque-velocity curve for voluntary knee extension (angle-specifictorque) deviated from the in vitro curve and exhibited a plateau in torque followed by a slight decrease after 1.68 rad/sec (96°/ sec). This was supported for knee flexor and plantar flexor muscle groups but not the dorsiflexors (Wickiewicz et al. 1984) and elbow flexors (Rodgers & Berger 1974). However, others (Bell et al. 1989; Thorstensson 1976, 1977), found that knee extension peak torque is greatest at slow angular velocities and continuously declines with increasing angular velocities and therefore, follows more closely the in vitro force-velocity curve as predicted by Hill (1970) than the data presented by others (Osternig et al. 1983; Perrine & Edgerton 1978; Wickiewicz et al. 1984). The controversy may be partly explained by a tension-restricting neural inhibition of the human subjects or by the testing protocol (Hortobagyi & Katch 1990). The presence of a neural tension-limiting mechanism has not been proven but, if it exists, it may be more evi-

Sports Medicine 13 (4) 1992

dent in untrained subjects or in differentially trained athletes, such as endurance-trained vs power-trained (Taylor et al. 1991). Perrine & Edgerton (1978) data suggest that this may be the case as 'approximately one-third' of their subjects with greater strength (see fig. 4, Perrine & Edgerton 1978) showed a continuous increase in angle-specific torque as angular velocity decreased and the highest torque was achieved during the isometric contraction. Recent research suggests that the pattern of the human in vivo torque-velocity curve differs by strength level (Hortobagyi & Katch 1990). The testing protocol undertaken by Perrine and Edgerton (1978) and Caiozzo et al. (1981) involved a graded dynamic knee extension to ensure that the generated torque was maximal at a specified angle (30° below horizontal knee extension), thereby minimising any fatigue during the intitial stages of the contraction and control oscillations within the dynamometer. However, the angle at which maximal force expression occurs during in vivo muscle movements changes with angular velocity, i.e. the joint angle at which the greatest knee extension torque is achieved occurs at a joint angle closer to full knee extension as angular velocity increases in isokinetic exercise (Thorstensson et al. 1976). In addition, many sport movements involve muscle contractions which require maximal efforts at all angles throughout a complete range of motion. Thus, the selection of the joint angle used as a part of the testing protocol for determining angle-specific torque may contribute to the patterning of the human in vivo torque-velocity curve (Hortobagyi & Katch 1990). Therefore, research which defines peak torque as the highest point achieved on the torque vs joint angle curve shows the greatest peak torque at slow angular velocities (Bell et al. 1989b; Coyle et al. 1981; Lesmes et al. 1978). Differences between peak torque and torque at a specific angle are possibly due to differences in strength level or testing protocol, as suggestedby Hortobagyi and Katch (1990). A comparison between peak torque and angle-specific torque measured at a variety of angular velocities (on a 'Cybex II' isokinetic dynamometer) for knee extension in a trained subject is presented

237

Velocity-Controlled Resistance Exercise

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Peak torque

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Angular velocity (rad/sec)

Fig. 1. In vivo torque-velocity curve for knee extension in a trained subject (triathlete). Peak torque was defined as the highest torque obtained regardless of joint angle and anglespecific torque was determined at a joint angle of 65° representing the mean joint angle at which peak torque occurrred for all angular velocities tested.

in figure I. The joint angle was selected based on the mean angle that produced the highest torque during all the velocities tested. Figure I shows a slight depression in the angle-specific torque at the slowest angular velocity tested and during the isometric contraction. However, the difference is minimal and torque was greatest during the isometric contraction and slow angular velocities compared to the fast angular velocities regardless of whether peak torque or angle-specific torque was measured. Other research (Kannus 1991; Kannus et al. 1991) has shown high correlation between angle-specific torque and peak torque measurements and suggests that angle-specific torque offers little further information regarding muscle function than can be obtained from peak torque.

2. Velocity-Controlled Training Adaptations 2.1 Peak Torque The following discussion will deal specifically with training of the human knee extensors unless otherwise stated. Although some controversy still exists regarding the physiological adaptations responsible for the increases or lack of change in peak torque after velocity-controlled resistance training,

some generalisations can be made. Figure 2 displays the relative increases in knee extension torque after training within 3 ranges of angular velocity. Slow angular velocity is defined as ~ 1.75 rad/sec (~ 1000/sec), intermediate as 1.76 to 3.50 rad/sec (101 to 2000/sec), and fast as 3.51 to 5.24 rad/sec (201 to 3000/sec). Slow velocity resistance training has shown knee extension torque and power improvements that are greatest at slow angular velocities but extend to faster angular velocities (Caiozzo et al. 1981; Colliander & Tesch 1990; Kanehisa & Miyashita 1983; Nobbs & Rhodes 1986; Petersen 1988). Some research suggests that increases in torque after slow velocity resistance training are limited to slow and intermediate velocities only (Ewing et al. 1990). Figure 2a represents the relative improvements in torque after slow velocity-controlled resistance training. Since the majority of research utilised a training velocity of 1.05 rad/sec, the greatest relative improvement was evident at this velocity. Intermediate velocity training has produced conflicting results. Some have suggested that the training effect was specific only to the training velocity (3.14 rad/sec) with no transfer to slower velocities (Petersen et al. 1984). However, the majority of research has shown that intermediate velocity resistance training results in a transfer of training effect to slower (Lesmes et al. 1978; Moffroid & Whipple 1990) and both slower and faster angular velocities (Adyanju et al. 1983; Bell et al. 1989a; Kanehisa & Miyashita 1983a; Petersen 1988; Timm 1987). A recent evaluation of the 'spill over' effects of intermediate velocity-controlled resistance training (3.14 rad/sec) showed a magnitude of transfer of at least ± 2.09 rad/sec for both knee extension and knee flexion peak torque (Timm et al. 1987). The relative changes in figure 2b support these latter findings and indicate that intermediate velocity resistance training may produce similar increases in torque at slow and fast angular velocities. Fast velocity-controlled resistance training has also resulted in some controversy in regards to training adaptations. The majority of research has suggested that the gains in torque are more prom-

238

Sports Medicine 13 (4) 1992

Slow Training zone

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0.521.05 1.572.09 2.61 3.14 3.674.194.715.24 Angular velocity (rad/sec)

Fig. 2. (a) The effects of slow velocity-controlled resistance training (~ I. 75 rad/sec) on peak torque at a variety of angular velocities. (b) The effects of intermediate velocity-controlled resistance training (1.76 rad/sec to 3.5 rad/sec resistance training on peak torque at a variety of angular velocities. (c) The effects of fast velocity-controlled resistance training (;;> 3.51 rad/sec) on peak torque at a variety of angular velocities. NA = data not available.

inent at fast angular velocities (Caiozzo et al. 1981; Ewing et al. 1990; Smith & Melton 1981) [see fig. 2c]. On the other hand, Coyle et al. (1981) and Dudley and Djamil (1985) have shown that training at 4.19 rad/sec can produce significant increases in torque which were similar at slow and fast angular velocities. Possible reasons for this finding may include a 'resetting' of a hypothesised tension-limiting mechanism that inhibits maximal force generation because of neural factors (Perrine & Edgerton 1978) or selective development of fast twitch motor units with fast velocity resistance training that would transfer to maximal torque measured at slow angular velocities (Coyle et al. 1981). Thus, the majority of research suggests that maximal gains in torque after training may be somewhat velocity specific, but adaptations of a lesser magnitude do occur outside the specific training velocity. Intermediate velocity-controlled resistance training may be a function of differences in the muscle groups tested. Intermediate velocity training of elbow flexors resulted in greater power increases with light loads while slow velocity resistance training produced significant increases in power with the heaviest loads only (Kanehisa & Miyashita 1983b). Also, the knee flexors have shown greater relative peak torque increases compared to knee extensors after intermediate velocity resistance training (Bell et al. 1988; Lesmes et al. 1978; Petersen et al. 1984). As well, shoulder flexors and extensors showed greater transfer from slow velocity resistance training to intermediate velocity torque and power measures than vice-versa (Garnica 1986) which differs from the transfer pattern in knee extensors and flexors. This indicates that care must be taken in interpreting data using different muscle groups because structural and anatomical differences may affect the observed adaptations. In summary, maximal increases in peak torque predominate at the angular velocity utilised during velocity-controlled resistance training. Some transfer of training can be expected. Considerable transfer of training to both faster and slower velocities may occur with intermediate velocity resistance

239

Velocity-Controlled Resistance Exercise

training and may be preferred for activities requiring a range of movement velocities. 2.2 Neuromuscular Adaptations The adaptations within the nervous system precede the adaptations that occur within muscle during traditional forms of resistance training (Hakkinen & Komi 1983; Moritani & DeVries 1979). The neuromuscular effects are greatest during the first 3 or 4 weeks of resistance training and include: an increase in motor unit excitability; decreases in twitch tension and contraction time; and, an enhanced motor unit synchronisation (Cracraft & Petajan 1977; Milner-Brown et al. 1975; Sale et al. 1982, 1983). These observed neural changes accompanying strength improvements may result from increased activation of prime movers, greater involvement of synergist muscles and/or an inhibition of antagonist muscle groups (Sale 1986, 1987). However, there has been little research that has investigated the neural components of velocity-controlled resistance exercise at different velocities of training. Duchateau and Hainaut (1984) compared isometric to fast dynamic resistance training and found that isometric training produced greater maximal tetanic twitch force and power while dynamic training resulted in greater increases in maximal rate of tetanic twitch tension development and maximal velocity of shortening. These findings imply that the contractile kinetics of muscle may be preferentially adapted with specific velocities of resistance training. Furthermore, it has been hypothesised that a neural tension-limiting mechanism exists within the muscle (muscle spindle) or tendons (Golgi tendon apparatus) and this may be preferentially altered with different resistance training velocities(Perrine & Edgerton 1978). It was suggestedthat low velocity, high resistance training but not high velocity, low resistance training may 'reset' this neural mechanism, which would decrease neural inhibition and enhance force production (Perrine & Edgerton 1978). However, some research has shown that fast angular velocity resistance training produced significant increases in

torque at slow angular velocities that could partially be attributed to a neural adaptation (Coyle et al. 1981; Dudley & DjamiI1985). Westing et al. (1990) have shown that superimposed electrical stimulation does not enhance concentric torque at slow and fast angular velocities. This may suggest that neural mechanisms involved in the inhibition of force such as the Golgi tendon apparatus may be an important consideration in training adaptations. Thus, it seems reasonable to conclude that there is considerable involvement and adaptation of the nervous system with velocity-controlled resistance training. 2.3 Hypertrophy Changes in muscle size with traditional forms of resistance training are well documented, but fewer studies have investigated the role of hypertrophy in velocity-controlled resistance training. Some research has shown increases in fast twitch muscle fibre area with intermediate and high velocity training but nonsignificant changes in slow velocity resistancetraining (Costillet al. 1979; Coyle et al. 1981). Other research has shown increases in types I and IIa fibre area that were similar with slow and fast velocity resistance training (Ewing et al. 1990). It is possible that intermediate to fast velocity resistance training may produce a greater recruitment of fast twitch motor units since the contribution of slow twitch motor units to the generation of force becomes less when contraction time is decreased (Sale 1987). Hypertrophy of whole muscle as determined by computer tomography (CT) scanning of the knee extensors (quadriceps femoris) has shown significant increases in cross sectional area that paralleled increases in peak torque after both slow and intermediate velocitycontrolled resistance training (Bell et al. 1991a;Petersen 1998).These findings are in conflict with the conclusion of Cote et al. (1988) that the increases in functional capacity of muscle after slow velocity-controlled resistance training was unrelated to skeletal muscle fibre hypertrophy. The majority of research seems to show a significant increase in muscle size with velocity-controlled resistance

240

training at a variety of velocities and an increase in muscle cross-sectional area has recently been shown to be positively related to slow, intermediate and fast isokinetic torque (Alway et al. 1990). Therefore, skeletal muscle hypertrophy has been confirmed after velocity-controlled resistance training at a variety of velocities, which is in opposition to the suggestion by Cote et al. (1988) that isokinetic strength training does not appear to induce muscle hypertrophy. 2.4 Biochemical Changes Resistance training derives the majority of energy for exercise from stored adenosine triphosphate (ATP) and the regeneration of ATP from energy released through the breakdown of creatine phosphate and through the breakdown of glycogen/ glucose during glycolysis (MacDougall et al. 1977; Tesch 1987). Concentrations and activities of key enzymes involved in these processes have been shown to increase following traditional resistance training programmes (Costill et al. 1979; MacDougall et al. 1977; Thorstensson et al. 1976). However, other research has failed to show any intramuscular enzyme changes which could be associated with increases in strength even though strength and hypertrophy were evident (Houston et al. 1983; Tesch 1987, 1988). Research investigating the effect of velocity-controlled resistance training on biochemical changes that may influence the expression of muscular force is limited. However, Bell et al. (1991a) have shown a significant increase in myofibrillar ATPase activity after intermediate velocity and slow velocity resistance training (unpublished data). The role of myofibrillar ATPase in force expression has been previously noted (Barany 1967; Belcastro et al. 1981). Thus, biochemical adaptations that contribute to enhanced contraction properties of skeletal muscle may be achieved with velocity-controlled resistance training. 2.5 Circuit Velocity-Controlled Resistance Training Research has shown that a considerable cardiorespiratory load can be achieved during an acute session of exercise on velocity-controlled resistance

Sports Medicine 13 (4) 1992

equipment (Ballor et al. 1987; Katch et al. 1985). Velocity-controlled resistance training performed in a circuit (work: rest ratio of 20 sec: 20 sec) at an intermediate velocity involving a number of upper and lower body exercise stations has been shown to be effective in promoting increases in maximal oxygen consumption (Bell et al. 1988; Petersen et al. 1988), maximal cardiac output and submaximal exercise responses (Haennal et al. 1989; Petersen et al. 1989). Conversely, low velocity resistance training in a circuit (30 sec: 30 sec work: rest ratio) was unable to produce any submaximal or maximal aerobic benefits (Bell et al. 1991b). This was probably the result of the low intensity achieved during the low velocity circuit as evidenced by the low mean training heart rates (approximately 125 beats/min) compared to the higher mean heart rates (approximately 160 beats/min) maintained during intermediate velocity training in a circuit (Bell et al. 1988; Petersen et al. 1989). Thus, a significant aerobic benefit coinciding with enhanced peak torque can occur with intermediate (and probably faster) velocity-controlled resistance training performed in a circuit provided a sufficient intensity is maintained. This same effect may not be apparent with low velocity circuit training as a sufficient aerobic intensity is more difficult to achieve. The relative increases in aerobic fitness (i.e. V02max) are similar to those observed with circuit training using traditional forms of resistance training (Hickson et al. 1980; Stone et al. 1983; Wilmore et al. 1978), but are probably somewhat lower than increases observed after dynamic endurance training. 2.6 Anaerobic Power Anaerobic power output is dependent on both force and velocity by definition: power = (force • distancej/time or force' velocity. By increasing the force and/or velocity of a contraction, an increase in power output should occur. A positive relationship has been shown to exist between peak torque and anaerobic power on a cycle ergometer (Smith 1987) and both slow (Bell et al. 1989a) and intermediate velocity-controlled resistance training (Bell

241

Velocity-Controlled Resistance Exercise

et al. 1989a; Petersen et al. 1984) were effective in promoting increases in anaerobic power output on a cycle ergometer. However, other research has shown that neither slow nor intermediate velocitycontrolled resistance training was able to change power output during an anaerobic rowing test (Bell et al. 1989b) or an anaerobic cycle ergometer test in prepubertal males (Docherty et al. 1987). The inconsistency in velocity or force improvements may be partly due to differences in training programmes, initial fitness levels, age, experience, skill and/or the sensitivity of the anaerobic test in reflecting change. It seems reasonable to conlude that velocity-controlled training contributes to increases in aerobic power, but further research is necessary to support this contention.

3. Rehabilitation Applications Velocity-controlled exercise has been used extensively as a diagnostic and rehabilitation tool (Baltzopoulos & Brodie 1989; Ellenbecker et al. 1988; Grimby et al. 1980; Osternig 1986; Rutherford 1988 ). Maximal torque imbalance between limbs mayor may not be associated with an increased incidence of injury (Grace et al. 1985). However, velocity-controlled resistance exercise has several advantages for various rehabilitation programmes: velocity of limb movement can be controlled; range of joint motion can be limited; no external load is placed on the individual; and, resistance is provided in both directions of limb movement. A central feature is that velocity-controlled resistance exercise involves concentric muscle contractions although eccentric contractions are possible on some machines (e.g. 'KinCom'). Research has shown that maximum voluntary concentric muscle contractions used during exercise on velocity-controlled training equipment result in less muscle soreness and damage than eccentric contractions (Armstrong 1984; Jones et al. 1986; Talag 1973) and are capable of both low resistances and of exercising small muscle groups. These features reduce the risk of muscle and joint strain and injury. Furthermore, fast velocity-controlled resistance training (5.24 rad/sec) has been

shown to be effective in decreasing muscle soreness and facilitating normal muscle performance (Hasson et al. 1989). Finally, cardiovascular stress can be controlled using different work : rest intervals, number of exercises and velocity of contractions, and therefore used as an effective modality for the rehabilitation of post-coronary artery bypass patients (Haennel et al. 1991). Thus, the use of velocity-controlled resistance equipment as a viable modality for rehabilitation can be effective for promoting recovery of muscle function and cardiovascular fitness.

4. Conclusions Velocity-controlled resistance exercise can be used as a viable form of resistance training and has been shown to promote increases in such variables as peak torque, muscle hypertrophy, anaerobic power and some biochemical parameters. It is difficult to compare velocity-controlled resistance training to traditional free weight training programmes due to the differences in mode, training patterns and variables measured. Velocity-controlled resistance training has shown, with a few exceptions, increases in torque that predominate at or near the training velocity. Intermediate velocity resistance training has shown some increases in torque that may 'spill over' to both slow and fast velocities. Other advantages to velocity-controlled resistance training include increases in maximal oxygen consumption, cardiac output and selected submaximal exercise responses. These changes have been observed with intermediate to fast velocities when the exercises were performed in a circuit of several stations to provide sufficient intensity and duration for aerobic training. Finally, velocity-controlled exercise has been used as a diagnostic tool in evaluation of muscle performance and has been successful as a training modality in various rehabilitation programmes. In this respect, velocitycontrolled resistance training has several advantages over traditional free weight resistance training programmes, such as removing the external load

242

on the individual and controlling the range of motion.

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Velocity-Controlled Resistance Exercise

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Sports Medicine 13 (4) 1992

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