CNTF genotype is associated with muscular strength and quality in humans across the adult age span.

The relationship between ciliary neurotrophic factor (CNTF) genotype and muscle strength was examined in 494 healthy men and women across the entire adult age span (20-90 yr). Concentric (Con) and eccentric (Ecc) peak torque were assessed using a Kin-Com isokinetic dynamometer for the knee extensors (KE) and knee flexors (KF) at slow (0.52 rad/s) and faster (3.14 rad/s) velocities. The results were covaried for age, gender, and body mass or fat-free mass (FFM). Individuals heterozygous for the CNTF null (A allele) mutation (G/A) exhibited significantly higher Con peak torque of the KE and KF at 3.14 rad/s than G/G homozygotes when age, gender, and body mass were covaried (P < 0.05). When the dominant leg FFM (estimated muscle mass) was used in place of body mass as a covariate, Con peak torque of the KE at 3.14 rad/s was also significantly greater in the G/A individuals (P < 0.05). In addition, muscle quality of the KE (peak torque at 3.14 rad x s(-1) x leg muscle mass(-1)) was significantly greater in the G/A heterozygotes (P < 0.05). Similar results were seen in a subanalysis of subjects 60 yr and older, as well as in Caucasian subjects. In contrast, A/A homozygotes demonstrated significantly lower Ecc peak torque at 0.52 rad/s for both KE and KF compared with G/G and G/A groups (P < 0.05). No significant relationships were observed at 0.52 rad/s between genotype and Con peak torque. These data indicate that individuals exhibiting the G/A genotype possess significantly greater muscular strength and muscle quality at relatively fast contraction speeds than do G/G individuals. Because of high positive correlations between fast-velocity peak torque and muscular power, these findings suggest that further investigations should address the relationship between CNTF genotype and muscular power.     

Relation between cycling exercise capacity, fiber-type composition, and lower extremity muscle strength and muscle endurance

The aim of the study was to determine the relation between peak oxygen uptake V(O2)peak), peak work rate (WRpeak), fiber-type composition, and lower extremity strength and endurance during a maximal incremental cycle test. Thirty-nine healthy sedentary men, aged 30-46, participated in the study. Subjects performed a maximal incremental cycle test and isokinetic knee extension (KE) and flexion (KF) strength and endurance tests at velocities of 60 and 180° · s(-1). Muscle biopsies were taken from m. vastus lateralis and analyzed for fiber-type composition. A significant correlation existed between KE strength and V(O2)peak and WRpeak. Also, KF endurance correlated significantly to V(O2)peak and WRpeak. The KE endurance correlated significantly to WRpeak (rp = 0.32, p < 0.05) and almost significantly to V(O2)peak (rp = 0.28, p = 0.06). Stepwise multiple regression analyses showed that KE strength, KF endurance, and the percentage of type I fibers could explain up to 40% of the variation in V(O2) and WRpeak. The performance of sedentary subjects in a maximal incremental cycle test is highly affected by knee muscle strength and endurance. Fiber-type composition also contributes but to a smaller extent.     

Effects of age on human muscle torque, velocity, and power in two muscle groups.

The purpose of this study was to test the hypotheses that, under isovelocity conditions, older compared with young humans would 1). be slower to reach target velocity and 2). exhibit a downward shift in the torque-velocity and power-velocity relationships in the ankle dorsiflexor and knee extensor muscles. We studied 12 young (26 +/- 5 yr, 6 men/6 women) and 12 older (72 +/- 6 yr, 6 men/6 women) healthy adults during maximal voluntary concentric contractions at preset target velocities (dorsiflexion: 0-240 degrees /s; knee extension: 0-400 degrees /s) using an isokinetic dynamometer. The time to target velocity was longer in older subjects in the dorsiflexors and knee extensors (both P 相似文献   

Pre-impact lower extremity posture and brake pedal force predict foot and ankle forces during an automobile collision

BACKGROUND: The purpose of this study was to determine how a driver's foot and ankle forces during a frontal vehicle collision depend on initial lower extremity posture and brake pedal force. METHOD OF APPROACH: A 2D musculoskeletal model with seven segments and six right-side muscle groups was used. A simulation of a three-second braking task found 3647 sets of muscle activation levels that resulted in stable braking postures with realistic pedal force. These activation patterns were then used in impact simulations where vehicle deceleration was applied and driver movements and foot and ankle forces were simulated. Peak rearfoot ground reaction force (F(RF)), peak Achilles tendon force (FAT), peak calcaneal force (F(CF)) and peak ankle joint force (F(AJ)) were calculated. RESULTS: Peak forces during the impact simulation were 476 +/- 687 N (F(RF)), 2934 +/- 944 N (F(CF)) and 2449 +/- 918 N (F(AJ)). Many simulations resulted in force levels that could cause fractures. Multivariate quadratic regression determined that the pre-impact brake pedal force (PF), knee angle (KA) and heel distance (HD) explained 72% of the variance in peak FRF, 62% in peak F(CF) and 73% in peak F(AJ). CONCLUSIONS: Foot and ankle forces during a collision depend on initial posture and pedal force. Braking postures with increased knee flexion, while keeping the seat position fixed, are associated with higher foot and ankle forces during a collision.     

Effect of the Fatigue Induced by a 110-km Ultramarathon on Tibial Impact Acceleration and Lower Leg Kinematics

Ultramarathon runners are exposed to a high number of impact shocks and to severe neuromuscular fatigue. Runners may manage mechanical stress and muscle fatigue by changing their running kinematics. Our purposes were to study (i) the effects of a 110-km mountain ultramarathon (MUM) on tibial shock acceleration and lower limb kinematics, and (ii) whether kinematic changes are modulated according to the severity of neuromuscular fatigue. Twenty-three runners participated in the study. Pre- and post-MUM, neuromuscular tests were performed to assess knee extensor (KE) and plantar flexor (PF) central and peripheral fatigue, and a treadmill running bouts was completed during which step frequency, peak acceleration, median frequency and impact frequency content were measured from tibial acceleration, as well as foot-to-treadmill, tibia-to-treadmill, and ankle flexion angles at initial contact, and ankle range of motion using video analysis. Large neuromuscular fatigue, including peripheral changes and deficits in voluntary activation, was observed in KE and PF. MVC decrements of ~35% for KE and of ~28% for PF were noted. Among biomechanical variables, step frequency increased by ~2.7% and the ankle range of motion decreased by ~4.1% post-MUM. Runners adopting a non rearfoot strike pre-MUM adopted a less plantarflexed foot strike pattern post-MUM while those adopting a rearfoot strike pre-MUM tended to adopt a less dorsiflexed foot strike pattern post-MUM. Positive correlations were observed between percent changes in peripheral PF fatigue and the ankle range of motion. Peripheral PF fatigue was also significantly correlated to both percent changes in step frequency and the ankle angle at contact. This study suggests that in a fatigued state, ultratrail runners use compensatory/protective adjustments leading to a flatter foot landing and this is done in a fatigue dose-dependent manner. This strategy may aim at minimizing the overall load applied to the musculoskeletal system, including impact shock and muscle stretch.     

Standing strength training of the ankle plantar and dorsiflexors in older women, using concentric and eccentric contractions

Many studies have reported strength gains in older adults following high-intensity resistance training. However, the muscle contraction types examined have been primarily isometric (static) or concentric (CONC; shortening). Less is known about how eccentric (ECC) strength in older adults responds to training or about the efficacy of ECC contractions as training stimuli in these subjects, even though muscle contractions of this type are performed in most training regimens and daily physical activities. In this study, 15 physically active, healthy older women [68 (5) years; mean (SD)] completed an 8-week resistance training program of two sessions per week. Training consisted of three sets of eight repetitions of CONC ankle plantar flexion (PF) and ECC dorsiflexion (DF), at greater than 80% of the initial peak torque, in a standing position only. Subjects were tested in standing and supine positions for: (1) strength over a range of 10° DF to 20° PF for both CONC and ECC; DF and PF (2) passive resistive torque of the plantar flexors at 6°/s; and (3) DF and PF rate of torque development. All strength testing and training was done at 30°/s. Significant increases (P < 0.01) were found for both CONC DF (↑30%) and ECC DF (↑17%) peak torque in the standing position. No significant changes occurred for DF strength as measured with the subjects in the supine position, PF strength in either position, passive resistive torque, or rate of torque development. In summary, strength gains occurred only in the dorsiflexors, which were trained using ECC contractions. Improvements in DF strength were specific to the position of training, which has implications for the transferability of strength gains to functional tasks such as maintaining gait. Accepted: 17 January 1997     

The role of intersegmental dynamics during rapid limb oscillations

The interactive dynamic effects of muscular, inertial and gravitational moments on rapid, multi-segmented limb oscillations were studied. Using three-segment, rigid-body equations of motion, hip, knee and ankle intersegmental dynamics were calculated for the steady-state cycles of the paw-shake response in adult spinal cats. Hindlimb trajectories were filmed to obtain segmental kinematics, and myopotentials of flexors and extensors at each of the three joints were recorded synchronously with the ciné film. The segmental oscillations that emerged during the paw-shake response were a consequence of an interplay between active and passive musculotendinous forces, inertial forces, and gravity. During steady-state oscillations, the amplitudes of joint excursions, peak angular velocities, and peak angular accelerations increased monotonically and significantly in magnitude from the proximal joint (hip) to the most distal joint (ankle). In contrast to these kinematic relationships, the maximal values of net moments at the hip and knee were equal in magnitude, but of significantly lower magnitude than the large net moment at the ankle joint. At both the ankle and the knee, the flexor and extensor muscle moments were equal, but at the hip the magnitude of the peak flexor muscle moment was significantly greater than the extensor muscle moment. Muscle moments at the hip not only acted to counterbalance accelerations of the more distal segments, but also acted to maintain the postural orientation of the hindlimb. Large muscle moments at the knee functioned to counterbalance the large inertial moments generated by the large angular accelerations of the paw. At the ankle, the muscle moments dominated the generation of the paw accelerations. At the ankle and the knee, muscle moments controlled limb dynamics by slowing and reversing joint motions, and the active muscle forces contributing to ankle and knee moments were derived from lengthening of active musculotendinous units. In contrast to the more distal joints, the active muscles crossing the hip predominantly shortened as a result of the interplay among inertial forces and gravitational moments. The muscle function and kinetic data explain key features of the complex interactions that occur between central control mechanisms and multi-segmented, oscillating limb segments during the paw-shake response.     

Age-related fatigability in knee extensors and knee flexors during dynamic fatiguing contractions

This study investigated the effects of dynamic knee extension and flexion fatiguing task on torque and neuromuscular responses in young and older individuals. Eighteen young (8 males; 25.1 ± 3.2 years) and 17 older (8 males; 69.7 ± 3.7 years) volunteered. Following a maximal voluntary isometric contraction test, participants performed a fatiguing task involving 22 maximal isokinetic (concentric) knee extension and flexion contractions at 60°/s, while surface EMG was recorded simultaneously from the knee extensors (KE) and flexors (KF). Fatigue-induced relative torque reductions were similar between age groups for KE (peak torque decrease: 25.15% vs 26.81%); however, KF torque was less affected in older individuals (young vs older peak torque decrease: 27.6% vs 11.5%; p < 0.001) and this was associated with greater increase in hamstring EMG amplitude (p < 0.001) and hamstrings/quadriceps peak torque ratio (p < 0.01). Furthermore, KE was more fatigable than KF only among older individuals (peak torque decrease: 26.8% vs 11.5%; p < 0.001). These findings showed that the age-related fatigue induced by a dynamic task was greater for the KE, with greater age-related decline in KE compared to KF.     

Individual match playing time during the season affects fitness-related parameters of male professional soccer players

The purpose of this study was to analyze the effects of an entire season on physical fitness parameters (PFPs) in male professional soccer players (N = 18). Performance in 5- and 30-m sprint (T5 and T30), countermovement jump (CMJ), agility (T-test), knee extensor (KE) and knee flexor (KF) isokinetic strength, hamstrings/quadriceps strength ratio (H/Q) and bilateral differences (BDs), and Yo-Yo intermittent endurance test 2 (YYIE2) was evaluated in 4 moments (E1-E4) throughout the season. Individual match playing time was quantified. Significant improvements in CMJ and YYIE2 from E1 to E2 were observed (p < 0.05-0.01). The T30 improved from E2 to E3 (p < 0.01). The CMJ decreased from E2 to E3 and E4, and YYIE2 from E2 to E4 (p < 0.05). There were increments in the H/Q ratio and Agility from E1 and E2 to E3 and E4 (p < 0.05-0.01). Significant correlations were found in all evaluation points between different PFPs and between changes in strength parameters and agility, T5 and T30, CMJ, and YYIE2 (p < 0.05-0.001). Influence of individual match playing time was correlated to changes in T5 (E1 to E3; r = -0.705), KE nondominant leg (KEND; E2 to E3; r = 0.786), and KF (E3 to E4; r = 0.575-0.590). The interrelationship between muscle strength (e.g., KE), sprint (e.g., T5), and jump abilities (CMJ) suggests the importance of muscle strength and power training for soccer. This study suggests that the systematic participation of the players in soccer matches favors the increase and maintenance of soccer players KE and KF muscle strength and sprint ability (T5). Thus, given the unique demands of actual match play, coaches should try to incorporate a competitive friendly match in the weekly training cycle of nonstarter players.     

Mechanical analysis of the landing phase in heel-toe running.

Results of mechanical analyses of running may be helpful in the search for the etiology of running injuries. In this study a mechanical analysis was made of the landing phase of three trained heel-toe runners, running at their preferred speed and style. The body was modeled as a system of seven linked rigid segments, and the positions of markers defining these segments were monitored using 200 Hz video analysis. Information about the ground reaction force vector was collected using a force plate. Segment kinematics were combined with ground reaction force data for calculation of the net intersegmental forces and moments. The vertical component of the ground reaction force vector Fz was found to reach a first peak approximately 25 ms after touch-down. This peak occurs because, in the support leg, the vertical acceleration of the knee joint is not reduced relative to that of the ankle joint by rotation of the lower leg, so that the support leg segments collide with the floor. Rotation of the support upper leg, however, reduces the vertical acceleration of the hip joint relative to that of the knee joint, and thereby plays an important role in limiting the vertical forces during the first 40 ms. Between 40 and 100 ms after touch-down, the vertical forces are mainly limited by rotation of the support lower leg. At the instant that Fz reaches its first peak, net moments about ankle, knee and hip joints of the support leg are virtually zero. The net moment about the knee joint changed from -100 Nm (flexion) at touch-down to +200 Nm (extension) 50 ms after touch-down. These changes are too rapid to be explained by variations in the muscle activation levels and were ascribed to spring-like behavior of pre-activated knee flexor and knee extensor muscles. These results imply that the runners investigated had no opportunity to control the rotations of body segments during the first part of the contact phase, other than by selecting a certain geometry of the body and muscular (co-)activation levels prior to touch-down.     

Propulsion Phase of the Single Leg Triple Hop Test in Women with Patellofemoral Pain Syndrome: A Biomechanical Study

Asymmetry in the alignment of the lower limbs during weight-bearing activities is associated with patellofemoral pain syndrome (PFPS), caused by an increase in patellofemoral (PF) joint stress. High neuromuscular demands are placed on the lower limb during the propulsion phase of the single leg triple hop test (SLTHT), which may influence biomechanical behavior. The aim of the present cross-sectional study was to compare kinematic, kinetic and muscle activity in the trunk and lower limb during propulsion in the SLTHT using women with PFPS and pain free controls. The following measurements were made using 20 women with PFPS and 20 controls during propulsion in the SLTHT: kinematics of the trunk, pelvis, hip, and knee; kinetics of the hip, knee and ankle; and muscle activation of the gluteus maximus (GM), gluteus medius (GMed), biceps femoris (BF) and vastus lateralis (VL). Differences between groups were calculated using three separate sets of multivariate analysis of variance for kinematics, kinetics, and electromyographic data. Women with PFPS exhibited ipsilateral trunk lean; greater trunk flexion; greater contralateral pelvic drop; greater hip adduction and internal rotation; greater ankle pronation; greater internal hip abductor and ankle supinator moments; lower internal hip, knee and ankle extensor moments; and greater GM, GMed, BL, and VL muscle activity. The results of the present study are related to abnormal movement patterns in women with PFPS. We speculated that these findings constitute strategies to control a deficient dynamic alignment of the trunk and lower limb and to avoid PF pain. However, the greater BF and VL activity and the extensor pattern found for the hip, knee, and ankle of women with PFPS may contribute to increased PF stress.     

Viscous properties of human muscle during contraction.

The purpose of this study was to determine viscous properties of human muscle during plantarflexion efforts. Experiments were performed on 17 subjects with an ankle ergometer allowing sinusoidal oscillations during isometric contractions and isokinetic movements. Sinusoidal oscillations led to the expression of (i) Bode diagrams of the musculo-articular system allowing the determination of a damping coefficient (Bbode); and (ii) a viscous coefficient (Bsin) using an adaptation of Hill's equation to sinusoidal oscillations. Isokinetic movements led to torque-velocity relationships. They showed a fall in torque associated to an increase in angular velocity what was quantified by calculating a damping coefficient (Biso). Both experiments gave consistent results indicating that Bbode was the lowest viscous parameter. This difference is discussed in terms of (i) "analog" viscosity originating from muscle cross-bridges; and (ii) real mechanical damping of passive structures.     

Torque-velocity characteristics and muscle fiber type in human vastus lateralis

The relationship between torque-velocity characteristics of the knee extensors during isokinetic contractions and muscle fiber type of the vastus lateralis, determined from two muscle biopsy samples, was investigated in 12 male and 18 female subjects. Peak torque, corrected for the effect of gravity and impact artifact, was classified as corrected peak torque. The torque measured 30 degrees from full extension and, corrected for gravity, was classified as corrected torque at 30 degrees. No significant correlations were found between the percentage of fast-twitch fibers (%FT) or the relative area of FT fibers (%FTA) and corrected peak torque values for any of the velocities tested or the knee angles where corrected peak torques were measured. However, significant inverse relationships were determined for corrected torque at 30 degrees at all but the fastest velocity (270 degrees/s) and both %FT and %FTA for the male subjects. These results reveal that muscle fiber type of the vastus lateralis, based on duplicate muscle samples, is not related to the peak torque actually generated by the knee extensors but may influence the shape of the torque output for maximal contractions sustained over the entire range of motion.     

Torque-velocity relationship in isokinetic cycling exercise

Seven healthy female subjects performed brief (less than 10 s) periods of maximal exercise on a constant-velocity cycle ergometer, over the functional range of pedaling velocities, and an isometric contraction with each leg. There was an inverse relationship between peak torque and pedal crank velocity in all subjects; isometric torque was (mean +/- SE) 19.8 +/- 8.3% greater than the torque recorded at the slowest velocity of 11 rpm. The torque-velocity relationship was described best by a single exponential equation: y = 189.6 X e-0.0834x, where y is peak torque in Newton . meters and x is crank velocity in revolutions per minute. Peak power was a parabolic function of crank velocity; the data were fitted suitably by a second-order polynomial equation: y = -0.0589x2 + 14.504x + 47.092, where y is peak power in watts and x is crank velocity in revolutions per minute. Maximal peak power occurred at crank velocities ranging from 120 to 160 rpm, when the torque was 0.36 +/- 0.06 of the maximal isometric tension. These results demonstrate the importance of recording velocity in measurements of dynamic maximal power.     

Neuromuscular changes for hopping on a range of damped surfaces.

Humans hopping and running on elastic and damped surfaces maintain similar center-of-mass dynamics by adjusting stance leg mechanics. We tested the hypothesis that the leg transitions from acting like an energy-conserving spring on elastic surfaces to a power-producing actuator on damped surfaces during hopping due to changes in ankle mechanics. To test this hypothesis, we collected surface electromyography, video kinematics, and ground reaction force while eight male subjects (body mass: 76.2 +/- 1.7 kg) hopped in place on a range of damped surfaces. On the most damped surface, most of the mechanical work done by the leg appeared at the ankle (52%), whereas 23 and 25% appeared at the knee and hip, respectively. Hoppers extended all three joints during takeoff further than they flexed during landing and thereby did more net positive work on more heavily damped surfaces. Also, all three joints reached peak flexion sooner after touchdown on more heavily damped surfaces. Consequently, peak moment occurred during joint extension rather than at peak flexion as on elastic surfaces. These strategies caused the positive work during extension to exceed the negative work during flexion to a greater extent on more heavily damped surfaces. At the muscle level, surface EMG increased by 50-440% in ankle and knee extensors as surface damping increased to compensate for greater surface energy dissipation. Our findings, and those of previous studies of hopping on elastic surfaces, show that the ankle joint is the key determinant of both springlike and actuator-like leg mechanics during hopping in place.     

Knee and ankle joint torque-angle relationships of multi-joint leg extension

The force-length-relation (F-l-r) is an important property of skeletal muscle to characterise its function, whereas for in vivo human muscles, torque-angle relationships (T-a-r) represent the maximum muscular capacity as a function of joint angle. However, since in vivo force/torque-length data is only available for rotational single-joint movements the purpose of the present study was to identify torque-angle-relationships for multi-joint leg extension. Therefore, inverse dynamics served for calculation of ankle and knee joint torques of 18 male subjects when performing maximum voluntary isometric contractions in a seated leg press. Measurements in increments of 10° knee angle from 30° to 100° knee flexion resulted in eight discrete angle configurations of hip, knee and ankle joints. For the knee joint we found an ascending-descending T-a-r with a maximum torque of 289.5° ± 43.3 Nm, which closely matches literature data from rotational knee extension. In comparison to literature we observed a shift of optimum knee angle towards knee extension. In contrast, the T-a-r of the ankle joint vastly differed from relationships obtained for isolated plantar flexion. For the ankle T-a-r derived from multi-joint leg extension subjects operated over different sections of the force-length curve, but the ankle T-a-r derived from isolated joint efforts was over the ascending limb for all subjects. Moreover, mean maximum torque of 234.7 ± 56.6 Nm exceeded maximal strength of isolated plantar flexion (185.7 ± 27.8 Nm). From these findings we conclude that muscle function between isolated and more physiological multi-joint tasks differs. This should be considered for ergonomic and sports optimisation as well as for modelling and simulation of human movement.     

A multivariate approach to predicting knee extensor performance

The impact of two predictor variables (estimated knee extensor fast-twitch fiber percentage, body mass) on performance measures (vertical jump power output, leg press peak angular velocity) were examined. Subjects (25 men, 27 women) performed 5 workouts involving 2 vertical jump, leg press, and 50-repetition isokinetic tests (to estimate knee extensor fast-twitch fiber percentage). Multivariate regression determined the following significant (p < 0.05) vertical jump equations: predicted male power output = -59.3464 + 1.566 (estimated knee extensor fast-twitch muscle fiber percent) + 15.7884 (body mass), predicted female power output = 36.1574 + 3.4248 (estimated knee extensor fast-twitch muscle fiber percent) + 9.8633 (body mass). Leg press peak angular velocity equations were insignificant by gender; thus, pooled data yielded the following: predicted leg press peak angular velocity = 18.6187 + 0.235 (estimated knee extensor fast-twitch muscle fiber percent) + 0.3801 (body mass). Body mass explained more variance for each performance measure.     

Changes in force-velocity and power output of upper and lower extremity musculature in young subjects following 20 days bed rest

Ten healthy sedentary students were exposed to 20 days bed rest (BR) to study the effect of simulated weightlessness on force(F)-velocity(V) characteristics and power(P) output of upper and lower limb movements. F, V and P were measured using a special dynamometer applicable to single joint movements [elbow flexion(EF) and extension(EE), knee flexion(KF) and extension(KE), and hip flexion] or multi-joint movements (squatting). Physiological cross-sectional areas(PCSA) of KF and KE muscles were measured by a magnetic resonance imaging technique. After BR, attenuation in P were observed in lower limb movements (decreased by 19.8-43.6% for squatting, KF and KE), in upper limb movements on the other hand, the decreases in P were not significant (approximately -5% for EF and EE). Decrease in P in lower limb were more pronounced in heavier loaded conditions which were characterized by decreases in both F and V. For KF and KE, decreases in maximal static F (-18.9 to approximately -26.8%) were more pronounced than the decreases observed in the PCSA (approximately -7%), resulting in decreases in specific tension (-12.3 to approximately -22.1%). Neural excitation potentials to generate maximal muscle tension or P might also be influenced by weightlessness.     

Isokinetic strength in weight-trainers

Isokinetic strength of ankle plantarflexion (APF), knee extension (KE) and elbow extension (EE) was measured in male weight-trainers (6 power-lifters and 7 bodybuilders) and 25 untrained men of similar age and height. The weight-trainers exceeded control subjects by 21%, 25% and 73% in APF, KE and EE strength respectively. A similar pattern was obtained for limb girth, in which the weight-trainers exceeded control subjects by 6%, 13%, and 31% in calf, thigh and arm girth, respectively. Strength was similarly enhanced in the weight-trainers at the lower and higher velocities (APF 0.10, 0.63 rad X s-1, KE and EE 0.52, 3.14 rad X s-1) tested, and accounted for the positive correlation (r = 0.84) observed between low and high velocity strength. The powerlifters differed significantly from the bodybuilders only in their greater low velocity APF strength. The relatively greater enhancement of upper versus lower limb strength and muscle mass in the weight-trainers was considered in respect to training habits, trainability of different muscle groups and the state of training of muscle groups in untrained men.