Segmental contribution to forces in vertical jump

Summary Performance of a vertical jump was analyzed with respect to the contribution of the different body segments to the forces acting on the whole body center of gravity. Both cinematograph and force-platform techniques were employed. The data disclosed that the take-off velocity in vertical jumps was caused by the different components as follows: knee extension 56%, plantar flexion 22%, trunk extension 10%, arm swing 10%, and head swing 2%. However, the average take-off velocity of the total performance (3.03 m/s) was only 76% from the theoretical maximum calculated from the segmental analyses. Optimal timing of the segmental performances was calculated to increase this efficiency to 84%. Great variance were observed among individuals in the total performance despite the similarities in utilization of the performance of individual segments.     

Force-, power-, and elasticity-velocity relationships in walking,running, and jumping

Summary Ground reaction forces and mechanical power were investigated when the subjects walked normally, while they were racing or running at four speeds, and when they performed the running long jump take-off. In addition, the apparent spring constants of the support leg in eccentric and concentric phases were investigated at the four running speeds, during the running long jump take-off, and in the triple jump. Six club level track and field athletes, four national level long jumpers, and six national level triple jumpers took part in the study. Cinematographic technique and a mathematical model of hopping (Alexander and Vernon 1975) were employed in the analysis. Force and power values were found to vary in the following order (from highest to lowest): long jump take-off, maximal running speed, submaximal running (80, 60, and 40% of maximum speed), racing gait, and normal gait. The data disclosed that the measured parameters had the highest values in the long jump take-off performed by the long jump athletes. Their peak values were: resultant ground reaction force 3270±74 N and mechanical power 160.1±10.5 J×kg^–1×s^–1. For the track and field athletes the values were 2010±80 N and 126.0±12.6 J ×kg^–1×s^–1. The apparent spring constant values of the support leg in the national level jumper group were in eccentric phase 30.54±8.38 N×mm^–1 ×kg^–1 and in concentric phase 0.129±0.012 N×mm^–1×kg^–1. In the track and field athletes the values were 13.97±1.01 N×mm^–1×kg^–1 and 0.093±0.003 N×mm^–1×kg^–1, respectively. In general, the increase in force and mechanical power output was related to the value of the apparent spring constant of the support leg in the eccentric phase. The spring constant in the eccentric phase increased with the velocity of motion in running, the long jump take-off and the triple jump. This suggests that it may be possible to use this parameter as a measure of mechanical performance, as it may reflect the combined elasticity of muscles, tendons, and bones.     

Mechanical efficiency and user power requirement with a pushrim activated power assisted wheelchair

The objective of this study was to quantify the difference in mechanical efficiency and user power generation between traditional manual wheelchairs and a pushrim activated power assisted wheelchair (PAPAW). Ten manual wheelchair users were evaluated in a repeated measures design trial with and without the PAPAW for propulsion efficiency. Subjects propelled a Quickie GP equipped with the PAPAW and their own chair on a computer controlled wheelchair dynamometer at five different resistance levels. Power output, user power with the PAPAW hubs, subjects' oxygen consumption per minute and mechanical efficiency were analyzed. Metabolic energy and user power were significantly lower (p<0.05), and mechanical efficiency significantly higher with the PAPAW than with subjects' own chairs. Subjects needed to generate on average 3.65 times more power when propelling their own wheelchairs as compared to PAPAW. Mean mechanical efficiency over all trials was 80.33% higher with the power assisted hubs. PAPAW provides on average 73% of the total power when subjects propel with power assistance. Significantly increased efficiency and reduced requirement of user power is achieved using the PAPAW. With use, the PAPAW may contribute to delaying secondary injuries of manual wheelchair users. In addition, it may be suitable for people who have (or at risk for) upper extremity joint degeneration, reduced exercise capacity, low strength or endurance who currently use electric powered wheelchairs.     

Mechanical characteristics and fiber composition of human leg extensor muscles

Summary To investigate the influence of skeletal muscle fiber composition on the mechanical performance of human skeletal muscle under dynamic conditions, 34 physical education students with differing muscle fiber composition (M. vastus lateralis) were used as subjects to perform maximal vertical jumps on the force-platform. Two kinds of jumps were performed: one from a static starting position (SJ), the other with a preliminary counter-movement (CMJ). The calculated mechanical parameters included height of rise of center of gravity (h), average force (¯F), net impulse (NI) and average mechanical power (W). It was observed that the percentage of fast twitch fibers was significantly related (p< 0.05-0.01) to these variables in SJ condition and also to h and NI of the positive work phase in CMJ. It is concluded that skeletal muscle fiber composition also determines performance in a multijoint movement. The result is explainable through the differences in the mechanical characteristics of the motor units and their respective muscle fibers.     

Mechanical power during maximal treadmill walking and running in young and elderly men

This study determined mechanical power during movements specific to maximal walking and running using a non-motorized treadmill in 38 elderly [69.4 (5.0) years] and 50 young [24.3 (3.4) years] men. The mean mechanical power over a period of time covering six steps, during which the belt velocity peaked and then kept almost plateau, was determined as a performance score in each of maximal walking (WP) and running (RP). In terms of the value relative to body mass, the relative difference between the two age groups was greater for RP (61.7%) than for WP (21.4%) or isometric knee extension (34.1%) and flexion torque (43.8%). In the two groups, WP was significantly (P<0.05) correlated to knee extension (r=0.582 for the elderly and r=0.392 for the young) and flexion torque (r=0.524 for the elderly and r=0.574 for the young). Similarly, RP was also significantly (P<0.05) correlated to knee extension (r=0.627 for the elderly and r=0.478 for the young) and flexion torque (r=0.500 for the elderly and r=0.281 for the young). In these relationships, the WP adjusted statistically by thigh muscle torque was similar in the two age groups. However, the corresponding value for RP was significantly higher in the young than in the elderly. The findings here indicate that: (1) the difference between the young and elderly men in mechanical power is greater during maximal running than maximal walking, and (2) although the thigh muscle torque contributes to the power production during the two maximal exercise modes in the two age groups, the RP is greater in the young than in the elderly regardless of the difference in the thigh muscle torque.     

Acute changes in muscle activation and leg extension performance after different running exercises in elite long distance runners

This study investigated acute changes in muscle activation and muscular power performance after three different running exercises in elite long-distance runners. Twenty-two nationally and internationally ranked long-distance runners performed first an incremental treadmill running test until exhaustion (MR) and then 40 min continuous (TR) and intermittent (2 min run/2 min rest) (IR) running exercises at an intensity of 80 and 100% of the velocity associated with VO_2max, respectively. Muscle activation and muscular power performance tests (counter-movement jumps, CMJ, and a set of ten maximal half squats from the static starting position with an extra load of 35% of the subjects,′ one repetition maximum) were performed before and immediately after the runs. The average mechanical power (P) of the half squats was calculated and the root mean square electromyogram (EMGrms) from the vastus lateralis, vastus medialis, gastrocnemius and biceps femoris muscles was recorded simultaneously during the half squat performances. The results showed an acute exercise–induced increase in P (ANOVA time effect, P=0.000) together with a reduction in EMGrms of the knee extensor muscles (ANOVA time effect, P=0.000). However, mechanical P expressed as a relative change within the set decreased after MR. In TR the improvement in P correlated positively with the maximal running performance of the runners (P<0.05), while in IR it correlated negatively (P<0.05). Jumping performance was significantly enhanced after each run (P<0.001, for all) and the improvement correlated negatively with the maximal sprinting speed and maximal jumping height of the runners (P<0.01, for all). It is concluded that in elite long distance runners an intensive prolonged running exercise reduces the surface EMG of the knee extensor muscles, and may lead to a different coordination strategy in leg extension exercises performed into the vertical direction. After continuous type of running the power improvement correlates positively with maximal endurance running capacity, whereas after intermittent type of running it correlates negatively.     

On the mechanical power of joint extensions as affected by the change in muscle force (or cross-sectional area), ceteris paribus

This paper offers a reference prediction for the changes of mechanical power generated during a maximal (vertical, horizontal or inclined) joint extension, as a consequence of just the changes of muscle force or cross-sectional area (CSA). Ceteris paribus (all other things being equal), for a given joint, the exponents at which the force changes have to be raised to predict the duration, final speed and power of the maximal extension are –0.5, 0.5, and 1.5, respectively, for horizontal movements. For example, a force decrease of 30% leads to an increase of 19.5% of the duration of the extension and to a decrease of 16.3% and of 41.4% of its final speed and power. The equations for vertical or inclined extension performances are subject to the same exponents. However, the actual prediction is dependent upon the ratio between muscle strength and body weight, reflecting the fraction of the muscle strength (or CSA) acting against gravity during the manoeuvre. For instance, during a vertical extension, a force decrease of 30% leads to an increase of 30.9% of the duration of the extension and to a decrease of 29.3% and of 50.5% of its final speed and power. Based on the proposed model, a methodology is also described to detect the effects on the extension power of other determinants, in addition to CSA, of the useful force change (e.g. neuromuscular factors, motor control). Electronic Publication     

Measurement and Characterization of Whole-Cell Mechanical Behavior

An understanding of whole-cell mechanical behavior can provide insight into cellular responses to mechanical loading and diseases in which such responses are altered. However, this aspect of cellular mechanical behavior has received limited attention. In this study, we used the atomic force microscope (AFM) in conjunction with several mechanical characterization methods (Hertz contact theory, an exponential equation, and a parallel-spring recruitment model) to establish a mechanically rigorous method for measuring and characterizing whole-cell mechanical behavior in the deformation range 0–500 nm. Using MC3T3-E1 osteoblasts, measurement repeatability was assessed by performing multiple loading cycles on individual cells. Despite variability in measurements, repeatability of the measurement technique was statistically confirmed. The measurement technique also proved acceptable since only 5% of the total variance across all measurements was due to variations within measurements for a single cell. The parallel-spring recruitment model, a single-parameter model, accurately described the measured nonlinear force–deformation response (R ² > 0.99) while providing a mechanistic explanation of whole-cell mechanical behavior. Taken together, the results should improve the capabilities of the AFM to probe whole-cell mechanical behavior. In addition, the success of the parallel-spring recruitment model provides insight into the micromechanical basis of whole-cell behavior.     

Differences in mechanical efficiency between power- and endurance-trained athletes while jumping

Mechanical efficiency (ME) of jumping exercises was compared between power-trained (n = 11) and endurance-trained athletes (n = 10) using both a biomechanical and a physiological approach. In drop jumps and in stretch-shortening cycle exercise on a special sledge (sledge jumps), the subjects performed 60 muscle actions from a dropping height of optimum minus 40 cm (O – 40), as well as from dropping heights of optimum (O) and optimum plus 40 cm (O + 40). Thus, they were tested in six different tests which lasted for a total of 3 min for each. The mean ME values in the drop jumps from the lowest dropping height upwards were as follows: 23.8 (SD 5.3)%, 35.5 (SD 10.8)% and 39.2 (SD 6.6)% for the power group, and 30.8 (SD 6.5)%, 37.5 (SD 8.7)% and 41.4 (SD 7.0)% for the endurance group. In the sledge jumps the ME values were 37.0 (SD 5.6)%,48.4 (SD 4.0)% and 54.9 (SD 8.5)% for the power group, and 40.2 (SD 5.9)%, 46.9 (SD 5.7)% and 58.5 (SD 5.5)% for the endurance group. As can be seen, the ME values increased with increasing stretch load. However, the groups did not differ from each other except in the drop jump condition of O – 40 (P < 0.05). The higher power (P < 0.001) among the power athletes in every measured condition was associated with a faster rate of electromyogram development during the pre-activity, and smoother muscle activity patterns in the ground contact. On the other hand, the endurance athletes had a lower blood lactate concentration after every test, and in addition a lower heart rate and ventilation during the sledge jumps than their power counterparts. Therefore, it would seem that the similar mean ME values between the subject groups could be explained by improved function of the neuromuscular system among the power group and improved metabolism among the endurance group.     

Mechanical and dimensional adaptation of rabbit carotid artery culturedin vitro

The effects of the mechanical environment on arterial walls were investigated in rabbit common carotid arteries, cultured for six days under three different intraluminal pressures (0, 80 and 160 mmHg) in a perfusion culture system. The mechanical responses following the culture were examined using a quasi-static pressure-diameter test. Specimen viability was determined by smooth muscle contraction induced with KCl. Eighteen out of 21 cultured segments showed a peak reduction in diameter of more than 10% and were used for the analysis. The arterial segments cultured at 0 mmHg had a significantly smaller diameter than those cultured at other pressures. The segments cultured at higher pressure had lower incremental elastic moduli at 20 and 80 mmHg and higher moduli at 160 mmHg. The walls of the cultured segments were thicker in groups with higher pressure. These results indicate that, even in culture, the mechanical environment is a major determinant for the mechanical property and dimensions of the arterial wall. Arterial walls may respond to their mechanical environment even if other factors, such as hormonal environment and nervous stimuli, are kept unchanged.     

Mechanical and dimensional adaptation of rabbit carotid artery culturedin vitro

The effects of the mechanical environment on arterial walls were investigated in rabbit common carotid arteries, cultured for six days under three different intraluminal pressures (0, 80 and 160 mmHg) in a perfusion culture system. The mechanical responses following the culture were examined using a quasi-static pressure-diameter test. Specimen viability was determined by smooth muscle contraction induced with KCl. Eighteen out of 21 cultured segments showed a peak reduction in diameter of more than 10% and were used for the analysis. The arterial segments cultured at 0 mmHg had a significantly smaller diameter than those cultured at other pressures. The segments cultured at higher pressure had lower incremental elastic moduli at 20 and 80 mmHg and higher moduli at 160 mmHg. The walls of the cultured segments were thicker in groups with higher pressure. These results indicate that, even in culture, the mechanical environment is a major determinant for the mechanical property and dimensions of the arterial wall. Arterial walls may respond to their mechanical environment even if other factors, such as hormonal environment and nervous stimuli, are kept unchanged.     

Adaptation of reach-to-grasp movement in response to force perturbations

This study examined how reach-to-grasp movements are modified during adaptation to external force perturbations applied on the arm during reach. Specifically, we examined whether the organization of these movements was dependent upon the condition under which the perturbation was applied. In response to an auditory signal, all subjects were asked to reach for a vertical dowel, grasp it between the index finger and thumb, and lift it a short distance off the table. The subjects were instructed to do the task as fast as possible. The perturbation was an elastic load acting on the wrist at an angle of 105 deg lateral to the reaching direction. The condition was modified by changing the predictability with which the perturbation was applied in a given trial. After recording unperturbed control trials, perturbations were applied first on successive trials (predictable perturbations) and then were applied randomly (unpredictable perturbations). In the early predictable perturbation trials, reach path length became longer and reaching duration increased. As more predictable perturbations were applied, the reach path length gradually decreased and became similar to that of control trials. Reaching duration also decreased gradually as the subjects adapted by exerting force against the perturbation. In addition, the amplitude of peak grip aperture during arm transport initially increased in response to repeated perturbations. During the course of learning, it reached its maximum and thereafter slightly decreased. However, it did not return to the normal level. The subjects also adapted to the unpredictable perturbations through changes in both arm transport and grasping components, indicating that they can compensate even when the occurrence of the perturbation cannot be predicted during the inter-trial interval. Throughout random perturbation trials, large grip aperture values were observed, suggesting that a conservative aperture level is set regardless of whether the reaching arm is perturbed or not. In addition, the results of the predictable perturbations showed that the time from movement onset to the onset of grip aperture closure changed as adaptation occurred. However, the spatial location where the onset of finger closure occurred showed minimum changes with perturbation. These data suggest that the onset of finger closure is dependent upon distance to target rather than the temporal relationship of the grasp relative to the transport phase of the movement.     

Mechanical model for the simulation of ischaemia and infarction of the left ventricle

Several ischaemic states, including immediate infarction, occurring in a canine left ventricle at the onset of the ejection phase and affecting regions of varying sizes are simulated, employing a recently developed comprehensive finite-element model. The analysis assumes an instantaneous partial or complete loss of contractility in the damaged region, whereas the passive mechanical properties of the tissue are yet unaltered. The results indicate a progressive deterioration of the cardiac performance, as well as considerable geometrical changes in the kinematics of the whole ventricle, directly related to both ischaemia level and the ischaemic region size. Owing to the reduction in the stroke volume, the simulation predicts a degradation of up to 33 per cent in the ejection fraction for an infarct affecting 43 per cent of the ventricular wall volume. A quantitative relationship between the ejection fraction, the level of ischaemia and the size of the ischaemic zone is derived and presented.     

The contribution of the pulmonary microvascular pressure in the maintenance of an open lung during mechanical ventilation

Changes in pulmonary hemodynamics modify the mechanical properties of the lungs. The effects of alterations in pulmonary capillary pressure (Pc) were investigated on the airway and lung tissue mechanics during positive-pressure ventilation and following lung recruitment maneuvers. Isolated, mechanically normoventilated (PEEP 2.5 cmH(2)O) rat lungs were perfused with Pc set to 0 (unperfused), 5, 10 or 15 mmHg, in random sequence. The pulmonary input impedance (ZL) was measured at end-expiration before and after a 10-min long ventilation. After inflation of the lung to 30 cmH(2)O during P-V curve recordings, another set of ZL was measured to evaluate the degree of recruitment. The PEEP was then decreased to 0.5 cmH(2)O and the sequence was repeated. Airway resistance and parenchymal damping and elastance (H) were estimated from ZL by model fitting. From the P-V curves, elastance (E) and hysteresis indices were determined. Mechanical ventilation at both PEEP levels resulted primarily in elevations in the tissue parameters, with the greatest increases at the 0 Pc level (H changes of 27.8+/-4.2 and 61.3+/-3.7% at 2.5 and 0.5 cmH(2)O PEEP, respectively). The maintenance of physiological Pc (10 mmHg) led to a significantly lower elevation in H (11.6+/-1.5% versus 31.4+/-3.6%). The changes in the oscillatory mechanics were also reflected in E and the hysteresis of the P-V curves. These findings indicate that pulmonary hypoperfusion during mechanical ventilation forecasts a parenchymal mechanical deterioration. Physiological pressure in the pulmonary capillaries is therefore an important mechanical factor promoting maintenance of the stability of the alveolar architecture during positive-pressure mechanical ventilation.     

In vivo human triceps surae and quadriceps femoris muscle function in a squat jump and counter movement jump

An optic fibre method was used to measure in humans in vivo Achilles (ATF) and patellar tendon forces (PTF) during submaximal squat jumps (SJ) and counter movement jumps (CMJ). Normal two-legged jumps on a force plate and one-legged jumps on a sledge apparatus were made by four volunteers. Kinetics, kinematics, and muscle activity from seven muscles were recorded. The loading patterns of the tendomuscular system differed among the jumping conditions, but were similar when the jumping height was varied. Peak PTF were greater than ATF in each condition. In contrast to earlier simulation studies it was observed that tendomuscular force could continue to increase during the shortening of muscle-tendon unit in CMJ. The concentric tendomuscular output was related to the force at the end of the stretching phase while the enhancement of the output in CMJ compared to SJ could not be explained by increases in muscle activity. The stretching phase in CMJ was characterised by little or no electromyogram activity. Therefore, the role of active stretch in creating beneficial conditions for the utilisation of elastic energy in muscle was only minor in these submaximal performances. The modelling, as used in the present study, showed, however, that tendon underwent a stretch-shortening cycle, thus having potential for elastic energy storage and utilisation. In general, the interaction between muscle and tendon components may be organised in a manner that takes advantage of the basic properties of muscle at given submaximal and variable activity levels of normal human locomotion. Accepted: 28 June 2000     

Jumping to conclusions and perceptions in early psychosis: Relationship with delusional beliefs

Introduction. Previous research has suggested that biases in cognitive processes involved in everyday reasoning may contribute to the development of delusional beliefs. The aim of this study was to explore jumping to conclusions (JTC), a data-gathering bias, and jumping to perceptions (JTP), a bias towards believing ambiguous perceptual events are real and external.

Methods. Individuals with current delusions (n=17), remitted delusions (n=17), both recruited from an early psychosis service, and nonclinical participants (n=35) were compared on a probabilistic reasoning task, an auditory perceptual bias task, and the Barely Visible Words task.

Results. The deluded participants did not demonstrate the expected JTC bias; therefore the relationship between JTC and JTP could not be examined. However, both clinical groups exhibited a JTP bias on the auditory perceptual bias task. In contrast, the lowered perceptual threshold for threat displayed by the control group was absent in the clinical groups.

Conclusions. These results suggest that the JTP bias may be a trait characteristic in those with a propensity to delusions, and that these individuals may also show a bias away from threat.     

Relative contribution of aging and menopause to changes in lean and fat mass in segmental regions

Objective: The aim of the study was to investigate the relative contribution of aging and menopause to the changes in lean and fat mass in segmental regions. Materials and methods: Subjects were 365 pre- and 201 postmenopausal Japanese women aged between 20 and 70 years old. Age, height, weight, body mass index (BMI, Wt/Ht²), age at menopause, years since menopause (YSM), and menopausal status were recorded. Lean and fat mass of the arms, trunk, legs, total body, and the ratio of trunk fat mass to leg fat mass amount (trunk–leg fat ratio) were measured by dual-energy X-ray absorptiometry (DEXA). Regional (arms, lumbar spine, pelvis, legs, and total body) bone mineral density (BMD) were measured by DEXA. Results: Total body lean mass and regional BMD decreased (P<0.001), while percentage of body fat, trunk fat mass, and trunk–leg fat ratio increased (P<0.001) with aging and after menopause. On multiple regression analyses, trunk and total body lean mass were inversely correlated with menopausal status (P<0.001 and 0.05, respectively) but not with age. Trunk fat mass, trunk–leg fat ratio, and percentage of body fat were positively correlated with age (P<0.01) but not with menopausal status. Regional BMD were more inversely correlated with menopausal status (P<0.001) than age. Conclusion: Decrease in lean mass and BMD are more menopause-related, while the shift toward upper body fat distribution and overall adiposity are more age-related. Lean tissue is similar to bone tissue from the viewpoint of more undergoing menopausal effect.     

Electromyogram mean power frequency in non-fatigued trapezius muscle

Summary In this study we have examined the variation of mean power frequency (MPF) in the electromyogram (EMG) from the non-fatigued trapezius muscle, with different external hand loads, in different shoulder joint positions, different torques and different planes of movement. The study was limited to the functional range of movement in the shoulder joint. It was performed on 19 healthy subjects. Surface EMG was recorded, analysed by means of a computer programme and examined by regression analysis. Normalized MPF values were calculated by dividing the MPF by the individual average MPF for all positions and loads. The results indicated no major variation in normalized MPF. The largest systematic variation of normalized MPF, ±8%, was related to joint angle. We have concluded that the MPF value obtained initially can be used within the functional range of movement to calculate the relative decrease in MPF as a result of muscle fatigue, and that the decrease is significant if it exceeds 8% of the initial value.     

Effect of muscle temperature on leg extension force and short-term power output in humans

Summary The effect of changing muscle temperature on performance of short term dynamic exercise in man was studied. Four subjects performed 20 s maximal sprint efforts at a constant pedalling rate of 95 crank rev · min⁻¹ on an isokinetic cycle ergometer under four temperature conditions: from rest at room temperature; and following 45 min of leg immersion in water baths at 44; 18; and 12‡ C. Muscle temperature (Tm) at 3 cm depth was respectively 36.6, 39.3, 31.9 and 29.0‡ C. After warming the legs in a 44‡ C water bath there was an increase of ∼11% in maximal peak force and power (PP_max) compared with normal rest while cooling the legs in 18 and 12‡ C water baths resulted in reductions of ∼12% and 21% respectively. Associated with an increased maximal peak power at higher Tm was an increased rate of fatigue. Two subjects performed isokinetic cycling at three different pedalling rates (54, 95 and 140 rev · min⁻¹) demonstrating that the magnitude of the temperature effect was velocity dependent: At the slowest pedalling rate the effect of warming the muscle was to increase PP_max by ∼2% per ‡ C but at the highest speed this increased to ∼10% per ‡ C.     

Ergometry for estimation of mechanical power output in sprinting in humans using a newly developed self-driven treadmill

An evaluation of mechanical power during walking and running in humans was undertaken after developing a specially designed running ergometer (RE) in which the subjects gripped the handlebar in front of them keeping both arms straight and in a horizontal position. Ten subjects participated in comparisons of the mean horizontal pushing force (MF _am) on the handlebar with the mean horizontal ground reaction force (MF _fp) recorded by force platform under the RE during five different constant speeds of walking or running and sprint running with maximal effort. Mechanical power developed during sprint running on the RE was compared with a 50 m sprint. Mean linear velocity (Mv) of the RE belt was recorded by the rotary encoder attached to the axis of the belt. Mean mechanical power calculated from the handlebar setting (MP _am=MF _am × Mv) was compared to that calculated from force platform recordings (MP _fp=MF _fp × Mv). A high test-retest reproducibility was observed for both MF _fp (r=0.889) and MF _am (r=0.783). Larger values for the coefficient of variation for MF _am (11.3%–15.8%) were observed than for MF _fp (3.3%–8.2%). The MP _am, which were obtained from five different constant speeds of walking, running and sprint running were closely correlated to those of MP _fp (y=0.98x − 19.10,r=0.982, P < 0.001). In sprint running, MP _am was 521.7 W (7.67 W · kg⁻¹) and was correlated to the 50 m sprint time (r=−0.683, P < 0.01). It is concluded that the newly developed RE was useful in the estimation of mechanical power output during human locomotion such as when walking, jogging and sprinting. Accepted: 10 October 2000