Gear ratios at the limb joints of jumping dogs

An increase in gear ratio of the limb extensor muscles during joint extension has been suggested to be a mechanism that facilitates optimal power production by skeletal muscles. The objectives of this study were to: (1) measure gear ratios at the wrist, elbow, shoulder, ankle, knee, and hip joints of jumping dogs, (2) compute the work performed by each of these joints, and (3) measure muscle shortening velocity for a joint exhibiting an increasing gear ratio during joint extension. The gear ratio out-lever was computed by dividing the ground reaction force (GRF) moment by the GRF, whereas the in-lever was directly measured as the perpendicular distance from the joint center to the line of action of the extensor muscle. In addition, changes in fascicle length were measured from the vastus lateralis muscle using sonomicrometry. Of the joints examined, only the gear ratios at the shoulder and knee joints increased during jumping in a manner that could facilitate peak power production of actively shortening muscles. The vastus lateralis was found to shorten at an average velocity of 3.20 muscle lengths per second. This is similar to estimates of shortening velocity that produce peak muscular power in mammals the size of dogs. Additionally, the knee extensors were found to produce a large proportion (26.6%) of the positive external work of the limbs. These observations suggest that dynamic gearing in jumping dogs may allow the extensor muscles of the knee joint to shorten in a way that maximizes their power production.     

Effects of external loading on short term power output in children and young male adults

The effects of external loading, in the form of small weights distributed evenly over the limbs and torso, on physical performance and power output have been studied during vertical jumping in 10 children and four young adults and the results compared with maximal cycling. The results show under control (unloaded) conditions the absolute peak power output (W) achieved by children and adults was 572 W (45%) and 765 W (25%) respectively higher in cycling than jumping. The addition of weights during jumping served only to increase this difference. External loading produced a linear decrease of W in both groups of subjects. The reduction in W was entirely due to a decrease of take-off velocity (VT). The relationship between VT and added weights (delta wt) could be described by the equations: VT (ms-1) = 1.91 - 0.042 delta wt (kg); r = -0.96 (children); VT (ms-1) = 2.49 - 0.021 delta wt (kg); r = -0.99 (adults). Thus, contrary to the recent work of Caiozzo and Kyle (1980) which involved stair-climbing, body size and speed of movement in children and young adults would appear to be optimally matched for the production of lifting work during vertical jumping. External loading reduces the generation of power output immediately prior to take-off of a maximal jump from a force platform.     

Muscle mechanical work requirements during normal walking: the energetic cost of raising the body's center-of-mass is significant

Inverted pendulum models of walking predict that little muscle work is required for the exchange of body potential and kinetic energy in single-limb support. External power during walking (product of the measured ground reaction force and body center-of-mass (COM) velocity) is often analyzed to deduce net work output or mechanical energetic cost by muscles. Based on external power analyses and inverted pendulum theory, it has been suggested that a primary mechanical energetic cost may be associated with the mechanical work required to redirect the COM motion at the step-to-step transition. However, these models do not capture the multi-muscle, multi-segmental properties of walking, co-excitation of muscles to coordinate segmental energetic flow, and simultaneous production of positive and negative muscle work. In this study, a muscle-actuated forward dynamic simulation of walking was used to assess whether: (1). potential and kinetic energy of the body are exchanged with little muscle work; (2). external mechanical power can estimate the mechanical energetic cost for muscles; and (3.) the net work output and the mechanical energetic cost for muscles occurs mostly in double support. We found that the net work output by muscles cannot be estimated from external power and was the highest when the COM moved upward in early single-limb support even though kinetic and potential energy were exchanged, and muscle mechanical (and most likely metabolic) energetic cost is dominated not only by the need to redirect the COM in double support but also by the need to raise the COM in single support.     

The weak link: do muscle properties determine locomotor performance in frogs?

Muscles power movement, yet the conceptual link between muscle performance and locomotor performance is poorly developed. Frog jumping provides an ideal system to probe the relationship between muscle capacity and locomotor performance, because a jump is a single discrete event and mechanical power output is a critical determinant of jump distance. We tested the hypothesis that interspecific variation in jump performance could be explained by variability in available muscle power. We used force plate ergometry to measure power produced during jumping in Cuban tree frogs (Osteopilus septentrionalis), leopard frogs (Rana pipiens) and cane toads (Bufo marinus). We also measured peak isotonic power output in isolated plantaris muscles for each species. As expected, jump performance varied widely. Osteopilus septentrionalis developed peak power outputs of 1047.0 ± 119.7 W kg(-1) hindlimb muscle mass, about five times that of B. marinus (198.5 ± 54.5 W kg(-1)). Values for R. pipiens were intermediate (543.9 ± 96.2 W kg(-1)). These differences in jump power were not matched by differences in available muscle power, which were 312.7 ± 28.9, 321.8 ± 48.5 and 262.8 ± 23.2 W kg(-1) muscle mass for O. septentrionalis, R. pipiens and B. marinus, respectively. The lack of correlation between available muscle power and jump power suggests that non-muscular mechanisms (e.g. elastic energy storage) can obscure the link between muscle mechanical performance and locomotor performance.     

Does performance of hang power clean differentiate performance of jumping, sprinting, and changing of direction?

The primary purpose of this study was to investigate whether the athlete who has high performance in hang power clean, a common weightlifting exercise, has high performances in sprinting, jumping, and changing of direction (COD). As the secondary purpose, relationships between hang power clean performance, maximum strength, power and performance of jumping, sprinting, and COD also were investigated. Twenty-nine semiprofessional Australian Rules football players (age, height, and body mass [mean +/- SD]: 21.3 +/- 2.7 years, 1.8 +/- 0.1 m, and 83.6 +/- 8.2 kg) were tested for one repetition maximum (1RM) hang power clean, 1RM front squat, power output during countermovement jump with 40-kg barbell and without external load (CMJ), height of CMJ, 20-m sprint time, and 5-5 COD time. The subjects were divided into top and bottom half groups (n = 14 for each group) based on their 1RM hang power clean score relative to body mass, then measures from all other tests were compared with one-way analyses of variance. In addition, Pearson's product moment correlations between measurements were calculated among all subjects (n = 29). The top half group possessed higher maximum strength (P < 0.01), power (P < 0.01), performance of jumping (P < 0.05), and sprinting (P < 0.01). However, there was no significant difference between groups in 5-5 COD time, possibly because of important contributing factors other than strength and power. There were significant correlations between most of, but not all, combinations of performances of hang power clean, jumping, sprinting, COD, maximum strength, and power. Therefore, it seems likely there are underlying strength qualities that are common to the hang power clean, jumping, and sprinting.     

Vertical jumping in Galago senegalensis: the quest for an obligate mechanical power amplifier

Bushbabies (Galago senegalensis) are renowned for their phenomenal jumping capacity. It was postulated that mechanical power amplification must be involved. Dynamic analysis of the vertical jumps performed by two bushbabies confirms the need for a power amplifier. Inverse dynamics coupled to a geometric musculo-skeletal model were used to elucidate the precise nature of the mechanism powering maximal vertical jumps. Most of the power required for jumping is delivered by the vastus muscle-tendon systems (knee extensor). Comparison with the external joint-powers revealed, however, an important power transport from this extensor (about 65%) to the ankle and the midfoot via the bi-articular calf muscles. Peak power output likely implies elastic recoil of the complex aponeurotic system of the vastus muscle. Patterns of changes in length and tension of the muscle-tendon complex during different phases of the jump were found which provide strong evidence for substantial power amplification (times 15). It is argued here that the multiple internal connective tissue sheets and attachment structures of the well-developed bundles of the vastus muscle become increasingly stretched during preparatory crouching and throughout the extension phase, except for the last 13 ms of the push-off (i.e. when power requirements peak). Then, tension in the knee extensors abruptly falls from its maximum, allowing the necessary fast recoil of the tensed tendon structures to occur.     

Explosive jumping: extreme morphological and physiological specializations of Australian rocket frogs (Litoria nasuta)

Abstract Anuran jumping is an ideal system for examining the relationships between key morphological, physiological, and kinematic parameters. We used the Australian rocket frog (Litoria nasuta) as a model species to investigate extreme specialization of the vertebrate locomotor system for jumping. We measured the ground reaction forces applied during maximal jumps using a custom-designed force platform, which allowed us to calculate instantaneous measures of acceleration, velocity, power output, and total jump distance. We quantified the mechanical properties of the plantaris longus muscle using the work loop technique. We found that L. nasuta achieved the second-longest relative jumping distance for any anuran (55.2 body lengths for one individual) and the highest published anuran values for isolated net mean muscle power output measured using work loops (93.5 W kg(-1) muscle mass), hindlimb length to snout-vent length ratio (2.02), and relative hindlimb muscle mass (33% of body mass). Litoria nasuta also had a higher ratio of tibia length to snout-vent length than 19 related species. We found that the mean power output expended during the takeoff phase of jumping in the individual that jumped the farthest was about three times greater than our estimate of available muscle power output.     

Gender bias in jumping kinetics in National Collegiate Athletic Association Division I basketball players

The purposes of this study are to examine gender differences in the contribution of the arm swing to jump height in men and women basketball players and to examine the role of upper-body strength in the contribution of arm swing to jump height. National Collegiate Athletic Association Division I basketball players (men n = 13, women n = 12) performed 4 jumping movements: squat jumps with hands on hips (SNA) and with arm swings (SA) and countermovement jumps with hands on hips and with arm swings (CMA). Differences were found between the jump heights of men and women. Use of the arms increased the jump height of men more than women. Compared with the SNA, the SA allowed an increase of 7 cm (23%) for men and 4 cm (17%) for women. The CMA allowed for an increase of 10 cm (30%) for men and 6 cm (24%) for women. General upper-body strength measures did not correlate strongly with the effect of arms on jumping, but peak power did. As in previous studies, peak power had a high correlation with jumping performance. These results show that the arm swing contributes significantly to jump performance in both men and women basketball players and that strength training for jumping should focus on power production and lifting exercises that are jump specific.     

Mechanical power test and fiber composition of human leg extensor muscles

The present study was undertaken to assess the relationship between the mechanical power developed during new anaerobic power test and muscular fiber distribution. Ten track and field male athletes were used as subjects, whose muscle fiber composition (m. vastus lateralis) varied from 25 to 58 fast twitch (FT) fibers. The test consisted of measuring the flight time with a special timer during 60 s continuous jumping. A formula was derived to allow the calculation of mechanical power during a certain period of time (e.g., in the present study every 15 s during 60 s of jumping performance). The relationship between the mechanical power for the first 15 s period correlated best with fast twitch (FT) fiber distribution (r = 0.86, p less than 0.005). However, the power output during the successive 15 s periods demonstrated lower correlation with FT, and this relationship became statistically non-significant after 30 s of work. The sensitivity to fatigue of the test was supported by the relationship observed between the decrease of power during 60 s jumping performance and the percentage of FT fibers (r = 0.73, p less than 0.01). Thus, the present findings suggest that muscular performance, as determined by the new jumping test, is influenced by skeletal muscle fiber composition. The new test, which primarily evaluates maximal short term muscular power, also proved sensitive in assessing fatigue patterns during 60 s of strenuous work.     

Force, work and power output of lower limb muscles during human maximal-effort countermovement jumping.

The purpose of this study was to simulate human maximal-effort countermovement jumping with a three-dimensional neuromusculoskeletal model. The specific aim was to investigate muscle force, work and power output of major lower limb muscles during the motion. A neuromusculoskeletal model that has nine rigid body segments, 20 degrees of freedom, 32 Hill-type lower limb muscles was developed. The neural activation input signal was represented by a series of step functions with step duration of 0.05 s. The excitation-contraction dynamics of the contractile element, the tissues around the joints to limit the joint range of motion, as well as the foot-ground interaction were implemented. A simulation was started from a standing posture. Optimal pattern of the activation input signal was searched through numerical optimization with a goal of maximizing the height reached by the mass center of body after jumping up. As a result, feasible kinematics, ground reaction force profile and muscle excitation profile were generated. It was found that monoarticular muscles had major contributions of mechanical work and power output, whereas biarticular muscles had minor contributions. Hip adductors, abductors and external rotator muscles were vigorously activated, although their mechanical work and power output was minor because of their limited length change during the motion. Joint flexor muscles such as m. iliopsoas, m. biceps femoris short head and m. tibialis anterior were activated in the beginning of the motion with an effect of facilitating the generation of a countermovement.     

The acute effects of a single set of contrast preloading on a loaded countermovement jump training session

The aim of this research was to assess the effect of a single set of contrast preloading on peak vertical displacement (PD) during a loaded countermovement jump (LCMJ) training session. Nine strength-trained males participated in 2 randomly assigned, crossover design testing sessions consisting of 5 sets of 6 repetitions of 20-kg LCMJs with 3-minute rest intervals between sets. The preloading intervention was performed 3 minutes after the first set and 4 minutes before the second set of 20-kg LCMJs. The control (CON) group performed 1 set of 20-kg LCMJs, whereas the jump squat (JS) group performed 1 set of 40-kg LCMJs. The number of repetitions performed during each preloading condition was varied to match total concentric work between the 2 sessions. A significant (p < 0.05) preload x set interaction for PD was observed, with the JS group jumping significantly higher during the third set performed after the preload in comparison with the CON group. Analysis of peak power output and mean power output during the concentric movement for this set revealed that as the knee flexion angle increased, the effect of the preload was augmented. These results suggest that a single set of preloading exercises enhances performance during a lower-body explosive power training session; however, the effects of a single preloading set may not peak until midway through the training session.     

Behavior of fascicles and tendinous structures of human gastrocnemius during vertical jumping.

Behavior of fascicles and tendinous structures of human gastrocnemius medialis (MG) was determined by use of ultrasonography in vivo during jumping. Eight male subjects jumped vertically without countermovement (squat jump, SQJ). Simultaneously, kinematics, kinetics, and electromyography from lower leg muscles were recorded during SQJ. During phase I (-350 to -100 ms before toe-off), muscle-tendon complex (MTC) length was almost constant. Fascicles, however, shortened by 26%, and tendinous structures were stretched by 6%, storing elastic energy of 4.9 J during phase I. During phase II (-100 ms to toe-off), although fascicles generated force quasi-isometrically, MTC shortened rapidly by 5.3%, releasing prestored elastic energy with a higher peak positive power than that of fascicles. Also, the compliance of tendinous structures in vivo was somewhat higher than that of external tendon used in the simulation studies. The results demonstrate that the compliance of tendinous structures, together with no yielding of muscle fibers, allows MTC to effectively generate relatively large power at a high joint angular velocity region during the last part of push-off.     

Maximum aerobic power and body composition in healthy East African older male and female subjects

The relationship of body size and composition to maximum aerobic power output during work on a bicycle ergometer has been examined in older African subjects divided into three groups: Active men and inactive men and women. Comparison is made with similar data obtained on young African subjects (Davies, Mbelwa, Crockford and Weiner, '73). The results show that in the older men and women, in contrast to the young African subjects, there was complete lack of association between physiological function and body size and structure. In this latter group max was completely independent of body weight, lean body mass, and estimates of leg muscle volume. These findings confirm and extend the work of Davies ('72b) on Europeans and suggest that the main determinant of aerobic power output in older men irrespective of ethnic origin is more closely related to transport and utilization of O₂ within a given active muscle mass than to the total quantity of muscle available to perform the work.     

Muscular strength and jumping performance relationships in young women athletes

The relationships between muscular strength and vertical jumping performance were examined in young women (14-19 years) track and field jumpers (n = 20) and volleyball players (n = 21). The knee extensor muscular strength measured at 9 knee angles was correlated with jumping height and peak power at the squat (SJ) and the countermovement (CMJ) vertical jump tests. Pearson product coefficient of correlation was used to test the significance of these relationships (p 0.80). Specifically, in the volleyball players, the strong relationships were noted for muscular strength at the knee angle range of 40 degrees to 90 degrees and CMJ jumping height as well as SJ peak power. Results indicate the dissimilarity in the relationships between the knee extensor muscular strength and jumping performance in the young female track and field jumpers and volleyball players. In addition, it appears that the measure selected to evaluate jumping performance alters the correlational results.     

Air resistance and its influence on the biomechanics and energetics of sprinting at sea level and at altitude

Following an examination of the processes by which chemical energy is converted into useful work during running, a mathematical model of the energetics of sprinting is constructed. This is used in conjunction with a careful analysis of Olympic records, in particular those obtained in the 1968 Games at Mexico City, to determine the magnitude of the rate of working against air resistance during running. It is established that times in the 100 m, 200 m and 400 m events at the Mexico Olympics were approximately 1.7% lower than they would otherwise have been if the races had been run at sea level. This information is used to deduce that the external work done per unit time against air resistance is about 7.5-9% of the total power output of a sprinter, running at maximum speed at sea level. These figures compare well with the value of 7.8% obtained independently by Davies (J. appl. Physiol 48, 702-709, 1980). The analysis provides evidence that a linear relation exists between running speed and the rate of degradation of mechanical energy into thermal energy up to the highest sprinting speeds attainable. The maximum power generated by a sprinter is approximately 3 kW.     

Effects of unilateral and bilateral plyometric training on power and jumping ability in women

Makaruk, H, Winchester, JB, Sadowski, J, Czaplicki, A, and Sacewicz, T. Effects of unilateral and bilateral plyometric training on power and jumping ability in women. J Strength Cond Res 25(12): 3311-3318, 2011-The purpose of this study was to examine the effects of unilateral and bilateral plyometric exercise on peak power and jumping performance during different stages of a 12-week training and detraining in women. Forty-nine untrained but physically active female college students were randomly assigned to 1 of 3 groups: unilateral plyometric group (n = 16), bilateral plyometric group (BLE; n = 18), and a control group (n = 15). Peak power and jumping ability were assessed by means of the alternate leg tests (10-second Wingate test and 5 alternate leg bounds), bilateral leg test (countermovement jump [CMJ]) and unilateral leg test (unilateral CMJ). Performance indicators were measured pretraining, midtraining, posttraining, and detraining. Differences between dependent variables were assessed with a 3 × 4 (group × time) repeated analysis of variance with Tukey's post hoc test applied where appropriate. Effect size was calculated to determine the magnitude of significant differences between the researched parameters. Only the unilateral plyometric training produced significant (p < 0.05) improvement in all tests from pretraining to midtraining, but there was no significant (p < 0.05) increase in performance indicators from midtraining to posttraining. The BLE group significantly (p < 0.05) improved in all tests from pretraining to posttraining and did not significantly (p > 0.05) decrease power and jumping ability in all tests during detraining. These results suggest that unilateral plyometric exercises produce power and jumping performance during a shorter period when compared to bilateral plyometric exercises but achieved performance gains last longer after bilateral plyometric training. Practitioners should consider the inclusion of both unilateral and bilateral modes of plyometric exercise to elicit rapid improvements and guard against detraining.     

Vertical jumping performance of bonobo (Pan paniscus) suggests superior muscle properties

Vertical jumping was used to assess muscle mechanical output in bonobos and comparisons were drawn to human jumping. Jump height, defined as the vertical displacement of the body centre of mass during the airborne phase, was determined for three bonobos of varying age and sex. All bonobos reached jump heights above 0.7 m, which greatly exceeds typical human maximal performance (0.3-0.4m). Jumps by one male bonobo (34 kg) and one human male (61.5 kg) were analysed using an inverse dynamics approach. Despite the difference in size, the mechanical output delivered by the bonobo and the human jumper during the push-off was similar: about 450 J, with a peak power output close to 3000 W. In the bonobo, most of the mechanical output was generated at the hips. To account for the mechanical output, the muscles actuating the bonobo's hips (directly and indirectly) must deliver muscle-mass-specific power and work output of 615 Wkg-1 and 92 Jkg-1, respectively. This was twice the output expected on the basis of muscle mass specific work and power in other jumping animals but seems physiologically possible. We suggest that the difference is due to a higher specific force (force per unit of cross-sectional area) in the bonobo.     

Are there any differences in power performance and morphological characteristics of Croatian adolescent soccer players according to the team position?

The aim of the study was to analyze differences in power performance and morphological characteristics of young Croatian soccer players with respect to their team positions and to establish correlations between the power performance variables. Anthropometric characteristics and jumping and sprint performances were analyzed for 45 soccer players (age 14-15; mean body height 175.4 +/- 6.61 cm; body weight 63.6 +/- 8.06 kg) according to their team positions (defender, midfielder, forward). Pearsons coefficient of correlation was used to determine the relationship between the power performance variables. There were no significant differences (p > 0.05) in the power performance of players according to their team position. The only significant differences between players were in some of the anthropometric characteristics, such as height and weight linear relationship was determined between almost all the power performance variables. Since the players in this study were very young and their sports careers have not reached their peak performance, it is possible that their nominal team positions may change during their soccer careers.     

Relationship between the 30-second wingate test and characteristics of isometric and explosive leg strength in young subjects

The aim of this study was to investigate a possible relation between power performance of the Wingate test (WT) and isometric leg strength (ILS) and explosive leg strength (ELS) characteristics in young men and women with different physical fitness levels. A total of 166 subjects, including 98 young men and 68 young women, were included in the study. The subjects were divided into a regular exercise group and a sedentary group. The physical and body mass index characteristics of the subjects were not different, and they had not taken part in the directed jumping. When the regular exercise and sedentary groups were considered together with men, women, and total population groups, no significant correlation existed between WT anaerobic fatigue index and ILS and ELS (p > 0.05), but significant positive correlations existed among peak power, peak power per weight, mean power, mean power per weight, and WT power, which were recorded in 5-second intervals (p < 0.001). Although the 5-second WT parameters were significantly correlated with ILS and ELS for the first 15-second period, this correlation was more pronounced for the last 15 seconds for all groups (p < 0.01). As a result, this study indicated that regular physical activity has a positive significant relation on WT power, ILS, and ELS in both sedentary men and women and those engaged in regular sports activities.