Faster top running speeds are achieved with greater ground forces not more rapid leg movements

The biomechanics of the fastest sprinter with a unilateral transtibial amputation

People have debated whether athletes with transtibial amputations should compete with nonamputees in track events despite insufficient information regarding how the use of running-specific prostheses (RSPs) affect athletic performance. Thus, we sought to quantify the spatiotemporal variables, ground reaction forces, and spring-mass mechanics of the fastest athlete with a unilateral transtibial amputation using an RSP to reveal how he adapts his biomechanics to achieve elite running speeds. Accordingly, we measured ground reaction forces during treadmill running trials spanning 2.87 to 11.55 m/s of the current male International Paralympic Committee T44 100- and 200-m world record holder. To achieve faster running speeds, the present study’s athlete increased his affected leg (AL) step lengths ( P < 0.001) through longer contact lengths ( P < 0.001) and his unaffected leg (UL) step lengths ( P < 0.001) through longer contact lengths ( P < 0.001) and greater stance average vertical ground reaction forces ( P < 0.001). At faster running speeds, step time decreased for both legs ( P < 0.001) through shorter ground contact and aerial times ( P < 0.001). Unlike athletes with unilateral transtibial amputations, this athlete maintained constant AL and UL stiffness across running speeds ( P ≥ 0.569). Across speeds, AL step lengths were 8% longer ( P < 0.001) despite 16% lower AL stance average vertical ground reaction forces compared with the UL ( P < 0.001). The present study’s athlete exhibited biomechanics that differed from those of athletes with bilateral and without transtibial amputations. Overall, we present the biomechanics of the fastest athlete with a unilateral transtibial amputation, providing insight into the functional abilities of athletes with transtibial amputations using running-specific prostheses.

NEW & NOTEWORTHY The present study’s athlete achieved the fastest treadmill running trial ever attained by an individual with a leg amputation (11.55 m/s). From 2.87 to 11.55 m/s, the present study’s athlete maintained constant affected and unaffected leg stiffness, which is atypical for athletes with unilateral transtibial amputations. Furthermore, the asymmetric vertical ground reaction forces of athletes with unilateral transtibial amputations during running may be the result of leg length discrepancies.

The Use of an Optical Measurement System to Monitor Sports Performance

The purpose of this study was to compare ground contact time between an optical measurement system and a force platform. Participants in this study included six collegiate level athletes who performed drop jumps and sprint strike steps for a total of 15 repetitions each. Ground contact data was simultaneously collected from an optical measurement system and a force platform, at a sampling frequency of 1000 Hz. Data was then analyzed with Pearson’s correlation and paired sample t-tests. The measures from the optical measurement system were found to be significantly higher (p < 0.001) than measures from the force platform in both conditions. Although significantly different, the extremely large relationships (0.979, 0.993) found between the two devices suggest the optical sensor is able to detect similar changes in performance to that of a force platform. Practitioners may continue to utilize optical sensors to monitor performance as it may provide a superior user-friendly alternative to more traditional based monitoring procedures, but must comprehend the inherent limitations due to the design of the optical sensors.

Associations Between Individual Lower-Limb Muscle Volumes and 100-m Sprint Time in Male Sprinters

PURPOSE

To elucidate the relationship between the muscularity of individual lower-limb muscles and 100-m-race time (t₁₀₀) in young-adult male sprinters.

METHODS

Thirty-one young-adult male sprinters took part in this study (age 19.9 ± 1.4 y, height 173.5 ± 4.6 cm, body mass 67.0 ± 4.9 kg, t₁₀₀ 10.23-11.71 s). Cross-sectional images from the origin to insertion of 12 lower-limb muscles were obtained with via magnetic resonance imaging (MRI). The absolute volume of each muscle, the ratio of total volume of measured muscles to body mass, the ratio of individual muscle volume to body mass, and the ratio between 2 individual muscle volumes were calculated as indices of muscularity using the images. A stepwise multiple-regression analysis was performed to examine the association between the indices and t₁₀₀.

RESULTS

A stepwise multiple-regression analysis produced an equation (adjusted R² = .234) with the gluteus maximus-to-quadriceps femoris muscle-volume ratio (β = -0.509, P = .003) as the explanatory variable.

CONCLUSIONS

Individual differences in 100-m-race performance cannot be explained by the muscularity of specific muscles, and 23% of the variability in the performance can be explained by the relative difference between the muscularity of gluteus maximus and quadriceps femoris; faster runners have a greater gluteus maximus relative to quadriceps femoris.

Hip Flexor and Knee Extensor Muscularity Are Associated With Sprint Performance in Sprint-Trained Preadolescent Boys

PURPOSE

We attempted to determine the relationships between the cross-sectional area (CSA) of the trunk and lower limb muscles and sprint performance in male preadolescent sprinters.

METHODS

Fifteen sprint-trained preadolescent boys (age 11.6 ± 0.4 y) participated in this study. The CSAs of the participants' trunk and lower limb muscles were measured using magnetic resonance imaging, and these muscles were normalized with free-fat mass. To assess participants' sprint performance, sprint time and variables during the 50-m sprint test were measured. The sprint variables were expressed as their indices by normalizing with body height.

RESULTS

The relative CSAs of psoas major, adductors, and quadriceps femoris were significantly correlated with sprint time (r = -.802, -.643, and -.639). Moreover, the relative CSAs of these muscles were significantly correlated with indices of sprint velocity (r = .694, .612, and .630) and step frequency (r = .687, .740, and .590) but not with that of step length.

CONCLUSIONS

These findings suggest that greater hip flexor and knee extensor muscularity in male preadolescent sprinters may help achieve superior sprint performance by potentially enhancing their moments, which may be induced by increased step frequency rather than step length during sprinting.

The effect of altering loading distance on skeleton start performance: Is higher pre-load velocity always beneficial?

Athletes initiating skeleton runs differ in the number of steps taken before loading the sled. We aimed to understand how experimentally modifying loading distance influenced sled velocity and overall start performance. Ten athletes (five elite, five talent; 67% of all national athletes) underwent two to four sessions, consisting of two dry-land push-starts in each of three conditions (preferred, long and short loading distances). A magnet encoder on the sled wheel provided velocity profiles and the overall performance measure (sled acceleration index). Longer pre-load distances (12% average increase from preferred to long distances) were related to higher pre-load velocity (r = 0.94), but lower load effectiveness (r = -0.75; average reduction 29%). Performance evaluations across conditions revealed that elite athletes' preferred distance push-starts were typically superior to the other conditions. Short loading distances were generally detrimental, whereas pushing the sled further improved some talent-squad athletes' performance. Thus, an important trade-off between generating high pre-load velocity and loading effectively was revealed, which coaches should consider when encouraging athletes to load later. This novel intervention study conducted within a real-world training setting has demonstrated the scope to enhance push-start performance by altering loading distance, particularly in developing athletes with less extensive training experience.

Positive Effects of Augmented Feedback to Reduce Time on Ground in Well-Trained Runners

CONTEXT

Successful elite sprint to long-distance runners are known to have shorter ground-contact time (GCT) than their less successful counterparts.

PURPOSE

To investigate whether augmented feedback (aF) about GCT can reduce the time on ground (TOG) per minute in long-distance runners and, if so, whether this reduction improves running performance.

METHODS

Thirty well-trained runners were allocated to 3 groups. The intervention group (IG) received visual aF about their GCT during 8 high-intensity interval sessions in the 4-wk training period and were instructed to minimize GCT. The 1st control group (CG1) trained with the IG but was not given any feedback. The 2nd control group (CG2) followed their own training routine. Data were obtained pre- and postintervention for all 3 groups. The dependent variable was TOG per minute, computed from step frequency and GCT.

RESULTS

The IG significantly reduced TOG (P = .043, -1.7%, 90%CL -3.1;-0.3) and improved their mean 10 × 400-m performance time (P < .001, -1.5%, 90%CL -1.9;-1.1). In contrast, the 2 control groups revealed unchanged values, indicating that normal high-intensity training and an individualized routine without aF were not able to reduce TOG. The fact that CG1 received the same instructions and participated in the same training sessions as the IG underlined that aF was crucial to reduce TOG.

CONCLUSIONS

The provision of aF about GCT seems to be a promising approach that should be considered during training practice of well-trained runners.

Surface friction alters the agility of a small Australian marsupial

Movement speed can underpin an animal's probability of success in ecological tasks. Prey often use agility to outmanoeuvre predators, however faster speeds increase inertia and reduce agility. Agility is also constrained by grip, as the foot must have sufficient friction with the ground to apply the forces required for turning. Consequently, ground surface should affect optimum turning speed. We tested the speed-agility trade-off in buff-footed antechinus (Antechinus mysticus) on two different surfaces. Antechinus used slower turning speeds over smaller turning radii on both surfaces, as predicted by the speed-agility trade-off. Slipping was 64% more likely on the low-friction surface, and had a higher probability of occurring the faster the antechinus were running before the turn. However, antechinus compensated for differences in surface friction by using slower pre-turn speeds as their amount of experience on the low-friction surface increased, which consequently reduced their probability of slipping. Conversely, on the high-friction surface, antechinus used faster pre-turn speeds in later trials, which had no effect on their probability of slipping. Overall, antechinus used larger turning radii (0.733 ± 0.062 vs 0.576 ± 0.051 m) and slower pre-turn (1.595 ± 0.058 vs 2.174 ± 0.050 ms-1) and turning speeds (1.649 ± 0.061 vs 2.01 ± 0.054 ms-1) on the low-friction surface. Our results demonstrate the interactive effect of surface friction and the speed-agility trade-off on speed choice. To predict wild animals’ movement speeds, future studies should examine the interactions between biomechanical trade-offs and terrain, and quantify the costs of motor mistakes in different ecological activities.

Contraction speed and type influences rapid utilisation of available muscle force: neural and contractile mechanisms

This study investigated the influence of contraction speed and type on the human ability to rapidly increase torque and utilise the available maximum voluntary torque (MVT) as well as the neuromuscular mechanisms underpinning any effects. Fifteen young, healthy males completed explosive-voluntary knee-extensions in five conditions: isometric (ISO), and both concentric and eccentric at two constant accelerations of 500°.s−2 (CONSLOW and ECCSLOW) and 2000°.s−2 (CONFAST and ECCFAST). Explosive torque and quadriceps EMG were recorded every 25 ms up to 150 ms from their respective onsets and normalised to the available MVT and EMG at MVT, respectively, specific to that joint angle and velocity. Neural efficacy (explosive Voluntary:Evoked octet torque) was also measured, and torque data were entered into a Hill-type muscle model to estimate muscle performance. Explosive torques normalised to MVT (and normalised muscle forces) were greatest in the concentric, followed by isometric, and eccentric conditions; and in the fast compared with slow speeds within the same contraction type (CONFAST&gt;CONSLOW&gt;ISO, and ECCFAST&gt;ECCSLOW). Normalised explosive-phase EMG and neural efficacy were greatest in concentric, followed by isometric and eccentric conditions, but were similar for fast and slow contractions of the same type. Thus, distinct neuromuscular activation appeared to explain the effect of contraction type but not speed on normalised explosive torque, suggesting the speed effect is an intrinsic contractile property. These results provide novel evidence that the ability to rapidly increase torque/force and utilise the available MVT is influenced by both contraction type and speed, due to neural and contractile mechanisms, respectively.

Mixed Training Methods: Effects of Combining Resisted Sprints or Plyometrics with Optimum Power Loads on Sprint and Agility Performance in Professional Soccer Players

The aim of this study was to compare the effects of two different mixed training programs (optimum power load [OPL] + resisted sprints [RS] and OPL + vertical/horizontal plyometrics [PL]) on neuromuscular performance of elite soccer players during a short-term training preseason. Eighteen male professional soccer players took part in this study. The athletes were pair-matched in two training groups: OPL + RS and OPL + PL. Unloaded and resisted sprinting speeds at 5-, 10-, 20-, and 30-m, change of direction (COD) speed, and performance in the squat jump (SJ), countermovement jump (CMJ), and horizontal jump (HJ) were assessed pre- and post- a 5-week training period. Magnitude based inference with the effect sizes were used for data analysis. A possible increase in the SJ and CMJ heights and a likely increase in the HJ distance were observed in the OPL + PL group. Meaningful improvements were observed in the COD speed test for both training groups comparing pre- and post-measures. In both unloaded and resisted sprints, meaningful decreases were observed in the sprinting times for all distances tested. This study shows that a mixed training approach which comprises exercises and workloads able to produce positive adaptations in different phases of sprinting can be a very effective strategy in professional soccer players. Moreover, the possibility of combining optimum power loads with resisted sprints and plyometrics emerges as a novel and suitable option for coaches and sport scientists, due to the applicability and efficiency of this strength-power training approach.

Ground Reaction Forces During Sprinting in Unilateral Transfemoral Amputees

Understanding the characteristics of ground reaction forces (GRFs) on both limbs during sprinting in unilateral amputees wearing running-specific prostheses would provide important information that could be utilized in the evaluation of athletic performance and development of training methods in this population. The purpose of this study was to compare GRFs between intact and prosthetic limbs during sprinting in unilateral transfemoral amputees wearing running-specific prostheses. Nine sprinters with unilateral transfemoral amputation wearing the same type of prosthesis performed maximal sprinting on a 40-m runway. GRFs were recorded from 7 force plates placed in the center of the runway. Peak forces and impulses of the GRFs in each direction were compared between limbs. Peak forces in vertical, braking, propulsive, and medial directions were significantly greater in intact limbs than those in prosthetic limbs, whereas there were no significant differences in peak lateral force between limbs. Further, significantly less braking impulses were observed in prosthetic limbs than in intact limbs; however, the other measured impulses were not different between limbs. Therefore, the results of the present study suggest that limb-specific rehabilitation and training strategies should be developed for transfemoral amputees wearing running-specific prostheses.

Elite long jumpers with below the knee prostheses approach the board slower, but take-off more effectively than non-amputee athletes

The use of technological aids to improve sport performance ('techno doping') and inclusion of Paralympic athletes in Olympic events are matters of ongoing debate. Recently, a long jumper with a below the knee amputation (BKA) achieved jump distances similar to world-class athletes without amputations, using a carbon fibre running-specific prosthesis (RSP). We show that athletes with BKA utilize a different, more effective take-off technique in the long jump, which provided the best athlete with BKA a performance advantage of at least 0.13 m compared to non-amputee athletes. A maximum speed constraint imposed by the use of RSPs would indicate a performance disadvantage for the long jump. We found slower maximum sprinting speeds in athletes with BKA, but did not find a difference in the overall vertical force from both legs of athletes with BKA compared to non-amputees. Slower speeds might originate from intrinsically lower sprinting abilities of athletes with BKA or from more complex adaptions in sprinting mechanics due to the biomechanical and morphological differences induced by RSPs. Our results suggest that due to different movement strategies, athletes with and without BKA should likely compete in separate categories for the long jump.

Leg amputation side determines performance in curve sprinting: a case study on a Paralympic medalist

The lower limb kinetics of curve sprinting in amputees are not well described in the literature, particularly with respect to the effect of the side of amputation. This is an issue due to the importance of the knowledge for prosthetic design and classification of athletes. Thus, the aim of this study was to investigate the influence of side of amputation on curve sprinting performance in athletes with a unilateral leg amputation. A three-dimensional motion analysis system (Vicon), four force plates (Kistler) and a modified mathematical human model (ALASKA) were used to compare clockwise and counter clockwise curve sprinting lower limb kinematics and kinetics of a Paralympic medalist with a left-sided knee exarticular amputation. Results reveal that vertical ground reaction force application and total vertical impulse were lower when the affected limb was at the inside of the curve. The unaffected limb showed joint mechanics different to those established for non-amputee athletes and might contribute better to propulsion when being the inside limb. Curve sprinting biomechanics and the ability to attain high radial velocities are directly dependent on the side of amputation relative to the curve direction in a unilateral amputee athlete of highest performance level.

Developing a Low-Cost Force Treadmill via Dynamic Modeling

By incorporating force transducers into treadmills, force platform-instrumented treadmills (commonly called force treadmills) can collect large amounts of gait data and enable the ground reaction force (GRF) to be calculated. However, the high cost of force treadmills has limited their adoption. This paper proposes a low-cost force treadmill system with force sensors installed underneath a standard exercise treadmill. It identifies and compensates for the force transmission dynamics from the actual GRF applied on the treadmill track surface to the force transmitted to the force sensors underneath the treadmill body. This study also proposes a testing procedure to assess the GRF measurement accuracy of force treadmills. Using this procedure in estimating the GRF of “walk-on-the-spot motion,” it was found that the total harmonic distortion of the tested force treadmill system was about 1.69%, demonstrating the effectiveness of the approach.

Optimal stride frequencies in running at different speeds

During running at a constant speed, the optimal stride frequency (SF) can be derived from the u-shaped relationship between SF and heart rate (HR). Changing SF towards the optimum of this relationship is beneficial for energy expenditure and may positively change biomechanics of running. In the current study, the effects of speed on the optimal SF and the nature of the u-shaped relation were empirically tested using Generalized Estimating Equations. To this end, HR was recorded from twelve healthy (4 males, 8 females) inexperienced runners, who completed runs at three speeds. The three speeds were 90%, 100% and 110% of self-selected speed. A self-selected SF (SFself) was determined for each of the speeds prior to the speed series. The speed series started with a free-chosen SF condition, followed by five imposed SF conditions (SFself, 70, 80, 90, 100 strides·min-1) assigned in random order. The conditions lasted 3 minutes with 2.5 minutes of walking in between. SFself increased significantly (p<0.05) with speed with averages of 77, 79, 80 strides·min-1 at 2.4, 2.6, 2.9 m·s-1, respectively). As expected, the relation between SF and HR could be described by a parabolic curve for all speeds. Speed did not significantly affect the curvature, nor did it affect optimal SF. We conclude that over the speed range tested, inexperienced runners may not need to adapt their SF to running speed. However, since SFself were lower than the SFopt of 83 strides·min-1, the runners could reduce HR by increasing their SFself.

Double-Poling Biomechanics of Elite Cross-country Skiers: Flat versus Uphill Terrain

INTRODUCTION

In light of the recent revolutionary change in the use of the double-poling (DP) technique in cross-country skiing, our purpose was to compare the associated kinetics and kinematics on flat (DPflat) and uphill terrain (DPup), as well as to identify factors that determine performance.

METHODS

Thirteen elite male cross-country skiers completed two incremental speed tests (Vpeak) involving roller skiing with the DP technique at moderate (13 and 24 km·h) and high speed (15 and 28.5 km·h) on a treadmill that was flat (1°) or tilted uphill (7°). Pole forces and three-dimensional whole-body kinematics were monitored simultaneously.

RESULTS

In comparison to DPflat, during DPup, swing times were much shorter (-48%) and peak pole forces greater (+13%) and generated later during the poling phase (+68%), with higher impulses for all force components (+87%-123%). Furthermore, pole forces were 18% more effectively oriented for propulsion. During DPup, the skiers demonstrated more flexed elbows, as well as shoulder angles that were less flexed in the forward direction and less abducted throughout the poling phase, together with more highly flexed knee and ankle joints, a more upright thorax, less flexed hips, and a shortened backward swing after pole off. With DPup, the skiers raised their center of mass 25% more, attaining maximal heel raise and maximal vertical position at a timepoint closer to pole plant compared with flat. On the uphill incline, the magnitude of Vpeak was positively related to body mass, relative pole length (% body height), and magnitude of heel raise.

CONCLUSIONS

The present findings provide novel insights into the coordination, kinetics and kinematics of elite skiers while DP on flat and uphill terrain.

Relationships between Isometric Force-Time Characteristics and Dynamic Performance

The purpose of this study was to explore the relationships between isometric mid-thigh pull (IMTP) force-time characteristics (peak force and time-specific force vales (100⁻250 ms)) and dynamic performance and compare dynamic performance between stronger and weaker athletes. Forty-three athletes from different sports (rowing, soccer, bicycle motocross, and hockey) performed three trials of the squat jump (SJ), countermovement jump (CMJ), and IMTP, and performed a one repetition maximum power clean (PC). Reactive strength index modified (RSImod) was also calculated from the CMJ. Statistically significant large correlations between IMTP force-time characteristics and PC (ρ = 0.569⁻0.674, p < 0.001), and moderate correlations between IMTP force-time characteristics (excluding force at 100 ms) and RSImod (ρ = 0.389⁻0.449, p = 0.013⁻0.050) were observed. Only force at 250 ms demonstrated a statistically significant moderate correlation with CMJ height (ρ = 0.346, p = 0.016) and no statistically significant associations were observed between IMTP force-time characteristics and SJ height. Stronger athletes (top 10) demonstrated statistically significantly greater CMJ heights, RSImods, and PCs (p ≤ 0.004, g = 1.32⁻1.89) compared to weaker (bottom 10) athletes, but no differences in SJ height were observed (p = 0.871, g = 0.06). These findings highlight that the ability to apply rapidly high levels of force in short time intervals is integral for PC, CMJ height, and reactive strength.

The Influence of Maturation on Sprint Performance in Boys over a 21-Month Period

PURPOSE

This study examined how the characteristics of maximal overground sprint performance are affected by the period of peak height velocity (PHV) in boys.

METHODS

One hundred eighty-nine school-age boys completed two assessments of maximal sprint performance, separated by a 21-month period. Kinematic characteristics of sprint performance were collected during a 30-m sprint using a floor-level optical measurement system, with modeled force and stiffness characteristics also calculated. Participants were grouped according to maturation using a noninvasive predictive equation. Individuals whose maturity offset was <-0.5 yr in both assessments were classed as "pre-PHV" (n = 67), whereas those whose maturity offset developed from <-0.5 to >0.5 yr in test two were classed as "pre-to-post PHV" (n = 39). Participants with a maturity offset between >-0.5 and <0.5 yr at test 2 were removed from analysis (n = 67) to ensure that the entire pre-to-post-PHV group had experienced the PHV spurt.

RESULTS

The pre-to-post-PHV group experienced significantly greater increases in speed (10.4% vs 5.6%) and relative vertical stiffness (12.1% vs 5.6%) compared with the pre-PHV group. Step frequency declined (-2.4%) and contact time increased (2.3%) in the pre-PHV group, whereas step frequency increased (2.7%) and contact time decreased (-3.6%) in the pre-PHV to post-PHV group. Changes in relative measures of vertical stiffness, maximal force, and leg stiffness accounted for 79% and 83% of the changes in speed between assessments for pre-PHV and pre-to-post-PHV groups, respectively.

CONCLUSIONS

As boys experience PHV, there are greater increases in maximal sprint speed compared with those who remain pre-PHV. Furthermore, measures of relative stiffness and relative maximal force appear to exert an important influence on the development of maximal sprint speed in boys, regardless of maturity.

Long-Term Changes in Jump Performance and Maximum Strength in a Cohort of National Collegiate Athletic Association Division I Women's Volleyball Athletes

Kavanaugh, AA, Mizuguchi, S, Sands, WA, Ramsey, MW, and Stone, MH. Long-term changes in jump performance and maximum strength in a cohort of NCAA division I women's volleyball Athletes. J Strength Cond Res 32(1): 66-75, 2018-The purpose of this investigation was to quantify the magnitude of change in maximal strength and jumping abilities over approximately 1, 2, and 3 years of supervised sport and resistance training in National Collegiate Athletic Association (NCAA) division I women's volleyball athletes. This was an exploratory study on a cohort of women's volleyball athletes (n = 29) split into 3 groups based on the length of the time spent in a supervised resistance training program: group 1 (n = 11): 0.7 ± 0.3 years, group 2 (n = 9): 1.6 ± 0.2 years, and group 3 (n = 9): 2.4 ± 0.6 years. Monitoring tests consisted of standing height (cm), body mass (kg), body fat (%), static jump height (SJH) and countermovement JH (CMJH) with 0-, 11-, and 20-kg loads (cm), and midthigh clean pull isometric peak force (IPF) and allometrically scaled IPF (IPFa) (N·kg). Increasing trends were observed for all variables from groups 1 to 2 to 3. Statistically greater improvements (p ≤ 0.05) with moderate to large effect sizes were found between groups 1 and 3 for SJH 0 (19.7%, d = 1.35), SJH 11 (23.8%, d = 1.23), SJH 20 (30.6%, d = 1.20), CMJH 11 (22.6%, d = 1.18), IPF (44.4%, d = 1.22), and IPFa (41.2%, d = 1.32). A combination of traditional resistance training exercises and weightlifting variations at various loads, in addition to volleyball practice, seem to be effective at increasing maximal strength by 44% and vertical JH by 20-30% in NCAA division I women's volleyball athletes after about 2.5 years of training. Furthermore, these characteristics can be improved in the absence of additional plyometric training outside normal volleyball-specific practice.

How do prosthetic stiffness, height and running speed affect the biomechanics of athletes with bilateral transtibial amputations?

Limited available information describes how running-specific prostheses and running speed affect the biomechanics of athletes with bilateral transtibial amputations. Accordingly, we quantified the effects of prosthetic stiffness, height and speed on the biomechanics of five athletes with bilateral transtibial amputations during treadmill running. Each athlete performed a set of running trials with 15 different prosthetic model, stiffness and height combinations. Each set of trials began with the athlete running on a force-measuring treadmill at 3 m s^-1, subsequent trials incremented by 1 m s^-1 until they achieved their fastest attainable speed. We collected ground reaction forces (GRFs) during each trial. Prosthetic stiffness, height and running speed each affected biomechanics. Specifically, with stiffer prostheses, athletes exhibited greater peak and stance average vertical GRFs (β = 0.03; p < 0.001), increased overall leg stiffness (β = 0.21; p < 0.001), decreased ground contact time (β = -0.07; p < 0.001) and increased step frequency (β = 0.042; p < 0.001). Prosthetic height inversely associated with step frequency (β = -0.021; p < 0.001). Running speed inversely associated with leg stiffness (β = -0.58; p < 0.001). Moreover, at faster running speeds, the effect of prosthetic stiffness and height on biomechanics was mitigated and unchanged, respectively. Thus, prosthetic stiffness, but not height, likely influences distance running performance more than sprinting performance for athletes with bilateral transtibial amputations.

The Importance of Muscular Strength in Athletic Performance

This review discusses previous literature that has examined the influence of muscular strength on various factors associated with athletic performance and the benefits of achieving greater muscular strength. Greater muscular strength is strongly associated with improved force-time characteristics that contribute to an athlete's overall performance. Much research supports the notion that greater muscular strength can enhance the ability to perform general sport skills such as jumping, sprinting, and change of direction tasks. Further research indicates that stronger athletes produce superior performances during sport specific tasks. Greater muscular strength allows an individual to potentiate earlier and to a greater extent, but also decreases the risk of injury. Sport scientists and practitioners may monitor an individual's strength characteristics using isometric, dynamic, and reactive strength tests and variables. Relative strength may be classified into strength deficit, strength association, or strength reserve phases. The phase an individual falls into may directly affect their level of performance or training emphasis. Based on the extant literature, it appears that there may be no substitute for greater muscular strength when it comes to improving an individual's performance across a wide range of both general and sport specific skills while simultaneously reducing their risk of injury when performing these skills. Therefore, sport scientists and practitioners should implement long-term training strategies that promote the greatest muscular strength within the required context of each sport/event. Future research should examine how force-time characteristics, general and specific sport skills, potentiation ability, and injury rates change as individuals transition from certain standards or the suggested phases of strength to another.

Alteration of swing leg work and power during human accelerated sprinting

This study investigated changes in lower-extremity joint work and power during the swing phase in a maximal accelerated sprinting. Twelve male sprinters performed 60 m maximal sprints while motion data was recorded. Lower-extremity joint work and power during the swing phase of each stride for both legs were calculated. Positive hip and negative knee work (≈4.3 and ≈−2.9 J kg⁻¹) and mean power (≈13.4 and ≈−8.7 W kg⁻¹) during the entire swing phase stabilized or decreased after the 26.2±1.1 (9.69±0.25 m s⁻¹) or 34.3±1.5 m mark (9.97±0.26 m s⁻¹) during the acceleration phase. In contrast, the hip negative work and mean power during the early swing phase (≈7-fold and ≈3.7-fold increase in total), as well as the knee negative work and power during the terminal swing phase (≈1.85-fold and ≈2-fold increase in total), increased until maximal speed. Moreover, only the magnitudes of increases in negative work and mean power at hip and knee joints during the swing phase were positively associated with the increment of running speed from the middle of acceleration phase. These findings indicate that the roles of energy generation and absorption at the hip and knee joints shift around the middle of the acceleration phase as energy generation and absorption at the hip during the late swing phase and at the knee during early swing phase are generally maintained or decreased, and negative work and power at hip during the early swing phase and at knee during the terminal swing phase may be responsible for increasing running speed when approaching maximal speed.

Summary: The roles of respective swing leg joints intricately change with increases in running speed during accelerated sprinting.

Vertical- vs. Horizontal-Oriented Drop Jump Training: Chronic Effects on Explosive Performances of Elite Handball Players

Dello Iacono, A, Martone, D, Milic, M, and Padulo, J. Vertical- vs. horizontal-oriented drop jump training: chronic effects on explosive performances of elite handball players. J Strength Cond Res 31(4): 921-931, 2017-This study aimed to assess the chronic effects of vertical drop jump (VDJ)- and horizontal drop jump (HDJ)-based protocols on neuromuscular explosive abilities, such as jumping, sprinting, and changes of direction (COD). Eighteen elite male handball players (age 23.4 ± 4.6 years, height 192.5 ± 3.7 cm, weight 87.8 ± 7.4 kg) were assigned to either VDJ or HDJ group training twice a week for 10 weeks. Participants performed 5-8 sets × 6-10 repetitions of vertical alternate (VDJ) or horizontal alternate (HDJ) 1-leg drop jumps, landing from the top of a platform 25 cm in height. Before and after training, several performance, kinetic, and kinematic variables were assessed. The HDJ led to greater improvement of the sprint time (-8.5% vs. -4%, p ≤ 0.05) and COD performance in comparison with the VDJ (-7.9% vs. -1.1%, p ≤ 0.05), whereas the VDJ caused greater improvement in the vertical jump compared with the HDJ (+8.6% vs. +4.1%, p ≤ 0.05). Moreover, the VDJ regimen compared with the HDJ induced greater changes in the kinetic variables associated with vertical jumping performance, such as peak ground reaction forces (+10.3% vs. +4.3%), relative impulse (+12.4% vs. +5.7%), leg spring stiffness (+17.6% vs. +4.6%), contact time (CT) (-10.1% vs. -1.5%), and reactive strength index (+7.2% vs. +2.1%); all comparisons with p ≤ 0.05. Conversely, the HDJ regimen was able to improve the short-distance and COD performances by increasing the step length (+3.5% vs. +1.5% with p ≤ 0.05) and reducing the CT on COD (-12.1% vs. -2.1% with p ≤ 0.05) more than the VDJ. This investigation showed the crucial role that specific plyometric regimens play in optimizing similar biomechanical featured functional performances, such as jumping, sprinting, and COD.

Maximum-speed curve-running biomechanics of sprinters with and without unilateral leg amputations

On curves, non-amputees' maximum running speed is slower on smaller radii and thought to be limited by the inside leg's mechanics. Similar speed decreases would be expected for non-amputees in both counterclockwise and clockwise directions because they have symmetric legs. However, sprinters with unilateral leg amputation have asymmetric legs, which may differentially affect curve-running performance and Paralympic competitions. To investigate this and understand the biomechanical basis of curve running, we compared maximum curve-running (radius 17.2 m) performance and stride kinematics of six non-amputee sprinters and 11 sprinters with a transtibial amputation. Subjects performed randomized, counterbalanced trials: two straight, two counterclockwise curves and two clockwise curves. Non-amputees and sprinters with an amputation all ran slower on curves compared with straight running, but with different kinematics. Non-amputees ran 1.9% slower clockwise compared with counterclockwise (P<0.05). Sprinters with an amputation ran 3.9% slower with their affected leg on the inside compared with the outside of the curve (P<0.05). Non-amputees reduced stride length and frequency in both curve directions compared with straight running. Sprinters with an amputation also reduced stride length in both curve-running directions, but reduced stride frequency only on curves with the affected leg on the inside. During curve running, non-amputees and athletes with an amputation had longer contact times with their inside compared with their outside leg, suggesting that the inside leg limits performance. For sprinters with an amputation, the prolonged contact times of the affected versus unaffected leg seem to limit maximum running speed during both straight running and running on curves with the affected leg on the inside.

Characterisation of the responsive properties of two running-specific prosthetic models

BACKGROUND

The need for information regarding running-specific prosthetic properties has previously been voiced. Such information is necessary to assist in athletes' prostheses selection.

OBJECTIVES

This study aimed to describe the characteristics of two commercially available running-specific prostheses.

STUDY DESIGN

The running-specific prostheses were tested (in an experimental setup) without the external interference of athlete performance variations.

METHODS

Four stiffness categories of each running-specific prosthetic model (Xtend^™ and Xtreme^™) were tested at seven alignment setups and three drop masses (28, 38 and 48 kg). Results for peak ground reaction force (GRF_peak), contact time ( t_c), flight time ( t_f), reactive strength index (RSI) and maximal compression (Δ L) were determined during controlled dropping of running-specific prostheses onto a force platform with different masses attached to the experimental setup.

RESULTS

No statistically significant differences were found between the different setups of the running-specific prostheses. Statistically significant differences were found between the two models for all outcome variables (GRF_peak, Xtend > Xtreme; t_c, Xtreme > Xtend; t_f, Xtreme > Xtend; RSI, Xtend > Xtreme; Δ L, Xtreme > Xtend; p < 0.05).

CONCLUSION

These findings suggest that the Xtreme stores more elastic energy than the Xtend, leading to a greater performance response. The specific responsive features of blades could guide sprint athletes in their choice of running-specific prostheses. Clinical relevance Insights into the running-specific prosthesis (RSP) properties and an understanding of its responsive characteristics have implications for athletes' prosthetic choice. Physiologically and metabolically, a short sprint event (i.e. 100 m) places different demands on the athlete than a long sprint event (i.e. 400 m), and the RSP should match these performance demands.

Prosthetic model, but not stiffness or height, affects the metabolic cost of running for athletes with unilateral transtibial amputations

Running-specific prostheses enable athletes with lower limb amputations to run by emulating the spring-like function of biological legs. Current prosthetic stiffness and height recommendations aim to mitigate kinematic asymmetries for athletes with unilateral transtibial amputations. However, it is unclear how different prosthetic configurations influence the biomechanics and metabolic cost of running. Consequently, we investigated how prosthetic model, stiffness, and height affect the biomechanics and metabolic cost of running. Ten athletes with unilateral transtibial amputations each performed 15 running trials at 2.5 or 3.0 m/s while we measured ground reaction forces and metabolic rates. Athletes ran using three different prosthetic models with five different stiffness category and height combinations per model. Use of an Ottobock 1E90 Sprinter prosthesis reduced metabolic cost by 4.3 and 3.4% compared with use of Freedom Innovations Catapult [fixed effect (β) = -0.177; P < 0.001] and Össur Flex-Run (β = -0.139; P = 0.002) prostheses, respectively. Neither prosthetic stiffness (P ≥ 0.180) nor height (P = 0.062) affected the metabolic cost of running. The metabolic cost of running was related to lower peak (β = 0.649; P = 0.001) and stance average (β = 0.772; P = 0.018) vertical ground reaction forces, prolonged ground contact times (β = -4.349; P = 0.012), and decreased leg stiffness (β = 0.071; P < 0.001) averaged from both legs. Metabolic cost was reduced with more symmetric peak vertical ground reaction forces (β = 0.007; P = 0.003) but was unrelated to stride kinematic symmetry (P ≥ 0.636). Therefore, prosthetic recommendations based on symmetric stride kinematics do not necessarily minimize the metabolic cost of running. Instead, an optimal prosthetic model, which improves overall biomechanics, minimizes the metabolic cost of running for athletes with unilateral transtibial amputations.NEW & NOTEWORTHY The metabolic cost of running for athletes with unilateral transtibial amputations depends on prosthetic model and is associated with lower peak and stance average vertical ground reaction forces, longer contact times, and reduced leg stiffness. Metabolic cost is unrelated to prosthetic stiffness, height, and stride kinematic symmetry. Unlike nonamputees who decrease leg stiffness with increased in-series surface stiffness, biological limb stiffness for athletes with unilateral transtibial amputations is positively correlated with increased in-series (prosthetic) stiffness.

Skilful force control in expert pianists

Dexterous object manipulation in skilful behaviours such as surgery, craft making, and musical performance involves fast, precise, and efficient control of force with the fingers. A challenge in playing musical instruments is the requirement of independent control of the magnitude and rate of force production, which typically vary in relation to loudness and tempo. However, it is unknown how expert musicians skilfully control finger force to elicit tones with a wide range of loudness and tempi. Here, we addressed this issue by comparing the variation of spatiotemporal characteristics of force during repetitive and simultaneous piano keystrokes in relation to the loudness and tempo between pianists and musically untrained individuals. While the peak key-descending velocity varied with loudness but not with tempo in both groups, the peak and impulse of the key-depressing force were smaller in pianists than in the non-musicians, specifically when eliciting loud tones, suggesting superior energetic efficiency in the trained individuals. The key-depressing force was more consistent across strikes in pianists than in the non-musicians at all loudness levels but only at slow tempi, confirming expertise-dependency of precise force control. A regression analysis demonstrated that individual differences in the keystroke rates when playing at the fastest tempo across the trained pianists were negatively associated with the force impulse during the key depression but not with the peak force only at the loudest tone. This suggests that rapid reductions of force following the key depression plays a role in considerably fast performance of repetitive piano keystrokes.

Skeleton sled velocity profiles: a novel approach to understand critical aspects of the elite athletes' start phases

The development of velocity across the skeleton start is critical to performance, yet poorly understood. We aimed to understand which components of the sled velocity profile determine performance and how physical abilities influence these components. Thirteen well-trained skeleton athletes (>85% of athletes in the country) performed dry-land push-starts alongside countermovement jump and sprint tests at multiple time-points. A magnet encoder attached to the sled wheel provided velocity profiles, which were characterised using novel performance descriptors. Stepwise regression revealed four variables (pre-load velocity, pre-load distance, load effectiveness, velocity drop) to explain 99% variance in performance (β weights: 1.70, -0.81, 0.25, -0.07, respectively). Sprint times and jump ability were associated (r ± 90% CI) with pre-load velocity (-0.70 ± 0.27 and 0.88 ± 0.14, respectively) and distance (-0.48 ± 0.39 and 0.67 ± 0.29, respectively), however, unclear relationships between both physical measures and load effectiveness (0.33 ± 0.44 and -0.35 ± 0.48, respectively) were observed. Athletes should develop accelerative ability to attain higher velocity earlier on the track. Additionally, the loading phase should not be overlooked and may be more influenced by technique than physical factors. Future studies should utilise this novel approach when evaluating skeleton starts or interventions to enhance performance.

The knee extensor moment arm is associated with performance in male sprinters

PURPOSE

Although large knee extensor torque contributes to superior sprint performance, previous findings have indicated that the quadriceps cross-sectional area (CSA), a pivotal morphological regulator of knee extensor torque, is not correlated with performance in sprinters. We hypothesized that the knee extensor moment arm (MA), another main morphological regulator of knee extensor torque, may affect sprint performance. To test this hypothesis, we examined the relationship between knee extensor MA and sprint performance.

METHODS

The quadriceps CSA and knee extensor MA in 32 well-trained male sprinters and 32 male non-sprinters were measured using magnetic resonance imaging.

RESULTS

Knee extensor MA, but not quadriceps CSA, was greater in sprinters than in non-sprinters (P = 0.013). Moreover, knee extensor MA, but not the quadriceps CSA, was correlated with the personal best time in a 100-m race in sprinters (r = -0.614, P < 0.001). Furthermore, among 24 sprinters who participated in the 60-m sprint test, knee extensor MA was correlated with sprinting velocities in the acceleration (r = 0.717, P < 0.001) and maximum speed (r = 0.697, P < 0.001) phases.

CONCLUSION

The present study demonstrates that the knee extensor MA is greater in sprinters than in non-sprinters, and this morphological structure in sprinters is associated with sprint performance. Therefore, for the first time, we provided evidence that a greater knee extensor MA in sprinters may be an advantageous for achieving superior sprint performance.

Experience level influences the effect of attentional focus on sprint performance

Two experiments evaluated the influence of attentional focus on 10-meter sprint time and start kinetics in a group of collegiate soccer players and highly experienced sprinters. In Experiment 1, the collegiate soccer players were asked to perform 10-meter sprints under an external focus condition, an internal focus condition and a control condition. For the 10-meter sprint time, the results showed that both the external focus and control conditions resulted in significantly faster sprint times than the internal focus condition. There were no significant differences observed between the external focus and control conditions. There were also no significant differences observed across any of the conditions for a select set of kinetic variables. In Experiment 2, the highly experienced sprinters performed the same 10-meter sprint task using the same instructional conditions as in Experiment 1. For the 10-meter sprint time and kinetic variables, there were no significant differences observed across any of the conditions. These results provide new evidence that experience level mediates the influence of attentional focus on sprint performance.

Acute Effects of Loaded Half-Squat Jumps on Sprint Running Speed in Track and Field Athletes and Soccer Players

The purpose of the study was to determine the acute responses to a jump squat protocol designed to induce postactivation potentiation on sprint running performance in experienced track and field athletes and soccer players. Twenty-five regional level athletes (12 track and field: ∼17 years; ∼177 cm; ∼73 kg and 13 soccer: ∼18 years; ∼175 cm; ∼72 kg) performed 2 test sessions assessing 40-m sprint running performance in a balanced, crossover design. Dual-beam light timing gates measured 0-20 and 20-40 m sprint times before and after either 9 minutes of sitting (control) or 2 sets of 6 repetition half-squat jump with the load eliciting maximum power (experimental) conditions. Sprint performance was significantly enhanced over both 0-20 m (3.09 ± 0.07 to 3.04 ± 0.08 seconds; Δ ∼1.5%; p ≤ 0.05) and 20-40 m (2.42 ± 0.09 to 2.39 ± 0.09 seconds; Δ ∼1%; p ≤ 0.05) in track and field athletes only. Also, the magnitude of enhanced sprint performance was related to baseline 0-20 m sprint performance (r = 0.44; p = 0.028; n = 25). It seems that using loaded half-squat jumps to enhance sprint performance could be used in training of high-level young athletes.

Effects of stride frequency and foot position at landing on braking force, hip torque, impact peak force and the metabolic cost of running in humans

Endurance runners are often advised to use 90 strides min(-1), but how optimal is this stride frequency and why? Endurance runners are also often advised to maintain short strides and avoid landing with the feet too far in front of their hips or knees (colloquially termed 'overstriding'), but how do different kinematic strategies for varying stride length at the same stride frequency affect economy and impact peaks? Linear mixed models were used to analyze repeated measures of stride frequency, the anteroposterior position of the foot at landing, V̇O2 , lower extremity kinematics and vertical ground reaction forces in 14 runners who varied substantially in height and body mass and who were asked to run at 75, 80, 85, 90 and 95 strides min(-1) at 3.0 m s(-1). For every increase of 5 strides min(-1), maximum hip flexor moments in the sagittal plane increased by 5.8% (P<0.0001), and the position of the foot at landing relative to the hip decreased by 5.9% (P=0.003). Higher magnitudes of posteriorly directed braking forces were associated with increases in foot landing position relative to the hip (P=0.0005) but not the knee (P=0.54); increases in foot landing position relative to the knee were associated with higher magnitudes (P<0.0001) and rates of loading (P=0.07) of the vertical ground reaction force impact peak. Finally, the mean metabolically optimal stride frequency was 84.8±3.6 strides min(-1), with 50.4% of the variance explained by the trade-off between minimizing braking forces versus maximum hip flexor moments during swing. The results suggest that runners may benefit from a stride frequency of approximately 85 strides min(-1) and by landing at the end of swing phase with a relatively vertical tibia.

Accuracy of PARTwear Inertial Sensor and Optojump Optical Measurement System for Measuring Ground Contact Time During Running

Ammann, R, Taube, W, and Wyss, T. Accuracy of PARTwear inertial sensor and Optojump optical measurement system for measuring ground contact time during running. J Strength Cond Res 30(7): 2057-2063, 2016-The aim of this study was to validate the detection of ground contact time (GCT) during running in 2 differently working systems: a small inertial measurement sensor, PARTwear (PW), worn on the shoe laces, and the optical measurement system, Optojump (OJ), placed on the track. Twelve well-trained subjects performed 12 runs each on an indoor track at speeds ranging from 3.0 to 9.0 m·s. GCT of one step per run (total 144) was simultaneously obtained by the PW, the OJ, and a high-speed video camera (HSC), whereby the latter served as reference system. The sampling rate was 1,000 Hz for all methods. Compared with the HSC, the PW and the OJ systems underestimated GCT by -1.3 ± 6.1% and -16.5 ± 6.7% (p-values ≤ 0.05), respectively. The intraclass correlation coefficients between PW and HSC and between OJ and HSC were 0.984 and 0.853 (p-values < 0.001), respectively. Despite the constant systematic underestimation of GCT, analyses indicated that PW successfully recorded GCT over a wide range of speeds. However, results showed only moderate validity for the OJ system, with increasing errors when speed decreased. In conclusion, the PW proved to be a highly useful and valid application, and its use can be recommended not only for laboratory settings but also for field applications. In contrast, data on GCT obtained by OJ during running must be treated with caution, specifically when running speed changes or when comparisons are made with GCT data collected by other measurement systems.

Relationships and Predictive Capabilities of Jump Assessments to Soccer-Specific Field Test Performance in Division I Collegiate Players

Leg power is an important characteristic for soccer, and jump tests can measure this capacity. Limited research has analyzed relationships between jumping and soccer-specific field test performance in collegiate male players. Nineteen Division I players completed tests of: leg power (vertical jump (VJ), standing broad jump (SBJ), left- and right-leg triple hop (TH)); linear (30 m sprint; 0–5 m, 5–10 m, 0–10, 0–30 m intervals) and change-of-direction (505) speed; soccer-specific fitness (Yo-Yo Intermittent Recovery Test Level 2); and 7 × 30-m sprints to measure repeated-sprint ability (RSA; total time (TT), performance decrement (PD)). Pearson’s correlations (r) determined jump and field test relationships; stepwise regression ascertained jump predictors of the tests (p < 0.05). All jumps correlated with the 0–5, 0–10, and 0–30 m sprint intervals (r = −0.65–−0.90). VJ, SBJ, and left- and right-leg TH correlated with RSA TT (r = −0.51–−0.59). Right-leg TH predicted the 0–5 and 0–10 m intervals (R² = 0.55–0.81); the VJ predicted the 0–30 m interval and RSA TT (R² = 0.41–0.84). Between-leg TH asymmetry correlated with and predicted left-leg 505 and RSA PD (r = −0.68–0.62; R² = 0.39–0.46). Improvements in jumping ability could contribute to faster speed and RSA performance in collegiate soccer players.

Impact of Harness Attachment Point on Kinetics and Kinematics During Sled Towing

Resisted sprint training is performed in a horizontal direction and involves similar muscles, velocities, and ranges of motion (ROM) to those of normal sprinting. Generally, sleds are attached to the athletes through a lead (3 m) and harness; the most common attachment points are the shoulder or waist. At present, it is not known how the different harness point's impact on the kinematics and kinetics associated with sled towing (ST). The aim of the current investigation was to examine the kinetics and kinematics of shoulder and waist harness attachment points in relation to the acceleration phase of ST. Fourteen trained men completed normal and ST trials, loaded at 10% reduction of sprint velocity. Sagittal plane kinematics from the trunk, hip, knee, and ankle were measured, together with stance phase kinetics (third footstrike). Kinetic and kinematic parameters were compared between harness attachments using one-way repeated-measures analysis of variance. The results indicated that various kinetic differences were present between the normal and ST conditions. Significantly greater net horizontal mean force, net horizontal impulses, propulsive mean force, and propulsive impulses were measured (p < 0.05). Interestingly, the waist harness also led to greater net horizontal impulse when compared with the shoulder attachment (p < 0.001). In kinematic terms, ST conditions significantly increased peak flexion in hip, knee, and ankle joints compared with the normal trials (p < 0.05). Results highlighted that the shoulder harness had a greater impact on trunk and knee joint kinematics when compared with the waist harness (p < 0.05). In summary, waist harnesses seem to be the most suitable attachment point for the acceleration phase of sprinting. Sled towing with these attachments resulted in fewer kinematic alterations and greater net horizontal impulse when compared with the shoulder harness. Future research is necessary in order to explore the long-term adaptations of these acute changes.

Acute Response of Well-Trained Sprinters to a 100-m Race: Higher Sprinting Velocity Achieved With Increased Step Rate Compared With Speed Training

This study aimed to clarify the contribution of differences in step length and step rate to sprinting velocity in an athletic race compared with speed training. Nineteen well-trained male and female sprinters volunteered to participate in this study. Sprinting motions were recorded for each sprinter during both 100-m races and speed training (60-, 80-, and 100-m dash from a block start) for 14 days before the race. Repeated-measures analysis of covariance was used to compare the step characteristics and sprinting velocity between race and speed training, adjusted for covariates including race-training differences in the coefficients of restitution of the all-weather track, wind speed, air temperature, and sex. The average sprinting velocity to the 50-m mark was significantly greater in the race than in speed training (8.26 ± 0.22 m·s vs. 8.00 ± 0.70 m·s, p < 0.01). Although no significant difference was seen in the average step length to the 50-m mark between the race and speed training (1.81 ± 0.09 m vs. 1.80 ± 0.09 m, p = 0.065), the average step rate was significantly greater in the race than in speed training (4.56 ± 0.17 Hz vs. 4.46 ± 0.13 Hz, p < 0.01). These findings suggest that sprinters achieve higher sprinting velocity and can run with higher exercise intensity and more rapid motion during a race than during speed training, even if speed training was performed at perceived high intensity.

Spatiotemporal Parameters of 100-m Sprint in Different Levels of Sprinters with Unilateral Transtibial Amputation

The aim of this study was to investigate differences of the spatiotemporal parameters in a 100-m sprint among elite, sub-elite, and non-elite sprinters with a unilateral transtibial amputation. Using publicly available Internet broadcasts, we analyzed 125, 19, and 33 records from 30 elite, 12 sub-elite, and 22 non-elite sprinters, respectively. For each sprinter’s run, the average velocity, step frequency, and step length were calculated using the number of steps in conjunction with the official race time. Average velocity was greatest in elite sprinters (8.71±0.32 m/s), followed by the sub-elite (8.09±0.06 m/s) and non-elite groups (7.72±0.27 m/s). Although there was a significant difference in average step frequency between the three groups, the effect size was small and the relative difference among the three groups was 3.1%. Statistical analysis also revealed that the average step length was longest in elite sprinters, followed by the sub-elite and non-elite groups. These results suggest that the differences in sprint performance between the three groups is mainly due to the average step length rather than step frequency.