Specific muscle-tendon architecture in elite Kenyan distance runners

Sprint runners have longer Achilles tendon moment arm than distance runners

The length of the Achilles tendon moment arm may affect muscle shortening velocity, ankle moment, and running economy in running. Regarding the direction of these effects, experimental studies are controversial. These typically use simplified 2-D methods to define the length of the moment arm, and data on high-level athletes are scarce. The purpose of this study was to use a 3-D approach to estimate the length of the Achilles tendon moment arm and examine its association with sprint and endurance running performance in high-level competitive runners. Twenty-nine healthy adult competitive runners were recruited, including fifteen distance runners (IAAF score = 953 ± 116, mean ± standard deviation) and fourteen sprint runners (IAAF score = 993 ± 113). The length of the Achilles tendon moment arm was estimated from T1 weighted MRI scans taken at a 90° ankle angle. The sprint runners had longer Achilles tendon moment arms compared to the distance runners when considering absolute lengths (51.8 ± 2.1 mm vs. 48.7 ± 3.8 mm, p = 0.017, Cohen's d = -0.94), as well as after normalizing to body height (p = 0.004, d = -1.14). However, we did not find any correlation between the absolute or normalized Achilles tendon moment arm length and personal best running performance in either group. However, longer moment arm may be due to the relatively larger plantar flexor muscle size which can probably offset the detrimental effects of a longer moment arm. On the other hand, distance runners may benefit from a relatively shorter moment arm due to lower forces and increased need for fatigue-resistance. We found no evidence that plantar flexor moment arm is detrimental to running performance in either group, therefore, practitioners should not be concerned about the effects of increasing muscle size on the increase in Achilles tendon moment arm.

The race within a race: Together on the marathon starting line but miles apart in the experience

Every four years the world's best athletes come together to compete in the Olympic games, electrifying audiences with incredible feats of speed, strength, endurance and skill as personal best performances and new records are set. However, the exceptional talent that underpin such performances is incomprehensible to most casual observers who often cannot appreciate how unique these athletes are. In this regard, endurance running, specifically the marathon, a 42.195 km foot race, provides one of the few occasions in sport outside of Olympic, world and national competitions, that permits sport scientists and fans alike to directly compare differences in the physiology between recreational and elite competitors. While these individuals may all cover the same distance, on the same course, on the same day - their experience and the physiological and psychological demands placed upon them are vastly different. There is, in effect, a "race within a race". In the current review we highlight the superior physiology of the elite endurance athlete, emphasizing the gap between elite competitors and well-trained, but less genetically endowed athletes. We draw attention to a range of inconsistencies in how current sports science practices are understood, implemented, and communicated in terms of the elite and not-so-elite endurance athlete.

Physiological parameters and training characteristics of endurance runners at Ethiopian Youth Sports Academy (2400 meters above sea level) and Guna Athletics Sport Club (3100 meters above sea level) training camps: a comparative cross-sectional study

BACKGROUND

Endurance performance is impacted by physiological, anthropometrical, diet, genetic, psychological, and training characteristics. Altitude can affect physiological parameters (like maximum oxygen utilization, arterial oxygen saturation (SaO2), heart rate, and blood pressure) and training characteristics (duration, frequency, and training load). Thus, this study compared physiological parameters and training characteristics between endurance runners at Ethiopian Youth Sports Academy (EYSA) and Guna Athletics Sport Club (GASC) located which are located at elevation of 2400 and 3100 meters, respectively.

METHODS

A comparative cross-sectional study design was used from September to November 2021. Data was obtained from a total of 120 eligible participants (30 runners and 30 controls at GASC, and 30 runners and 30 controls at EYSA). Sociodemographic and training characteristics were assessed using self-administered standardized questionnaires. SaO2 and heart rate were measured using finger pulse-oximetry (Nellcor, Oxim N-65; Covidien, Dublin, Ireland). Blood pressure was measured by Folee Digital Blood Pressure Monitor DX-B1 (Jiangsu Folee Medical Equipment Co., Ltd., Zhenjiang, China).

RESULTS

The runners of GASC had significantly lower resting SaO2, SaO2 immediately after maximal exertion, training (frequency and load) than runners of EYSA in both sexes. Runners of Guna Athletics Sport Club (RGASC) had significantly higher maximum oxygen utilization (VO2max) than Runners Ethiopian Youth Sports Academy (REYSA) in both sexes. Severe exercise-induced hypoxemia (EIAH) and moderate EIAH were developed by male runners of GASC and EYSA respectively. Besides, female runners GASC and EYSA developed moderate and mild EIAH, respectively.

CONCLUSIONS

Conclusively, there were significant differences in physiological parameters and training load between RGASC and REYSA. High altitude (3100 meters) may have a greater impact on the above variables than moderate hypoxia (2400 meters above sea level). Hence, endurance runner coaches should give emphasis to these variables.

The fourth dimension: physiological resilience as an independent determinant of endurance exercise performance

Endurance exercise performance is known to be closely associated with the three physiological pillars of maximal O2 uptake (V ̇ O 2 max $\dot{V}_{{\rm O}_{2}{\rm max}}$ ), economy or efficiency during submaximal exercise, and the fractional utilisation ofV ̇ O 2 max $\dot{V}_{{\rm O}_{2}{\rm max}}$ (linked to metabolic/lactate threshold phenomena). However, while 'start line' values of these variables are collectively useful in predicting performance in endurance events such as the marathon, it is not widely appreciated that these variables are not static but are prone to significant deterioration as fatiguing endurance exercise proceeds. For example, the 'critical power' (CP), which is a composite of the highest achievable steady-state oxidative metabolic rate and efficiency (O2 cost per watt), may fall by an average of 10% following 2 h of heavy intensity cycle exercise. Even more striking is that the extent of this deterioration displays appreciable inter-individual variability, with changes in CP ranging from <1% to ∼32%. The mechanistic basis for such differences in fatigue resistance or 'physiological resilience' are not resolved. However, resilience may be important in explaining superlative endurance performance and it has implications for the physiological evaluation of athletes and the design of interventions to enhance performance. This article presents new information concerning the dynamic plasticity of the three 'traditional' physiological variables and argues that physiological resilience should be considered as an additional component, or fourth dimension, in models of endurance exercise performance.

Muscle morphology and architecture of the medial gastrocnemius between typically developing children with different ancestral background

Muscle ultrasonography is frequently used to improve the understanding of musculoskeletal impairments in children with spastic cerebral palsy (SCP). So far, most studies on muscle morphology and architecture have included typically developing children and children with SCP with similar ancestry, being mainly Caucasian. Less is known about differences in muscle morphology between children with different ancestral backgrounds. Therefore, the aim of this study was to compare muscle morphology and architecture of the medial gastrocnemius in typically developing children with African, South Asian and Southeast Asian descent from Suriname. This explorative cohort study identified children as Maroon (Ghana, African descent), Hindustani (India, South Asian) or Javanese (Indonesia, Southeast Asian), aged 5-10 years. Using 3D freehand ultrasound with the subject prone, the following medial gastrocnemius parameters were defined: muscle tendon unit (MTU) length, muscle belly length, tendon length, muscle volume, muscle thickness, anatomical cross-sectional area (ACSA), fascicle length, pennation angle, and physiological cross-sectional area (PCSA). In addition, differences between ancestral groups were assessed for the length of the MTU, muscle, tendon and fascicles in two passive stretch conditions corresponding to an externally applied joint torque of 1Nm and 4Nm. One-way ANOVA with post hoc t-tests were used to investigate differences between the ancestral groups. In total, 100 Hindustani (n = 34), Javanese (n = 34) and Maroon (n = 32) children were included. For statistical analyses, we matched the children by age, which resulted in groups of 25 children per ancestral group (n = 75). There were no differences found in MTU length, muscle belly length, ACSA, PCSA and muscle volume. Tendon length, fascicle length and pennation angle were different between ancestral groups. Compared to Javanese children, tendon length was longer (p = 0.001) and pennation angle (p = 0.001) was larger in Maroon children and fascicle length was shorter in both Maroon and Hindustani children (p < 0.001). While there was a difference found in MTU length at different conditions of passive stretch between ancestries, no differences were found in the muscle, tendon and fascicles. This is the first study that investigated macroscopic morphological and architectural parameters for the medial gastrocnemius in one extended cohort of typically developing children, stratified in three ancestral subgroups. The current results imply that ancestry-specific reference data for children are needed, especially for tendon length, fascicle length and pennation angle when investigating altered muscle morphology in neurological or neuromuscular pathologies, such as SCP. Future studies should report the ancestral background when describing muscle morphology and architecture of children and ancestral specifications should be included in normative databases.

A longer Achilles tendon moment arm length is not associated with superior hopping performance

Variability in musculoskeletal and lower leg structure has the potential to influence hopping height. Achilles tendon moment arm length and plantarflexor muscle strength can influence ankle joint torque development and, consequently, hopping performance. While most studies have examined the connection of the Achilles tendon moment arm with hopping performance including the resting length, in this study we attempted to explore how the changes in Achilles tendon moment arm are related to hopping performance. Therefore, the purpose of this study was to test for correlations between foot and lower leg muscle structure parameters (i.e., muscle mass, volume, cross-sectional area and Achilles tendon moment arm length) and hopping height performance in relation to changes in Achilles tendon moment arm length. Eighteen participants (10 males 8 female) performed repetitive bilateral hopping on a force platform while sagittal plane kinematics of the lower leg were recorded. Additionally, maximal isometric plantarflexion was measured. To obtain structural parameters of the lower leg, the right lower leg of each participant was scanned with magnetic resonance imaging. The cross-sectional areas of the Achilles tendon, soleus, lateral and medial gastrocnemius were measured, while muscle volumes, muscle mass, and Achilles tendon moment arm length were calculated. Contrary to our initial assumption, longer Achilles tendon moment arm did not result in superior hopping performance. Interestingly, neither maximal isometric plantarflexion force nor muscle size correlated with repetitive bilateral hopping performance. We can assume that the mechanical characteristics of the tendon and the effective utilization of the stored strain energy in the tendon may play a more important role in repetitive hopping than the structural parameters of the lower leg.

Architectural anatomy of the human tibialis anterior presents morphological asymmetries between superficial and deep unipennate regions

The tibialis anterior muscle plays a critical role in human ambulation and contributes to maintaining the upright posture. However, little is known about its muscle architecture in males and females. One hundred and nine physically active males and females were recruited. Tibialis anterior muscle thickness, pennation angle, and fascicle length were measured at rest in both unipennate regions of both legs using real-time ultrasound imaging. A linear mixed model was used with muscle thickness, pennation angle, or fascicle length as the dependent variables. All models were carried out with and without total leg lean mass and shank length as covariates. Causal mediation analysis was computed to explore the effect of muscle thickness on the relationship between fascicle length and pennation angle. There were no significant differences between dominant and nondominant legs regarding muscle architecture. Muscle thickness and pennation angle were greater in the deep than the superficial unipennate region in males (1.9 mm and 1.1°, p < 0.001) and women (3.4 mm and 2.2°, p < 0.001). However, the fascicle length was similar in both regions for both sexes. The differences remained significant after accounting for differences in leg lean mass and shank length. In both regions, muscle thickness was 1-3 mm greater in males and superficial pennation angle 2° smaller in females (both, p < 0.001). After accounting for leg lean mass and shank length, sex differences remained for muscle thickness (1.6 mm, p < 0.05) and pennation angle (3.4°, p < 0.001) but only in the superficial region. In both regions, leg lean mass and shank-adjusted fascicle length were 1.4 mm longer in females than males (p < 0.05). The causal mediation analysis revealed that the estimation of fascicle length was positive, suggesting that a 10% increase in muscle thickness would augment the fascicle length, allowing a 0.38° pennation angle decrease. Moreover, the pennation angle increases in total by 0.54° due to the suppressive effect of the increase in fascicle length. The estimated mediation, direct, and total effects were all significantly different from zero (p < 0.001). Overall, our results indicate that the architectural anatomy of the tibialis anterior shows sexual dimorphism in humans. Tibialis anterior presents morphological asymmetries between superficial and deep unipennate regions in both sexes. Lastly, our causal mediation model identified a suppressive effect of fascicle length on the pennation angle, suggesting that increments in muscle thickness are not always aligned with increments in fascicle length or the pennation angle.

Assessing spring-mass similarity in elite and recreational runners

The dynamic complexity and individualization of running biomechanics has challenged the development of objective and comparative gait measures. Here, we present and explore several novel biomechanical metrics for running that are informed by a canonical inter-species gait template-the spring-mass model. The measures assess running mechanics systemically against the template via quantifying characteristics of a runner's kinetics relative to the energy-conserving elastic system-i.e., their "spring-mass similarity". Applying these metrics in a retrospective cohort investigation, we studied the overground kinetics of two heterogenous populations of runners in two footwear conditions: elite and recreational athletes in shod and barefoot conditions. Across all measures and within foot strike types, the elite runners exhibited mechanics that were more similar to those of the ideally elastic spring-mass template. The elite runners had more symmetric bounces, less discrepancy (i.e., greater coordination) between horizontal and vertical kinetic changes, and better fit to a spring-mass vertical ground reaction force time series. Barefoot running elicited greater kinetic coordination in the recreational runners. At a faster speed, the elites further improved their similarity to the template. Overall, the more economical elite group exhibited greater likeness to the linearly elastic, energy-conserving spring-mass system than their recreational counterparts. This study introduces novel biomechanical measures related to performance in distance running. More broadly, it provides new, approachable metrics for systemic quantification of gait biomechanics in runners across all demographics. These metrics may be applied to assess a runner's global biomechanical response to a variety of interventions, including training adaptations, rehabilitation programs, and footwear conditions.

Achilles tendon dimensions, ankle stiffness and footfall patterns in recreational runners

The main purpose of this study was to investigate the relationship among Achilles tendon (AT) dimensions, ankle joint stiffness, and footfall patterns in recreational rearfoot and non-rearfoot runners. Based on the foot strike index, a total of 107 runners were divided into rearfoot (47 females/40 males) and non-rearfoot runners (14 females/6 males). All participants had theirs AT dimensions (AT length, AT thickness, and AT moment arm) measured using a combination of ultrasound and motion capture systems. In addition, all performed running trials measured at self-selected speed in laboratory-neutral shoes. A partial correlation coefficient was used for correlations between the selected variables. The results revealed a significant relationship between ankle joint stiffness and level of footfall pattern in rearfoot (r = 0.232, p = 0.032) and non-rearfoot runners (r = -0.811, p < 0.001). The results also suggest a relationship between AT thickness and foot strike index (r = -0.486) in non-rearfoot runners. Runners whose footfall pattern is closer to the heel have greater ankle joint stiffness. Non-rearfoot runners whose footfall pattern is closer to the toe have a thinner AT. Non-rearfoot runners with thicker AT had greater ankle joint stiffness.

Is the muscle-tendon architecture of non-athletic Kenyans different from that of Japanese and French males?

BACKGROUND

In endurance running, elite Kenyan runners are characterized by longer thigh, shank, and Achilles tendon (AT) lengths combined with shorter fascicles and larger medial gastrocnemius (MG) pennation angles than elite Japanese runners. These muscle-tendon characteristics may contribute to the running performance of Kenyans. Furthermore, these specific lower-leg musculoskeletal architectures have been confirmed not only in elite Kenyan runners but also in non-athletic Kenyans since early childhood. However, it remains questionable whether the differences in muscle-tendon architecture between Kenyans and Japanese differ from those of European Caucasians. Therefore, this study aimed to compare anthropometry and muscle-tendon architecture of young non-athletic Kenyan males with their Japanese and French counterparts.

METHODS

A total of 235 young non-athletic males, aged 17-22 years, volunteered. The anthropometric measures, thigh, and shank lengths, as well as AT and MG muscle architecture, were measured using ultrasonography and a tape measure. Inter-group differences in anthropometry and muscle-tendon architecture were tested using one-way ANOVA and ANCOVA analyses controlling for shank length and muscle thickness.

RESULTS

The anthropometric and muscle-tendon characteristics of the non-athletic French were closer to those of the Kenyans than to those of the Japanese. However, the ultrasonography analysis confirmed that the non-athletic Kenyans had the longest AT as well as the shortest MG fascicles and the largest pennation angle compared to the French and Japanese, even after controlling for shank length and muscle thickness with ANCOVA, respectively.

CONCLUSIONS

These results confirmed the specificity of the muscle-tendon architecture of the triceps surae in Kenyans in comparison to their Japanese and French counterparts in non-athletic adults. This study provides additional support to the fact that Kenyans may have musculotendinous advantages in endurance running.

Progressive daily hopping exercise improves running economy in amateur runners: a randomized and controlled trial

This study investigated the effects of a daily plyometric hopping intervention on running economy (RE) in amateur runners. In a randomized, controlled trial, thirty-four amateur runners (29 ± 7 years, 27 males) were allocated to a control or a hopping exercise group. During the six-week study, the exercise group performed 5 min of double-legged hopping exercise daily. To progressively increase loading, the number of hopping bouts (10 s each) was steadily increased while break duration between sets was decreased. Pre- and post-intervention, RE, peak oxygen uptake (VO_2peak), and respiratory exchange ratio (RER) were measured during 4-min stages at three running speeds (10, 12, and 14 km/h). ANCOVAs with baseline values and potential cofounders as cofactors were performed to identify differences between groups. ANCOVA revealed an effect of hopping on RE at 12 km/h (df = 1; F = 4.35; p < 0.05; η² = 0.072) and 14 km/h (df = 1; F = 6.72; p < 0.05; η² = 0.098), but not at 10 km/h (p > 0.05). Exercise did not affect VO_2peak (p > 0.05), but increased RER at 12 km/h (df = 1; F = 4.26; p < 0.05; η² = 0.059) and 14 km/h (df = 1; F = 36.73; p < 0.001; η² = 0.520). No difference in RER was observed at 10 km/h (p > 0.05). Daily hopping exercise is effective in improving RE at high running speeds in amateurs and thus can be considered a feasible complementary training program.Clinical trial registration German Register of Clinical Trials (DRKS00017373).

Variability in Running Economy of Kenyan World-Class and European Amateur Male Runners with Advanced Footwear Running Technology: Experimental and Meta-analysis Results

BACKGROUND

Advanced footwear technology improves average running economy compared with racing flats in sub-elite athletes. However, not all athletes benefit as performance changes vary from a 10% drawback to a 14% improvement. The main beneficiaries from such technologies, world-class athletes, have only been analyzed using race times.

OBJECTIVE

The aim of this study was to measure running economy on a laboratory treadmill in advanced footwear technology compared to a traditional racing flat in world-class Kenyan (mean half-marathon time: 59:30 min:s) versus European amateur runners.

METHODS

Seven world-class Kenyan and seven amateur European male runners completed a maximal oxygen uptake assessment and submaximal steady-state running economy trials in three different models of advanced footwear technology and a racing flat. To confirm our results and better understand the overall effect of new technology in running shoes, we conducted a systematic search and meta-analysis.

RESULTS

Laboratory results revealed large variability in both world-class Kenyan road runners, which ranged from a 11.3% drawback to a 11.4% benefit, and amateur Europeans, which ranged from a 9.7% benefit to a 1.1% drawback in running economy of advanced footwear technology compared to a flat. The post-hoc meta-analysis revealed an overall significant medium benefit of advanced footwear technology on running economy compared with traditional flats.

CONCLUSIONS

Variability of advanced footwear technology performance appears in both world-class and amateur runners, suggesting further testing should examine such variability to ensure validity of results and explain the cause as a more personalized approach to shoe selection might be necessary for optimal benefit.

How do differences in Achilles' tendon moment arm lengths affect muscle-tendon dynamics and energy cost during running?

Introduction

The relationship between the Achilles tendon moment arm length (AT_MA) and the energy cost of running (E_run) has been disputed. Some studies suggest a short AT_MA reduces E_run while others claim a long AT_MA reduces E_run. For a given ankle joint moment, a short AT_MA permits a higher tendon strain energy storage, whereas a long AT_MA reduces muscle fascicle force and muscle energy cost but shortening velocity is increased, elevating the metabolic cost. These are all conflicting mechanisms to reduce E_run, since AT energy storage comes at a metabolic cost. Neither of these proposed mechanisms have been examined together.

Methods

We measured AT_MA using the tendon travel method in 17 males and 3 females (24 ± 3 years, 75 ± 11 kg, 177 ± 7 cm). They ran on a motorized treadmill for 10 min at 2.5 m · s^-1 while E_run was measured. AT strain energy storage, muscle lengths, velocities and muscle energy cost were calculated during time-normalized stance from force and ultrasound data. A short (SHORT n = 11, AT_MA = 29.5 ± 2.0 mm) and long (LONG, n = 9, AT_MA = 36.6 ± 2.5 mm) AT_MA group was considered based on a bimodal distribution of measured AT_MA.

Results

Mean E_run was 4.9 ± 0.4 J · kg^-1 · m^-1. The relationship between AT_MA and E_run was not significant (r ² = 0.13, p = 0.12). Maximum AT force during stance was significantly lower in LONG (5,819 ± 1,202 N) compared to SHORT (6,990 ± 920 N, p = 0.028). Neither AT stretch nor AT strain energy storage was different between groups (mean difference: 0.3 ± 1 J · step^-1, p = 0.84). Fascicle force was significantly higher in SHORT (508 ± 93 N) compared to LONG (468 ± 84 N. p = 0.02). Fascicle lengths and velocities were similar between groups (p > 0.72). Muscle energy cost was significantly lower in LONG (0.028 ± 0.08 J · kg · step^-1) compared to SHORT (0.045 ± 0.14 J · kg · step^-1 p = 0.004). There was a significant negative relationship between AT_MA and total muscle energy cost relative to body mass across the stance phase (r = -0.699, p < 0.001).

Discussion

Together these results suggest that a LONG AT_MA serves to potentially reduce E_run by reducing the muscle energy cost of the plantarflexors during stance. The relative importance of AT energy storage and return in reducing E_run should be re-considered.

Does the Achilles Tendon Influence Foot Strike Patterns During an Exhaustive Run?

The study purpose was to investigate whether there is a relationship between the Achilles tendon (AT) length, moment arm length, and the foot strike pattern (FP) change during an exhaustive run (EXR) in nonrearfoot FP runners. Twenty-eight runners were recruited and divided into 2 groups (highly trained/moderately trained) according to their weekly training volume. Participants underwent the graded exercise test, the EXR with biomechanical analysis at the beginning, and at the end, and the magnetic resonance imaging scan of the AT. Correlations were used to assess associations between FP change (value of the difference between end and beginning) and the selected performance and AT variables. AT length significantly correlated with the FP change according to foot strike angle (r = -.265, P = .049). The AT moment arm length significantly correlated with the FP change according to strike index during EXR (r = -.536, P = .003). Multiple regression showed that AT length was a significant predictor for the FP change according to foot strike angle if the second predictor was the graded exercise test duration and the third predictor was training group association. These results suggest that a runner's training volume, along with a longer AT and AT moment arm appear to be associated with the ability to maintain a consistent FP during EXR by nonrearfoot FP runners.

Muscle-tendon architecture in Kenyans and Japanese: Potential role of genetic endowment in the success of elite Kenyan endurance runners

AIM

The specificity of muscle-tendon and foot architecture of elite Kenyan middle- and long-distance runners has been found to contribute to their superior running performance. To investigate the respective influence of genetic endowment and training on these characteristics, we compared leg and foot segmental lengths as well as muscle-tendon architecture of Kenyans and Japanese males (i) from infancy to adulthood and (ii) non-athletes versus elite runners.

METHODS

The 676 participants were divided according to their nationality (Kenyans and Japanese), age (nine different age groups for non-athletes) and performance level in middle- and long-distance races (non-athlete, non-elite and elite adult runners). Shank and Achilles tendon (AT) lengths, medial gastrocnemius (MG) fascicle length, pennation angle and muscle thickness, AT moment arm (MA_AT ), and foot lever ratio were measured.

RESULTS

Above 8 years old, Kenyans had a longer shank and AT, shorter fascicle, greater pennation angle, thinner MG muscle as well as longer MA_AT , with lower foot lever ratio than age-matched Japanese. Among adults of different performance levels and independently of the performance level, Kenyans had longer shank, AT and MA_AT , thinner MG muscle thickness, and lower foot lever ratio than Japanese. The decrease in MG fascicle length and increase pennation angle observed for the adult Japanese with the increase in performance level resulted in a lack of difference between elite Kenyans and Japanese.

CONCLUSION

The specificity of muscle-tendon and foot architecture of elite Kenyan runners could result from genetic endowment and contribute to the dominance of Kenyans in middle- and long-distance races.

Non-South East Asians have a better running economy and different anthropometrics and biomechanics than South East Asians

Running biomechanics and ethnicity can influence running economy (RE), which is a critical factor of running performance. Our aim was to compare RE of South East Asian (SEA) and non-South East Asian (non-SEA) runners at several endurance running speeds (10-14 km/h) matched for on-road racing performance and sex. Secondly, we explored anthropometric characteristics and relationships between RE and anthropometric and biomechanical variables. SEA were 6% less economical (p = 0.04) than non-SEA. SEA were lighter and shorter than non-SEA, and had lower body mass indexes and leg lengths (p ≤ 0.01). In terms of biomechanics, a higher prevalence of forefoot strikers in SEA than non-SEA was seen at each speed tested (p ≤ 0.04). Furthermore, SEA had a significantly higher step frequency (p = 0.02), shorter contact time (p = 0.04), smaller footstrike angle (p < 0.001), and less knee extension at toe-off (p = 0.03) than non-SEA. Amongst these variables, only mass was positively correlated to RE for both SEA (12 km/h) and non-SEA (all speeds); step frequency, negatively correlated to RE for both SEA (10 km/h) and non-SEA (12 km/h); and contact time, positively correlated to RE for SEA (12 km/h). Despite the observed anthropometric and biomechanical differences between cohorts, these data were limited in underpinning the observed RE differences at a group level. This exploratory study provides preliminary indications of potential differences between SEA and non-SEA runners warranting further consideration. Altogether, these findings suggest caution when generalizing from non-SEA running studies to SEA runners.

Factors correlated with running economy among elite middle- and long-distance runners

Running economy (RE) at a given submaximal running velocity is defined as oxygen consumption per minute per kg body mass. We investigated RE in a group of 12 male elite runners of national class. In addition to RE at 14 and 18 km h-1 we measured the maximal oxygen consumption (VO2max ) and anthropometric measures including the moment arm of the Achilles tendon (LAch ), shank and foot volumes, and muscular fascicle lengths. A 3-D biomechanical movement analysis of treadmill running was also conducted. RE was on average 47.8 and 62.3 ml O2  min-1  kg-1 at 14 and 18 km h-1 . Maximal difference between the individual athletes was 21% at 18 km h-1 . Mechanical work rate was significantly correlated with VO2 measured in L min-1 at both running velocities. However, RE and relative work rate were not significantly correlated. LAch was significantly correlated with RE at 18 km h-1 implying that a short moment arm is advantageous regarding RE. Neither foot volume nor shank volume were significantly correlated to RE. Relative muscle fascicle length of m. soleus was significantly correlated with RE at 18 km h-1 . Whole body stiffness and leg stiffness were significantly correlated with LAch indicating that a short moment arm coincided with high stiffness. It is concluded that a short LAch is correlated with RE. Probably, a short LAch allows for storage of a larger amount of elastic energy in the tendon and influences the force-velocity relation toward a lower contraction velocity.

Relationship between Step Characteristics and Race Performance during 5000-m Race

This study examined the relationship between step characteristics and race time in a 5000-m race. Twenty-one male Japanese endurance runners performed a 5000-m race. Step length, step frequency, contact time, and flight time of two gait cycles (i.e., four consecutive ground contacts) were measured every 400-m by using high-speed video image. Moreover, step length was normalized to body height to minimize the effect of body size. In addition to step characteristics on each lap, the averages of all laps and the per cent change from the first half to the second half were calculated. The average step frequency and step length normalized to body height correlated significantly with the 5000-m race time (r = −0.611, r = −0.575, respectively, p < 0.05 for both). Per cent changes in contact time and step length correlated significantly with the 5000-m race time (r = 0.514, r = −0.486, respectively, p < 0.05 for both). These findings suggest that, in addition to higher step frequency and step length normalized to body height, smaller changes in step length during a given race may be an important step characteristic to achieving superior race performance in endurance runners.

Shorter Ground Contact Time and Better Running Economy: Evidence From Female Kenyan Runners

ABSTRACT

Mooses, M, Haile, DW, Ojiambo, R, Sang, M, Mooses, K, Lane, AR, and Hackney, AC. Shorter ground contact time and better running economy: evidence from female Kenyan runners. J Strength Cond Res 35(2): 481-486, 2021-Previously, it has been concluded that the improvement in running economy (RE) might be considered as a key to the continued improvement in performance when no further increase in V̇o2max is observed. To date, RE has been extensively studied among male East African distance runners. By contrast, there is a paucity of data on the RE of female East African runners. A total of 10 female Kenyan runners performed 3 × 1,600-m steady-state run trials on a flat outdoor clay track (400-m lap) at the intensities that corresponded to their everyday training intensities for easy, moderate, and fast running. Running economy together with gait characteristics was determined. Subjects showed moderate to very good RE at the first (202 ± 26 ml·kg-1·km-1) and second (188 ± 12 ml·kg-1·km-1) run trials, respectively. Correlation analysis revealed significant relationship between ground contact time (GCT) and RE at the second run (r = 0.782; p = 0.022), which represented the intensity of anaerobic threshold. This study is the first to report the RE and gait characteristics of East African female athletes measured under everyday training settings. We provided the evidence that GCT is associated with the superior RE of the female Kenyan runners.

How do training experience and geographical origin of a runner affect running biomechanics?

BACKGROUND

Several studies compared African runners with runners from other places with difference ethnicities to identify biomechanical factors that may contribute to their extraordinary running performance. However, most studies only assessed runners at the elite level. Whether the performance difference was a result of nature or nurture remains unclear.

RESEARCH QUESTIONS

This case study aimed to assess the effect of geographical origin and the effect of training on running biomechanics.

METHODS

We recruited twenty male runners from two regions (Asian and Africa) at two performance levels (elite and recreational), and asked them to run on an instrumented treadmill at 12 km∙h^-1. We measured running kinetics and kinematics parameters, and focused on the parameters that have been shown associated with running performance. We used Friedman test to compare the effect of geographical origin and training on running biomechanics.

RESULTS

Compared to recreational runners, elite runners applied higher amount of ground reaction force in both vertical and anterior-posterior directions (P <  0.05, Cohen's d = 1.63-2.03), together with a longer aerial time (P =  0.039, Cohen's d = 1.11). On the other hand, African runners expressed higher vertical stiffness than Asian runners (P =  0.027, Cohen's d = 0.98). However, the increased vertical stiffness in African runners did not lead to a higher vertical loading rate (P >  0.555, Cohen's d < 0.3), which could be a result of a lower footstrike angle during landing (P =  0.012, Cohen's d = 1.36).

SIGNIFICANCE

For elite runners, the higher amount of ground reaction force might facilitate a longer aerial time, but could also lead to higher amount of mechanical energy loss. African runners expressed higher vertical stiffness and higher step rate, which might lead to a lower CoM vertical displacement, and furthermore reduce mechanical energy loss.

Longer Achilles tendon moment arm results in better running economy

Based on the current literature, the link between Achilles tendon moment arm length and running economy is not well understood. Therefore, the aim of this study was to further investigate the connection between Achilles tendon moment arm and running economy and the influence of Achilles tendon moment arm on the function of the plantarflexor muscle-tendon unit during running.Ten male competitive marathon runners volunteered for this study. The participants ran on a treadmill at two running speeds: 3 and 3.5 m s-1. During running the oxygen consumption, lower leg kinematics, electrical activity of plantar flexor muscles, and fascicle behavior of the lateral gastrocnemius were measured simultaneously. On the second occasion, an MRI scan of the right leg was taken and used to estimate the Achilles tendon moment arm length.There was a negative correlation between running economy and the body height normalized moment arm length at both selected speeds (r = -0.68, P = 0.014 and r = -0.70, P = 0.01). In addition, Achilles tendon moment arm length correlated with the amplitude of the ankle flexion at both speeds (r = -0.59, P = 0.03 and r = -0.60, P = 0.03) and with the electrical activity of the medial gastrocnemius muscle at 3 m s-1 speed (r = -0.62, P = 0.02). Our finding supports the concept that a longer moment arm could be beneficial for distance runners.

Achilles Tendon Length Is Not Related to 100-m Sprint Time in Sprinters

This study examined the relationship between Achilles tendon (AT) length and 100-m sprint time in sprinters. The AT lengths at 3 different portions of the triceps surae muscle in 48 well-trained sprinters were measured using magnetic resonance imaging. The 3 AT lengths were calculated as the distance from the calcaneal tuberosity to the muscle-tendon junction of the soleus, gastrocnemius medialis, and gastrocnemius lateralis, respectively. The absolute 3 AT lengths did not correlate significantly with personal best 100-m sprint time (r = -.023 to .064, all Ps > .05). Furthermore, to minimize the differences in the leg length among participants, the 3 AT lengths were normalized to the shank length, and the relative 3 AT lengths did not correlate significantly with personal best 100-m sprint time (r = .023 to .102, all Ps > .05). Additionally, no significant correlations were observed between the absolute and relative (normalized to body mass) cross-sectional areas of the AT and personal best 100-m sprint time (r = .012 and .084, respectively, both Ps > .05). These findings suggest that the AT morphological variables, including the length, may not be related to superior 100-m sprint time in sprinters.

Lower leg muscle-tendon unit characteristics are related to marathon running performance

The human ankle joint and plantar flexor muscle–tendon unit play an important role in endurance running. It has been assumed that muscle and tendon interactions and their biomechanical behaviours depend on their morphological and architectural characteristics. We aimed to study how plantar flexor muscle characteristics influence marathon running performance and to determine whether there is any difference in the role of the soleus and gastrocnemii. The right lower leg of ten male distance runners was scanned with magnetic resonance imagining. The cross-sectional areas of the Achilles tendon, soleus, and lateral and medial gastrocnemius were measured, and the muscle volumes were calculated. Additional ultrasound scanning was used to estimate the fascicle length of each muscle to calculate the physiological cross-sectional area. Correlations were found between marathon running performance and soleus volume (r = 0.55, p = 0.048), soleus cross-sectional area (r = 0.57, p = 0.04), soleus physiological cross-sectional area (PCSA-IAAF r = 0.77, p < 0.01, CI± 0.28 to 0.94), Achilles tendon thickness (r = 0.65, p < 0.01), and soleus muscle-to-tendon ratio (r = 0.68, p = 0.03). None of the gastrocnemius characteristics were associated with marathon performance. We concluded that a larger soleus muscle with a thicker Achilles tendon is associated with better marathon performance. Based on these results, it can be concluded the morphological characteristics of the lower leg muscle–tendon unit correlate with running performance.

Effects of Achilles Tendon Moment Arm Length on Insertional Achilles Tendinopathy

Insertional Achilles tendinopathy (IAT) is caused by traction force of the tendon. The effectiveness of the suture bridge technique in correcting it is unknown. We examined the moment arm in patients with IAT before and after surgery using the suture bridge technique, in comparison to that of healthy individuals. We hypothesized that the suture bridge method influences the moment arm length. An IAT group comprising 10 feet belonging to 8 patients requiring surgical treatment for IAT were followed up postoperatively and compared with a control group comprising 15 feet of 15 healthy individuals with no ankle complaints or history of trauma or surgery. The ratio of the moment arm (MA) length/foot length was found to be statistically significant between the control group, the IAT group preoperatively and the IAT group postoperatively (p < 0.01). Despite no significant difference in the force between the control and preoperative IAT groups, a significantly higher force to the Achilles tendon was observed in the IAT group postoperatively compared to the other groups (p < 0.05). This study demonstrates that a long moment arm may be one of the causes of IAT, and the suture bridge technique may reduce the Achilles tendon moment arm.

Calcaneus height is a key morphological factor of sprint performance in sprinters

This study examined the relationships between the foot bone morphologies and sprint performance in sprinters. Foot images in 56 male sprinters obtained using magnetic resonance imaging. The relative lengths of the forefoot bones of the big and second toes, which were calculated as total lengths of the forefoot bones for each toe normalized to the foot length, correlated significantly with personal best 100-m sprint time (r =  − 0.293 and − 0.459, both Ps < 0.05). The relative lengths of the rearfoot talus and calcaneus normalized to the foot length also correlated significantly with the sprint performance (r =  − 0.378 and − 0.496, both Ps < 0.05). Furthermore, the relative height of the calcaneus, but not the talus, normalized to body height correlated significantly with sprint performance (r =  − 0.690, P < 0.001). Additionally, the relative calcaneus height correlated significantly with the foot arch height index (r = 0.420, P = 0.001), and the foot arch height index correlated significantly with sprint performance (r =  − 0.517, P < 0.001). These findings suggest that the taller calcaneus may be a key morphological factor for achieving superior sprint performance, potentially via modeling the longer forefoot and rearfoot bones and functional foot morphology in sprinters.

A Pilot Study of Musculoskeletal Abnormalities in Patients in Recovery from a Unilateral Rupture-Repaired Achilles Tendon

The purpose of this study was to compare the inter-limb joint kinematics, joint moments, muscle forces, and joint reaction forces in patients after an Achilles tendon rupture (ATR) via subject-specific musculoskeletal modeling. Six patients recovering from a surgically repaired unilateral ATR were included in this study. The bilateral Achilles tendon (AT) lengths were evaluated using ultrasound imaging. The three-dimensional marker trajectories, ground reaction forces, and surface electromyography (sEMG) were collected on both sides during self-selected speed during walking, jogging and running. Subject-specific musculoskeletal models were developed to compute joint kinematics, joint moments, muscle forces and joint reaction forces. AT lengths were significantly longer in the involved side. The side-to-side triceps surae muscle strength deficits were combined with decreased plantarflexion angles and moments in the injured leg during walking, jogging and running. However, the increased knee extensor femur muscle forces were associated with greater knee extension degrees and moments in the involved limb during all tasks. Greater knee joint moments and joint reaction forces versus decreased ankle joint moments and joint reaction forces in the involved side indicate elevated knee joint loads compared with reduced ankle joint loads that are present during normal activities after an ATR. In the frontal plane, increased subtalar eversion angles and eversion moments in the involved side were demonstrated only during jogging and running, which were regarded as an indicator for greater medial knee joint loading. It seems after an ATR, the elongated AT accompanied by decreased plantarflexion degrees and calf muscle strength deficits indicates ankle joint function impairment in the injured leg. In addition, increased knee extensor muscle strength and knee joint loads may be a possible compensatory mechanism for decreased ankle function. These data suggest patients after an ATR may suffer from increased knee overuse injury risk.

The Potential Relationship Between Leg Bone Length and Running Performance in Well-Trained Endurance Runners

The present study aimed to determine the relationship between leg bone length and running performance in well-trained endurance runners. The lengths of the leg bones in 42 male endurance runners (age: 20.0 ± 1.0 years, body height: 169.6 ± 5.6 cm, body mass: 56.4 ± 5.1 kg, personal best 5000-m race time: 14 min 59 s ± 28 s) were measured using magnetic resonance imaging. The lengths of the femur and tibia were calculated to assess the upper and lower leg lengths, respectively. The total length of the femur + tibia was calculated to assess the overall leg bone length. These lengths of the leg bones were normalized with body height, which was measured using a stadiometer to minimize differences in body size among participants. The relative tibial length was significantly correlated with personal best 5000-m race time (r = -0.328, p = 0.034). Moreover, a trend towards significance was observed in the relative femoral length (r = -0.301, p = 0.053). Furthermore, the relative total lengths of the femur + tibia were significantly correlated with personal best 5000-m race time (r = -0.353, p < 0.05). These findings suggest that although the relationship between the leg bone length and personal best 5000-m race time was relatively minor, the leg bone length, especially of the tibia, may be a potential morphological factor for achieving superior running performance in well-trained endurance runners.

A Comparison of Bilateral and Unilateral Drop Jumping Tasks in the Assessment of Vertical Stiffness

This study sought to compare vertical stiffness during bilateral and unilateral drop jumping. Specifically, the intersession reliabilities and force-deformation profiles associated with each task were to be examined. On 3 occasions, following familiarization, 14 healthy males (age: 22 [2] y; height: 1.77 [0.08] m; and body mass: 73.5 [8.0] kg) performed 3 bilateral, left leg and right leg drop jumps. All jumps were performed from a drop height of 0.18 m on to a dual force plate system. Vertical stiffness was calculated as the ratio of peak ground reaction force (GRF) to the peak center of mass (COM) displacement. Unilateral drop jumping was associated with higher GRF and greater COM displacement (both Ps < .001), but vertical stiffness was not different between tasks when considering individual limbs (P = .98). A coefficient of variation of 14.6% was observed for bilateral vertical stiffness during bilateral drop jumping; values of 6.7% and 7.6% were observed for left and right limb vertical stiffness during unilateral drop jumping. These findings suggest that unilateral drop jumps may exhibit greater reliability than bilateral drop jumps while eliciting similar vertical stiffness. It is also apparent that higher GRFs during unilateral drop jumping are mitigated by increased COM displacement.

Theoretical considerations for muscle-energy savings during distance running

We have recently demonstrated that the triceps surae muscles energy cost (EC_TS) represents a substantial portion of the total metabolic cost of running (E_run). Therefore, it seems relevant to evaluate the factors which dictate EC_TS, namely the amount and velocity of shortening, since it is likely these factors will dictate E_run. E_run and triceps surae morphological and AT mechanical properties were obtained in 46 trained and elite male and female distance runners using ultrasonography and dynamometry. EC_TS (J·stride^-1) at the speed of lactate threshold (sLT) was estimated from AT force and crossbridge mechanics and energetics. To estimate the relative impact of these factors on EC_TS, mean values for running speed, body mass, resting fascicle length (L_f), Achilles tendon stiffness and moment arm and maximum isometric plantarflexion torque were obtained. EC_TS was calculated across a range (mean ± 1 sd) of values for each independent factor. Average sLT was 233 m·min^-1. At this speed, EC_TS was 255 J·stride^-1. Estimated fascicle shortening velocity was 0.08 V_max and the level of muscle activation was 84.7% of maximum isometric torque. Compared to the EC_TS calculated from the lowest range of values obtained for each independent factor, higher AT stiffness was associated with a 39% reduction in EC_TS, 81% reduction in fascicle shortening velocity and a 31% reduction in muscle activation. Longer AT moment arms and elevated body masses were associated with an increase in EC_TS of 18% and 23%, respectively. These results demonstrate that a low EC_TS is achieved primarily from a high AT stiffness and low body mass, which is exemplified in elite distance runners.

Influence of ethnicity on vertical jump performances in male physical education students: a pilot study

BACKGROUND

The present study aimed to: 1) test the possibility of ethnic differences in squat jump (SJ), countermovement jump (CMJ) and countermovement jump with arms swing (CMJA); 2) test the possibility of ethnic differences in the effects of countermovement and arms swing; 3) verify whether the relationships between the different vertical jumps (VJ) (SJ, CMJ, CMJA) and maximal power (Pmax), determined from a force-velocity test (F-V), were dependent on the ethnicity as previously found for CMJA.

METHODS

VJ were performed by 84 active men (WAC): 40 WA and 44 C. VJ were measured on a force platform in three conditions: SJ, CMJ and CMJA. For technical reasons, only 39 of these participants (WA2C2) performed F-V test [V=V0(1-F/F0) and maximal power=0.25 V0F0]: 20 WA (WA2) and 19 C (C2).

RESULTS

There were significant ethnic differences (WA>C) in SJ, CMJ, CMJA, CMJA-CMJ, CMJA/CMJ. The effect sizes (Cohen d) of these ethnic differences were large for CMJA (0.93), CMJA-CMJ (1.11) CMJA/CMJ (0.82) and medium for CMJ (0.54) and SJ (0.56). Ethnic effect in the countermovement jump was small (Cohen d=0.04 for CMJ-SJ) and not significant.

CONCLUSIONS

For WA2C2, the slightly higher value of Pmax in WA2 (Cohen d =0.23) probably explained their slightly higher values of SJ, CMJ but not their higher values of CMJA and arms swing effect. In WA2C2, a difference in fast-fiber percentages was not the explanation of the ethnic differences because the optimal pedal rates corresponding to Pmax (0.5 V0) were similar in both groups.

Does Foot Anthropometry Predict Metabolic Cost During Running?

Several recent investigations have linked running economy to heel length, with shorter heels being associated with less metabolic energy consumption. It has been hypothesized that shorter heels require larger plantar flexor muscle forces, thus increasing tendon energy storage and reducing metabolic cost. The goal of this study was to investigate this possible mechanism for metabolic cost reduction. Fifteen male subjects ran at 16 km⋅h^-1 on a treadmill and subsequently on a force-plate instrumented runway. Measurements of oxygen consumption, kinematics, and ground reaction forces were collected. Correlational analyses were performed between oxygen consumption and anthropometric and kinetic variables associated with the ankle and foot. Correlations were also computed between kinetic variables (peak joint moment and peak tendon force) and heel length. Estimated peak Achilles tendon force normalized to body weight was found to be strongly correlated with heel length normalized to body height (r = -.751, p = .003). Neither heel length nor any other measured or calculated variable were correlated with oxygen consumption, however. Subjects with shorter heels experienced larger Achilles tendon forces, but these forces were not associated with reduced metabolic cost. No other anthropometric and kinetic variables considered explained the variance in metabolic cost across individuals.

Relationship between Achilles tendon length and running performance in well-trained male endurance runners

This study aimed to determine the relationship between Achilles tendon (AT) length and running performance, including running economy, in well-trained endurance runners. We also examined the reasonable portion of the AT related to running performance among AT lengths measured in three different portions. The AT lengths at three portions and cross-sectional area (CSA) of 30 endurance runners were measured using magnetic resonance imaging. Each AT length was calculated as the distance from the calcaneal tuberosity to the muscle-tendon junction of the soleus, gastrocnemius medialis (GM_AT ), and gastrocnemius lateralis, respectively. These AT lengths were normalized with shank length. The AT CSA was calculated as the average of 10, 20, and 30 mm above the distal insertion of the AT and normalized with body mass. Running economy was evaluated by measuring energy cost during three 4-minutes submaximal treadmill running trials at 14, 16, and 18 km/h, respectively. Among three AT lengths, only a GM_AT correlated significantly with personal best 5000-m race time (r=-.376, P=.046). Furthermore, GM_AT correlated significantly with energy cost during submaximal treadmill running trials at 14 km/h and 18 km/h (r=-.446 and -.429, respectively, P<.05 for both), and a trend toward such significance was observed at 16 km/h (r=-.360, P=.050). In contrast, there was no correlation between AT CSA and running performance. These findings suggest that longer AT, especially GM_AT , may be advantageous to achieve superior running performance, with better running economy, in endurance runners.

Running Economy from a Muscle Energetics Perspective

The economy of running has traditionally been quantified from the mass-specific oxygen uptake; however, because fuel substrate usage varies with exercise intensity, it is more accurate to express running economy in units of metabolic energy. Fundamentally, the understanding of the major factors that influence the energy cost of running (Erun) can be obtained with this approach. Erun is determined by the energy needed for skeletal muscle contraction. Here, we approach the study of Erun from that perspective. The amount of energy needed for skeletal muscle contraction is dependent on the force, duration, shortening, shortening velocity, and length of the muscle. These factors therefore dictate the energy cost of running. It is understood that some determinants of the energy cost of running are not trainable: environmental factors, surface characteristics, and certain anthropometric features. Other factors affecting Erun are altered by training: other anthropometric features, muscle and tendon properties, and running mechanics. Here, the key features that dictate the energy cost during distance running are reviewed in the context of skeletal muscle energetics.

Brain oxygenation declines in elite Kenyan runners during a maximal interval training session

PURPOSE

The purpose of this study was to characterise the cerebral oxygenation (Cox) response during a high-intensity interval training session in Kenyan runners, and to examine any relationship with running performance.

METHODS

15 Kenyan runners completed a 5-km time trial (TT) and a Fatigue Training Test on a treadmill (repeated running bouts of 1-km at a pace 5% faster than their mean 5-km TT pace with a 30-s recovery until exhaustion). Changes in Cox were monitored via near-infrared spectroscopy through concentration changes in oxy- and deoxy-haemoglobin (Δ[O₂Hb] and Δ[HHb]), tissue oxygenation index (TOI), and total hemoglobin index (nTHI).

RESULTS

The number of 1-km repetitions achieved by the participants was 5.5 ± 1.2 repetitions at a mean pace of 20.5 ± 0.7 km h^-1. Δ[O₂Hb] measured at the end of each running repetition declined progressively over the course of the trial (p = 0.01, ES = 4.59). Δ[HHb] increased during each running bout until the end of the Fatigue Training Test (p < 0.001; ES = 6.0). TOI decreased significantly from the beginning of the test (p = 0.013, ES = 1.83), whereas nTHI remained stable (ES = 0.08). The Cox decline in the Fatigue Training Test was negatively correlated with the speed at which the test was completed (p = 0.017; r = -0.61), suggesting that the best performers were able to defend their Cox better than those of lower running ability.

CONCLUSIONS

In conclusion, this study suggests that elite Kenyan runners cannot defend cerebral oxygenation when forced to exercise to their physiological limits. This emphasises the critical importance of pacing in their racing success.

Effects of ethnicity on the relationship between vertical jump and maximal power on a cycle ergometer

The aim of this study was to verify the impact of ethnicity on the maximal power-vertical jump relationship. Thirty-one healthy males, sixteen Caucasian (age: 26.3 ± 3.5 years; body height: 179.1 ± 5.5 cm; body mass: 78.1 ± 9.8 kg) and fifteen Afro-Caribbean (age: 24.4 ±2.6 years; body height: 178.9 ± 5.5 cm; body mass: 77.1 ± 10.3 kg) completed three sessions during which vertical jump height and maximal power of lower limbs were measured. The results showed that the values of vertical jump height and maximal power were higher for Afro-Caribbean participants (62.92 ± 6.7 cm and 14.70 ± 1.75 W∙kg-1) than for Caucasian ones (52.92 ± 4.4 cm and 12.75 ± 1.36 W∙kg-1). Moreover, very high reliability indices were obtained on vertical jump (e.g. 0.95 < ICC < 0.98) and maximal power performance (e.g. 0.75 < ICC < 0.97). However, multiple linear regression analysis showed that, for a given value of maximal power, the Afro-Caribbean participants jumped 8 cm higher than the Caucasians. Together, these results confirmed that ethnicity impacted the maximal power-vertical jump relationship over three sessions. In the current context of cultural diversity, the use of vertical jump performance as a predictor of muscular power should be considered with caution when dealing with populations of different ethnic origins.

Ethnicity and spatiotemporal parameters of bilateral and unilateral transtibial amputees in a 100-m sprint

Similar to able-bodied sprinters, most of the medals for the 100-m sprint in past Paralympic Games and IPC Athletics World Championships were dominated by West African (WA) and Caucasian (CC) amputee sprinters, not Asian (AS) sprinters. Although these results indicate differences in sprint performance due to ethnicity, little is known about the ethnicity and spatiotemporal parameters of the 100-m sprint for amputee sprinters. The purpose of this study was to investigate the differences in the spatiotemporal parameters of WA, CC and AS sprinters with bilateral and unilateral transtibial amputations during a 100-m sprint. We analyzed 6 WA, 28 CC, and 10 AS amputee sprinters from publicly available Internet broadcasts. For each sprinter’s run, the average speed, average step length, and step frequency were calculated by using the number of steps in conjunction with the official race time. No significant differences were found in the spatiotemporal parameters of the 100-m sprint for the WA and CC groups. On the other hand, the average speed of the AS group was significantly lower because of its shorter step length during the 100-m sprint. The results suggest that WA and CC sprinters would perform similarly during a 100-m sprint, but AS sprinters would not.

Triceps surae muscle-tendon properties in older endurance- and sprint-trained athletes

Previous studies have shown that aging is associated with alterations in muscle architecture and tendon properties (Morse CI, Thom JM, Birch KM, Narici MV. Acta Physiol Scand 183: 291–298, 2005; Narici MV, Maganaris CN, Reeves ND, Capodaglio P. J Appl Physiol 95: 2229–2234, 2003; Stenroth L, Peltonen J, Cronin NJ, Sipila S, Finni T. J Appl Physiol 113: 1537–1544, 2012). However, the possible influence of different types of regular exercise loading on muscle architecture and tendon properties in older adults is poorly understood. To address this, triceps surae muscle-tendon properties were examined in older male endurance (OE, n = 10, age = 74.0 ± 2.8 yr) and sprint runners (OS, n = 10, age = 74.4 ± 2.8 yr), with an average of 42 yr of regular training experience, and compared with age-matched [older control (OC), n = 33, age = 74.8 ± 3.6 yr] and young untrained controls (YC, n = 18, age = 23.7 ± 2.0 yr). Compared with YC, Achilles tendon cross-sectional area (CSA) was 22% ( P = 0.022), 45% ( P = 0.001), and 71% ( P < 0.001) larger in OC, OE, and OS, respectively. Among older groups, OS had significantly larger tendon CSA compared with OC ( P = 0.033). No significant between-group differences were observed in Achilles tendon stiffness. In older groups, Young's modulus was 31-44%, and maximal tendon stress 44–55% lower, than in YC ( P ≤ 0.001). OE showed shorter soleus fascicle length than both OC ( P < 0.05) and YC ( P < 0.05). These data suggest that long-term running does not counteract the previously reported age-related increase in tendon CSA, but, instead, may have an additive effect. The greatest Achilles tendon CSA was observed in OS followed by OE and OC, suggesting that adaptation to running exercise is loading intensity dependent. Achilles tendon stiffness was maintained in older groups, even though all older groups displayed larger tendon CSA and lower tendon Young's modulus. Shorter soleus muscle fascicles in OE runners may be an adaptation to life-long endurance running.

Faces and fitness: attractive evolutionary relationship or ugly hypothesis?

In recent years, various studies have attempted to understand human evolution by examining relationships between athletic performance or physical fitness and facial attractiveness. Over a wide range of five homogeneous groups (n = 327), there is an approximate 3% shared variance between facial attractiveness and athletic performance or physical fitness (95% CI = 0.5-8%, p = 0.002). Further, studies relating human performance and attractiveness often have major methodological limitations that limit their generalizability. Thus, despite statistical significance, the association between facial attractiveness and human performance has questionable biological importance. Here, we present a critique of these studies and provide recommendations to improve the quality of future research in this realm.

Reduced oxygen cost of running is related to alignment of the resultant GRF and leg axis vector: A pilot study

This pilot study investigated whether a 10-week running program (10wkRP), which reduced the oxygen cost of running, affected resultant ground reaction force (GRF), leg axis alignment, joint moment characteristics, and gear ratios. Ten novice, female runners completed a 10wkRP. Running kinematics and kinetics, in addition to oxygen consumption ( V ˙ O 2 ) during steady-state running, were recorded pre- and post-10wkRP. V ˙ O 2 decreased (8%) from pre-10wkRP to post-10wkRP. There was a better alignment of the resultant GRF and leg axis at peak propulsion post-10wkRP compared with pre-10wkRP (10.8 ± 4.9 vs 1.6 ± 1.2°), as the resultant GRF vector was applied 7 ± 0.6° (P = 0.008) more horizontally. There were shorter external ankle moment arms (24%) and smaller knee extensor moments (23%) at peak braking post-10wkRP. The change in V ˙ O 2 was associated with the change in alignment of the resultant GRF and leg axis (rs  = 0.88, P = 0.003). As runners became more economical, they exhibited a more aligned resultant GRF vector and leg axis at peak propulsion. This appears to be a self-optimization strategy that may improve performance. Additionally, changes to external ankle moment arms indicated beneficial low gear ratios were achieved at the time of peak braking force.