Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

Abstract

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.

DOI： 10.1186/s40101-023-00326-3

researchmap

Other Link： https://link.springer.com/article/10.1186/s40101-023-00326-3/fulltext.html

Authorship：Lead author   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1111/apha.13821

researchmap

Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1111/apha.13821

Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1007/s40279-022-01651-w

researchmap

Other Link： https://link.springer.com/article/10.1007/s40279-022-01651-w/fulltext.html

Publishing type：Research paper (scientific journal)   Publisher：Frontiers Media SA  

This study investigated the sex influence on the acute and delayed fatigue effects of a 20 km graded running race. Eighteen recreational runners, 10 women and 8 men, completed the race. The testing protocol included five sessions: a week before the race (PRE), 35 ± 15 min after (POST), 2 h, 2 and 4 days (2D and 4D) later. Each session included uni- and bilateral maximal isometric voluntary contractions of the knee extensors (MVC), a squat jump (SJ), and a drop jump (DJ). Acute and delayed muscle soreness (DOMS) were evaluated for the quadriceps, hamstring and triceps surae muscle groups. The 2D and 4D sessions included also a horizontal force-velocity test (HF-V) performed under five resistive conditions. For each test, a set of key variables was computed to characterize the lower limb functional recovery. Mixed ANOVA analyses revealed significant (sex × time) interactions, with larger acute drops for men in MVCs and earlier recovery for women in the bilateral MVC (p < 0.001) and DJ (p < 0.05) tests. Only women reported DOMS for the hamstrings at 2D (p < 0.001) and showed small improvements in pure concentric SJ (p < 0.05) and HF-V (p < 0.01) tests at 4D. As expected, DOMS disappeared prior to the complete functional recovery. These results confirmed the combined influence of testing task and sex on the functional recovery pattern while supporting a lesser and faster recovery in women. The originality of this study lies in the complexity and sex-dependence of the functional recovery pattern revealed by a multiple factorial analysis which was used to identify the most discriminating tests and variables in the recovery pattern. The obtained clusters highlighted some recovery profiles associated with greater risks of injury when starting to run again. However, the lack of sex × time interaction for normalized values emphasizes the major influence of men’s initially higher functional values compared to women.

DOI： 10.3389/fphys.2021.649396

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Frontiers Media SA  

This study aimed to simultaneously examine the differences of human nerve conduction velocity (NCV) and nerve cross-sectional area (nCSA) between the upper and lower limbs and between different regions of the upper and lower limbs. Thirty healthy subjects volunteered for the study. NCV and nCSA of the ulnar and tibial nerves were measured with the dominant and non-dominant arms and the supporting and reacting legs using supramaximal electric stimulation and peripheral nerve ultrasonography at three regions for ulnar and tibial nerves, respectively. Supramaximal electric stimulation was superficially applied to the ulnar and tibial nerves at each point. These action potentials were recorded from the digiti minimi and soleus muscles for the ulnar and tibial nerves, respectively. Our results clearly showed that the NCV, nCSA, and circumference of the ulnar and tibial nerves were higher and greater in the lower limbs than in the upper limbs. The greater the circumference, the greater the nCSA for both the upper and lower limbs. However, unlike the upper limbs, the supporting leg did not have higher NCV than the reacting leg despite its greater circumference. Therefore, nCSA can be related to the circumference but not necessarily function for NCV developments of the lower limbs. These various aspects between the upper and lower limbs suggest that NCV does not depend on the nCSA sizes or upper and lower limb circumference; the results indicate the existence of limb-specific NCV but not nCSA developments.

DOI： 10.3389/fphys.2020.609006

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

Walking and running are mechanically and energetically different locomotion modes. For selecting one or another, speed is a parameter of paramount importance. Yet, both are likely controlled by similar low-dimensional neuronal networks that reflect in patterned muscle activations called muscle synergies. Here, we challenged human locomotion by having our participants walk and run at a very broad spectrum of submaximal and maximal speeds. The synergistic activations of lower limb locomotor muscles were obtained through decomposition of electromyographic data via non-negative matrix factorization. We analyzed the duration and complexity (via fractal analysis) over time of motor primitives, the temporal components of muscle synergies. We found that the motor control of high-speed locomotion was so challenging that the neuromotor system was forced to produce wider and less complex muscle activation patterns. The motor modules, or time-independent coefficients, were redistributed as locomotion speed changed. These outcomes show that humans cope with the challenges of high-speed locomotion by adapting the neuromotor dynamics through a set of strategies that allow for efficient creation and control of locomotion.

DOI： 10.1016/j.heliyon.2020.e05377

PubMed

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ADIS INT LTD  

Background Patients who have had an Achilles tendon (AT) rupture repaired are potentially at higher risk for re-rupture than those without previous rupture. Little attention has been given to the neuromechanical modulation of muscle-tendon interaction and muscle activation profiles during human dynamic movements after AT rupture repair.
Objective The purpose of this study was to examine muscle-tendon behavior and muscle activation during bilateral hopping.
Methods We enrolled nine subjects who had undergone surgical repair of unilateral AT rupture within the past 1-2 years. Subjects performed bilateral hopping while we took ultrasound, kinematic, and electromyogram recordings and measurements. AT behaviors were also recorded. We then compared responses between values obtained from the ruptured AT leg (LEG(ATR)) and non-ruptured AT leg (LEG(NOR)).
Results During hopping, the AT stretching amplitudes were greater in the LEG(ATR) than in the LEG(NOR), although the peak AT force and stiffness were smaller in the LEG(ATR) than in the LEG(NOR). The AT negative mechanical work did not show any significant differences between both legs. However, positive works were significantly lower in the LEG(ATR) than in the LEG(NOR). Electromyogram patterns in both soleus and tibialis anterior muscles clearly differed after ground contact for the LEG(ATR) and the LEG(NOR).
Conclusions These results suggest that the repaired ruptured AT can be compliant and have insufficient Young's modulus, which can influence mechanical responses in muscle activities. The modulation of agonist-antagonist muscle activities corresponding to the different levels of stiffness between the LEG(ATR) and the LEG(NOR) may not be fully functioning during the pre-activation phase.

DOI： 10.1007/s40279-016-0629-3

Web of Science

PubMed

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：(一社)日本体育学会  

中段の構えで剣道を行っている小学生から成人の男性剣道実践者65名と、一般男子大学生20名(一般成人)を対象に、アキレス腱と腓腹筋の形態の左右差について調査を行った。剣道実践者は、剣道経験年数で初心者群(平均経験年数3年)22名、中堅者群(平均経験年数8年)21名、熟練者群(平均経験年数16年)22名に振り分けた。熟練剣道実践者ほどアキレス腱の形態(長さや太さ)の左右差が大きく、一般成人より剣道実践者の蹴り脚において、アキレス腱は細く、その組織スティフネスが低いという結果が得られた。特に剣道実践者における蹴り脚のアキレス腱組織の材質(スティフネスとヤング率)の低さは、剣道の動作やトレーニングの経験年数と関係する可能性があり、剣道実践者における蹴り脚のアキレス腱断裂の生じやすさに影響を及ぼしていると考えられた。左右脚で異なる剣道特有の動作やそのトレーニング経験によって、左右差が大きくなっていることが示唆された。

DOI： 10.5432/jjpehss.16012

researchmap

Other Link： https://search.jamas.or.jp/index.php?module=Default&action=Link&pub_year=2016&ichushi_jid=J00793&link_issn=&doc_id=20161229170002&doc_link_id=10.5432%2Fjjpehss.16012&url=https%3A%2F%2Fdoi.org%2F10.5432%2Fjjpehss.16012&type=J-STAGE&icon=https%3A%2F%2Fjk04.jamas.or.jp%2Ficon%2F00007_3.gif

Language：Japanese  

J-GLOBAL

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Leg muscle activation profiles and muscle-tendon interaction were studied with eleven internationally high-level Kenyan and eleven national level Japanese distance runners.
Ultrasonography and kinematics were applied together with surface electromyography (EMG) recordings of leg muscles when subjects ran on treadmill at 9.0 (SLOW) and 13.9 km h(-1) (MEDIUM).
At each speed, both groups presented similar contact and flight times. The kinematic and ultrasound analyses revealed that, in contrast to the Japanese runners, the Kenyans demonstrated during contact smaller stretching and shortening amplitudes (p < 0.01) of the tendinous tissue of medial gastrocnemius (MG), but greater tendon contribution to the muscle-tendon unit shortening (p < 0.05). The MG fascicles of the Kenyans were shorter not only at the resting standing position, but also during the contact phase at both running speeds (p < 0.01). The EMG profiles of the Kenyans showed lower braking/preactivation ratio in both MG and tibialis anterior (p < 0.05) muscles. They were also characterized by negative relationships between the Achilles tendon moment arm and the MG fascicle shortening during contact (r = -0.54, p < 0.01). In contrast, the Japanese presented the classical stretch-shortening cycle muscle activation profile of relatively high MG EMG activity during the braking phase.
These findings provide new suggestions that the Kenyans have unique structural characteristics which can result in the reduction of muscle and tendinous stretch-shortening loading together with smaller muscle activation during contact at submaximal running speed.

DOI： 10.1007/s00421-014-3067-7

Web of Science

PubMed

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japanese Society of Physical Fitness and Sports Medicine  

The purpose of the present study was to examine the importance of the agonist muscle activity of the post-impact 30 ms phase during drop jump (DJ) for effective rebound performance by comparing those of sprint runners and swimmers. The eight sprint runners (SPRINT) and twelve swimmers (SWIM) were participated in this study. They performed DJ from a 0.3-m height box with maximal rebound efforts. Electromyograms (EMG) of the lower leg muscles (medial gastrocnemius [MG], soleus [SOL] and tibialis anterior [TA]), and vertical ground reaction force together with kinematic data were measured simultaneously during DJ. In addition, the onsets of fascicle stretching of the MG and SOL muscles were measured by using high-speed ultrasonography (521Hz) during DJ. The onsets of the fascicle stretching of SOL during DJ were not significantly different between SPRINT and SWIM (15 ± 7 ms and 16 ± 6 ms, respectively). During DJ, SPRINT showed onset of the SOL EMG before the ground contact (-26 ± 19 ms). Meanwhile, SWIM showed the onset of the SOL EMG after the ground contact of DJ (16 ± 19 ms). These results suggest that the SOL muscles for SWIM cannot be fully-activated during the braking phase. Consequently, the rate of force development during the braking phase of DJ and subsequently rebound height could be reduced in SWIM.

DOI： 10.7600/jspfsm.64.165

Scopus

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：大阪体育学会  

researchmap

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

The Achilles tendon moment arm (MA_ AT) and foot lever ratio (FLR) can play important roles for force production and movement economy during locomotion. This notion has become more relevant, and suggestion has been given that the Kenyan runners belonging to the world elite would have specific anatomical, mechanical, and functional properties in their lower limbs and that this feature could be responsible for their high running economy. The present study aimed to characterize the AT of elite Kenyan distance runners as compared with Japanese ones, and to examine the potential relationship with their running performance. Ultrasonography was used to measure AT cross-sectional area and AT soleus and gastrocnemius lengths. MA_ AT and FLR were calculated from the position of anatomical landmarks using sagittal plane photographs. MA_ AT was significantly longer and the FLR lower in Kenyans than in Japanese. Independently of the group, the running performance was positively related to the MA_ AT (r = 0.55, P < 0.001) and negatively to the FLR (r = -0.45, P = 0.002). These results suggest that longer MA_ AT and lower FLR could be advantageous in elite Kenyan runners, by contributing to effective endurance running performance in a protective and economical way.

DOI： 10.1111/sms.12161

Web of Science

researchmap

Language：English   Publisher：The Japanese Society of Physical Fitness and Sports Medicine  

The superior success of East-African endurance runners has stimulated a large amount of interest in exploring valid reasons for their performance, especially for neuromuscular mechanics. This review provides a brief overview of classic neuromuscular interaction during running; and, thereafter, describes a specific neuromuscular interaction alternative to the classic stretch-shortening cycle concept for enhancing the running economy of East-African distance runners.

DOI： 10.7600/jpfsm.2.361

CiNii Article

CiNii Books

researchmap

Other Link： https://jlc.jst.go.jp/DN/JALC/10023205641?from=CiNii

Language：Japanese   Publisher：一般社団法人 日本体育学会  

DOI： 10.20693/jspehss.66.200_2

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：一般社団法人 日本体育学会  

DOI： 10.20693/jspehss.66.195_2

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：一般社団法人 日本体育学会  

CiNii Article

researchmap

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

The exploration of muscle mechanics during natural human locomotion is a continuous challenge. Ultrasonography is a technique, which can be used to study the fascicle and tendon length changes during movements. However, many of the ealier studies were unable to precisely identify how the fascicles behave in different muscles. This may have caused misleading generalizations. In addition, because the muscle spindles are located inside the contractile tissue, it is important to determine the role that stretch reflexes may play during rapid and intensive dynamic movements. Brightness mode ultrasonography has revealed that, in human locomotion, the nature of fascicle and tendon length changes varies depending on the task, contraction intensity, and the muscles involved. The findings emphasize that the active fascicles of the gestrocnemius muscle are suddenly stretched, although they are shortening. This short-lasting stretch triggers the stretch reflex, timing of which is dependent on running speed.

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：一般社団法人 日本体育学会  

DOI： 10.20693/jspehss.65.157_3

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：日本バイオメカニクス学会事務局  

CiNii Article

CiNii Books

researchmap

Language：Japanese  

CiNii Article

CiNii Books

researchmap

Other Link： http://search.jamas.or.jp/link/ui/2013243375

Language：Japanese   Publisher：一般社団法人 日本体育学会  

DOI： 10.20693/jspehss.64.214_1

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publisher：一般社団法人 日本体育学会  

DOI： 10.20693/jspehss.64.199_2

CiNii Article

CiNii Books

researchmap

J-GLOBAL

researchmap

J-GLOBAL

researchmap

J-GLOBAL

researchmap