European Journal of Applied Physiology

, Volume 115, Issue 4, pp 849–859 | Cite as

Can measures of muscle–tendon interaction improve our understanding of the superiority of Kenyan endurance runners?

  • Kanae SanoEmail author
  • Caroline Nicol
  • Masanobu Akiyama
  • Yoko Kunimasa
  • Toshiaki Oda
  • Akira Ito
  • Elio Locatelli
  • Paavo V. Komi
  • Masaki Ishikawa
Original Article



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.


Ultrasonography Muscle–tendon interaction Endurance running Kenya 



Averaged EMG


Surface electromyogram


Integrated EMG


Achilles tendon moment arm


Medial gastrocnemius


MG fascicle length


MG muscle–tendon unit length


MG tendinous tissues length


Muscle–tendon unit




Stretch-shortening cycle


Tibialis anterior



The authors would like to acknowledge Mr. Kipchoge Keino and the IAAF High Performance Training Centre, Kenya for helping recruitments of subjects and providing measurement place. Also, the authors thank Mr. Julian Wayne for checking the English language. This work was supported by MEXT/JSPS KAKENHI Grant Number 20800061, 23700756, 23500729 and 26702026.

Conflict of interest

No conflict of interests declared.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  • Kanae Sano
    • 1
    Email author
  • Caroline Nicol
    • 2
    • 3
  • Masanobu Akiyama
    • 1
  • Yoko Kunimasa
    • 1
  • Toshiaki Oda
    • 4
  • Akira Ito
    • 1
  • Elio Locatelli
    • 5
  • Paavo V. Komi
    • 6
  • Masaki Ishikawa
    • 1
  1. 1.Osaka University of Health and Sport ScienceOsakaJapan
  2. 2.CNRS, UMR 7287Aix-Marseille UniversitéMarseilleFrance
  3. 3.Norwegian School of Sport ScienceOsloNorway
  4. 4.Hyogo University of Teacher EducationKatōJapan
  5. 5.International Association of Athletics FederationsMonacoMonaco
  6. 6.NMRC and Likes Research CenterUniversity of JyväskyläJyväskyläFinland

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