ORIGINAL ARTICLE  EXERCISE PHYSIOLOGY AND BIOMECHANICS 

The Journal of Sports Medicine and Physical Fitness 2018 May;58(5):622-9

DOI: 10.23736/S0022-4707.17.06890-6

Copyright © 2017 EDIZIONI MINERVA MEDICA

language: English

Is the stiffness of human muscle and tendon structures related to muscle fiber composition in vivo?

Keitaro KUBO ¹ ✉, Daisuke MIYAZAKI ², Hideaki YATA ³, Shozo SHIMOJU ², Masaji OKADA ², Naoya TSUNODA ²

¹ Department of Life Science, The University of Tokyo, Meguro, Tokyo, Japan; ² Faculty of Physical Education, Kokushikan University, Tokyo, Japan; ³ Sports Science Laboratory, Wako University, Machida, Tokyo, Japan

BACKGROUND: The aim of the present study was to investigate the relationship between estimated muscle fiber composition (time-to-peak twitch torque; TPT) and muscle stiffness under passive and active conditions as well as stiffness of tendon structures in human plantar flexors.
METHODS: TPT was assessed using supramaximal electrical stimulation. Active muscle stiffness in the medial gastrocnemius muscle was calculated based on changes in estimated muscle force and fascicle length during fast stretching after 50% maximal isometric contractions. Passive muscle stiffness was also calculated from estimated passive muscle force and fascicle length during slow passive stretching. Stiffness of tendon structures was determined during isometric plantar flexion using ultrasonography.
RESULTS: TPT did not correlate with passive muscle stiffness (r=0.039, P=0.790), active muscle stiffness (r=0.185, P=0.203), or stiffness of tendon structures (r=-0.178, P=0.477).
CONCLUSIONS: These results suggested that the muscle fiber composition of the human medial gastrocnemius muscle was not related to the mechanical properties of muscles or tendon structures.

KEY WORDS: Tendons - Muscle, skeletal - Ultrasonography