ORIGINAL ARTICLE  EXERCISE PHYSIOLOGY AND BIOMECHANICS 

The Journal of Sports Medicine and Physical Fitness 2019 July;59(7):1097-101

DOI: 10.23736/S0022-4707.18.09102-8

Copyright © 2018 EDIZIONI MINERVA MEDICA

language: English

Muscular recruitment is associated with muscular function and swelling following eccentric contractions of human elbow flexors

Yosuke TSUCHIYA ¹, Hisashi UEDA ², Eisuke OCHI ³ ✉

¹ Faculty of Modern Life, Teikyo Heisei University, Nakano, Tokyo, Japan; ² Faculty of Health and Medical Science, Teikyo Heisei University, Uruidominami, Ichihara, Chiba, Japan; ³ Faculty of Bioscience and Applied Chemistry, Hosei University, Kajino, Koganei, Tokyo, Japan

BACKGROUND: This study investigated the relationship between muscle fiber recruitment and the magnitude of muscle damage by isotonic eccentric contractions (ECCs).
METHODS: Ten healthy men (age: 27.2±6.0 y, height: 174. 0±5.3 cm, body mass 70.1±2.1 kg) were recruited in this study. Subjects performed 30 ECCs of the elbow flexors using a dumbbell adjusted to 40% and 80% one repetition maximum of each individual. The dependent variables maximal voluntary isometric contraction (MVC) torque, Range of Motion (ROM), delayed onset muscle soreness (DOMS), cross-sectional area (CSA) and transverse relaxation time (T2) of magnetic resonance imaging (MRI) were measured immediately before, immediately after and 1, 3, and 5 days after each exercise.
RESULTS: The decreased MVC and limited ROM were significantly greater for 80% than that 40% (P<0.05) at immediately after ECCs. However, no significant difference between 40% and 80% was found for DOMS. CSA at 5 days after ECCs was significantly higher 80% (P<0.05) than 40% (P<0.05). No significant changes in post T2 (acute T2) was found for 40%, but an increased acute T2 was observed in 80% (P<0.05). We found a significant correlation between the change in T2 at immediately after and MVC at immediately after (r=0.77, P<0.05). In addition, a significant correlation between the change in T2 at immediately after and change in CSA at 3 days after (r=-0.83, P<0.05) was found.
CONCLUSIONS: We conclude that the muscle strength loss and swelling following ECCs are related to the muscle fiber recruitment.

KEY WORDS: Isotonic contraction; Muscle; Edema