Eccentric contraction–induced muscle damage in human flexor pollicis brevis is accompanied by impairment of motor nerve

• Published in: Scandinavian journal of medicine & science in sports Vol. 30; no. 3; pp. 462 - 471
• Main Authors: Ochi, Eisuke, Ueda, Hisashi, Tsuchiya, Yosuke, Kouzaki, Karina, Nakazato, Koichi
• Format: Journal Article
• Language: English
• Published: Denmark Blackwell Publishing Ltd 01-03-2020
• Subjects: Adolescent; electrical stimulation; Humans; lengthening contraction; Male; median nerve; Motor Neurons - pathology; Muscle Contraction; Muscle Strength Dynamometer; Muscle, Skeletal - physiopathology; Myalgia; M‐wave; nerve function; Neural Conduction; Range of Motion, Articular; strength loss; Torque; Young Adult; electrical stimulation; median nerve; nerve function; M-wave; lengthening contraction; strength loss
• ISSN: 0905-7188; 1600-0838
• DOI: 10.1111/sms.13589

Background
Eccentric contractions (ECCs) cause muscle damage. In addition, we showed that ECCs induce nerve dysfunction and damage with rats and human.
Purpose
We aimed to evaluate motor nerve conduction velocity (MCV) for flexor pollicis brevis muscle (FPBM) after ECCs.
Methods
Twelve men (years, 19.8 ± 1.7 years; height, 172.4 ± 7.0 cm; weight, 64.0 ± 8.6 kg) performed maximal 100 ECCs on their FPBM of non‐dominant hands with torque dynamometer. The dominant hands were control (CON). Maximal voluntary contraction (MVC), range of motion (ROM), DOMS, and MCV were assessed before, immediately post, and 1, 2, and 5 days after ECCs. MCV was calculated as the distance by stimulation divided by the latencies of the waveforms generated. Values were statistically analyzed by two‐way ANOVA, and the significance level was set at P < .05.
Results
Decreases in MVC immediately (−32.9%) to 5 days after ECCs were significantly greater (P < .05) than for the CON group. ROM showed a significant decrease immediately (−21.6%) after ECCs compared with before ECCs and CON group (P < .05). DOMS after ECCs increased at 1 and 2 days (5.0 cm) after ECCs compared with before ECCs and CON (P < .05). Also, MCV after ECCs delayed significantly from immediately (−36.4%), 1, 2, and 5 days after ECCs compared with CON (P < .05), while no significant change in M‐wave amplitude was observed over time for both ECCs and CON.
Conclusion
The present study showed that ECCs of the FPBM cause a significant delay in MCV of median nerve.