title: Increases in M-wave latency of biceps brachii after elbow flexor eccentric contractions in women.
abstract: OBJECTIVE
  Eccentric contractions (ECCs) induce muscle damage that is indicated by prolonged loss of muscle function and delayed onset muscle soreness. It is possible that ECCs affect motor nerves, and this may contribute to the prolonged decreases in force generating capability. The present study investigated the hypothesis that M-wave latency of biceps brachii would be increased after maximal elbow flexor ECCs resulting in prolonged loss of muscle strength.
  
  
  METHODS
  Fifteen women performed exercise consisting of 60 maximal ECCs of the elbow flexors using their non-dominant arm. M-wave latency was assessed by the time taken from electrical stimulation applied to the Erb's point to the onset of M-wave of the biceps brachii before, immediately after, and 1-4 days after exercise. Maximal voluntary isometric contraction (MVC) torque, range of motion (ROM) and muscle soreness using a numerical rating scale were also assessed before and after exercise.
  
  
  RESULTS
  Prolonged decreases in MVC torque (1-4 days post-exercise: -54 to -15 %) and ROM (1-2 days: -32 to -22 %), and increased muscle soreness (peak: 4.2 out of 10) were evident after exercise (p < 0.05). The M-wave latency increased (p < 0.01) from 5.8 ± 1.0 ms before exercise to 6.5 ± 1.7 ms at 1 day and 7.2 ± 1.5 ms at 2 days after exercise for the exercised arm only. No significant changes in M-wave amplitude were evident after exercise.
  
  
  CONCLUSIONS
  The increased M-wave latency did not fully explain the prolonged decreases in MVC torque after eccentric exercise, but may indicate reversible motor nerve impairment.
authors.affiliation: Graduate School of Health and Sport Science, Nippon Sport Science University, 7-1-1, Fukasawa, Setagaya, Tokyo, 158-8508, Japan. kouzaki.karina@gmail.com.
authors.forename: Karina
authors.initials: K
authors.lastname: Kouzaki
authors.affiliation: Centre for Exercise and Sports Science Research, School of Medical and Health Sciences, Edith Cowan University, 270 Joondalup Drive, Joondalup, WA, 6027, Australia.
authors.forename: Kazunori
authors.initials: K
authors.lastname: Nosaka
authors.affiliation: Graduate School of Education, Okayama University, 3-1-1, Tsushimanaka, Kita, Okayama, 700-8530, Japan.
authors.forename: Eisuke
authors.initials: E
authors.lastname: Ochi
authors.affiliation: Graduate School of Health and Sport Science, Nippon Sport Science University, 7-1-1, Fukasawa, Setagaya, Tokyo, 158-8508, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Nakazato
mesh_terms: D000328:Adult; D001132:Arm / Q000502:physiology*; D004550:Elbow / Q000502:physiology*; D004551:Elbow Joint / Q000502:physiology; D004558:Electric Stimulation / Q000379:methods; D004576:Electromyography / Q000379:methods; D015444:Exercise / Q000502:physiology; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D063806:Myalgia / Q000503:physiopathology; D016059:Range of Motion, Articular / Q000502:physiology; D019415:Torque; D055815:Young Adult
keywords: Biceps brachii; Erb’s point; M-wave; Muscle damage; Nerve damage