Journal of Sports Science and Medicine
Journal of Sports Science and Medicine
ISSN: 1303 - 2968   
Ios-APP Journal of Sports Science and Medicine
Androit-APP Journal of Sports Science and Medicine
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©Journal of Sports Science and Medicine ( 2016 ) 15 , 697 - 703

Research article
Low-Frequency Fatigue Assessed as Double to Single Twitch Ratio after Two Bouts of Eccentric Exercise of the Elbow Flexors
Damian Janecki , Anna Jaskólska, Jarosław Marusiak, Artur Jaskólski
Author Information
Department of Kinesiology, Faculty of Physiotherapy, University School of Physical Education, Wroclaw, Poland

Damian Janecki
✉ Department of Kinesiology, Faculty of Physiotherapy, University School of Physical Education, Wroclaw, Poland, 51-612 Wroclaw, Al. Paderewskiego 35, Building P4
Email: damidj@poczta.fm
Publish Date
Received: 30-06-2016
Accepted: 08-11-2016
Published (online): 01-12-2016
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ABSTRACT

The aim of this study was to assess low-frequency fatigue as a double to single twitch ratio after repeated eccentric exercise of the elbow flexors. Maximal isometric torque, single and double twitch responses and low-frequency fatigue were assessed on the elbow flexors in 16 untrained male volunteers before, immediately after, 24 and 48 hours following two bouts of eccentric exercise consisted of 30 repetitions of lowering a dumbbell adjusted to ~75% of each individual’s maximal isometric torque. Maximal isometric torque and electrically evoked responses decreased significantly in all measurements after the first bout of eccentric exercise (p < 0.05). In measurements performed at 24 and 48 hours after the second bout both maximal voluntary isometric torque and electrically evoked contractions were significantly higher than in measurements performed after the first bout (p < 0.05). Although low-frequency fatigue significantly increased up to 48 hours after each bout of eccentric exercise, its values at 24 and 48 hours after the second bout were significantly lower than at respective time points after the first bout (p < 0.05). Double to single twitch ratio could be used as a sensitive tool in the evaluation of muscle recovery and adaptation to repeated eccentric exercise.

Key words: Biceps brachii, electrical stimulation, lenghtening action, repeated bout effect


           Key Points
  • First bout of eccentric (ECC) exercise of the elbow flexors muscles induced repeated bout effect that lead to faster recovery of the low-frequency fatigue, the maximal torque of voluntary and electrically evoked contractions, and smaller soreness sensation, when the exercise are repeated 2-3 weeks later.
  • Double (DT) to single twitch (ST) ratio could be used as a sensitive tool in the evaluation of muscle recovery and adaptation to repeated eccentric exercise.
  • The single twitch and DT to ST ratios seem to be more susceptible for minimal force deficits that could occur even after repeated ECC where repeated bout effect should confer the protection after subsequent muscle damage.
 
 
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