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PHYSIOLOGICAL AREA   

Medicina dello Sport 2018 September;71(3):323-35

DOI: 10.23736/S0025-7826.18.03323-9

Copyright © 2018 EDIZIONI MINERVA MEDICA

language: English, Italian

Changes in knee extensor muscle contractile properties after cycling at constant intensity

Laura LEPASALU , Jaan ERELINE, Helena GAPEYEVA, Mati PÄÄSUKE

Institute of Sport Sciences and Physiotherapy, University of Tartu, Tartu, Estonia


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BACKGROUND: The present study evaluated isometric twitch contractile properties of knee extensor (KE) muscles before and after 30-min cycling exercise at constant intensity (250 W) in laboratory conditions.
METHODS: Ten male road cyclists (aged 20-30 years) participated. Isometric maximal voluntary contraction (MVC) force and electrically evoked isometric twitch contraction characteristics of the KE muscle were measured by percutaneous electrical nerve stimulation before and immediately after, 15 min and 30 min after cycling exercise. The percentage increase in twitch contraction force after a 5” isometric MVC in relation to resting twitch was taken as an indicator of capacity for PAP.
RESULTS: A significant decrease (P=0.001) in isometric MVC force and twitch maximal rates of force development and relaxation, PAP, and a prolongation in twitch half-relaxation time (HRT) were found immediately after the end of cycling exercise. There were no significant exercise-induced changes in twitch peak force and contraction time. The post-exercise recovery occurred for twitch HRT, PAP and maximal rates of force development and relaxation in 30 min, while MVC force remained significantly reduced.
CONCLUSIONS: We concluded that after 30-min cycling exercise at constant intensity in KE muscles, the capacity for maximal voluntary force generation was decreased and a marked peripheral fatigue emerged, expressed by decrease in the rates of electrically evoked twitch force generation and relaxation; electrically evoked twitch force characteristics recovered faster after exercise compared to voluntary force capacity of KE muscle.


KEY WORDS: Bicycling - Fatigue - Exercise

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