Relationship between neuromuscular fatigue, muscle activation and the work done above the critical power during severe‐intensity exercise

New Findings What is the central question of this study? Does the work done above critical power (W′) or muscle activation determine the degree of peripheral fatigue induced by cycling time trials performed in the severe‐intensity domain? What is the main finding and its importance? Peripheral fatig...

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Bibliographic Details
Published in:Experimental physiology 2022-04, Vol.107 (4), p.312-325
Main Authors: Ducrocq, Guillaume P., Blain, Grégory M.
Format: Article
Language:English
Subjects:
critical power
Electrical stimuli
Electromyography
Exercise - physiology
exercise performance
Exercise Tolerance - physiology
Fatigue
Female
Human health and pathology
Humans
Life Sciences
Male
muscle activation
Muscle contraction
Muscle Contraction - physiology
Muscle Fatigue - physiology
Muscle, Skeletal - physiology
neuromuscular fatigue
Quadriceps muscle
Quadriceps Muscle - physiology
recovery from fatigue
Tissues and Organs
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Summary:New Findings What is the central question of this study? Does the work done above critical power (W′) or muscle activation determine the degree of peripheral fatigue induced by cycling time trials performed in the severe‐intensity domain? What is the main finding and its importance? Peripheral fatigue increased when power output and muscle activation increased, whereas W′ did not change between the time trials. Therefore, no relationship was found between W′ and exercise‐induced peripheral fatigue such as previously postulated in the literature. In contrast, we found a significant association between EMG amplitude during exercise and exercise‐induced reduction in the potentiated quadriceps twitch, suggesting that muscle activation plays a key role in determining peripheral fatigue during severe‐intensity exercise. In order to determine the relationship between peripheral fatigue, muscle activation and the total work done above critical power (W′), 10 men and four women performed, on separated days, self‐paced cycling time trials of 3, 6, 10 and 15 min. Exercise‐induced quadriceps fatigue was quantified using pre‐ to postexercise (15 s to 15 min recovery) changes in maximal voluntary contraction (MVC) peak force, voluntary activation and potentiated twitch force (QT). Voluntary activation was measured using the interpolated twitch technique, and QT was evoked by electrical stimulations of the femoral nerve. Quadriceps muscle activation was determined using the root mean square of surface EMG of vastus lateralis (VLRMS), vastus medialis (VMRMS) and rectus femoris (RFRMS). Critical power and W′ were calculated from the power–duration relationship from the four time trials. Mean power output and mean VLRMS, VMRMS and RFRMS were greater during shorter compared with longer exercise periods (P 
ISSN:0958-0670
1469-445X
DOI:10.1113/EP090043