Document Detail


Evidence for neuromuscular fatigue during high-intensity cycling in warm, humid conditions.
MedLine Citation:
PMID:  11394239     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The purpose of this study was to examine and describe the neuromuscular changes associated with fatigue using a self-paced cycling protocol of 60-min duration, under warm, humid conditions. Eleven subjects [mean (SE) age 21.8 (0.8) years; height 174.9 (3.0) cm; body mass 74.8 (2.7) kg; maximum oxygen consumption 50.3 (1.8) ml.kg.min-1] performed one 60-min self-paced cycling time trial punctuated with six 1-min "all out" sprints at 10-min intervals, while 4 subjects repeated the trial for the purpose of determining reproducibility. Power output, integrated electromyographic signal (IEMG), and mean percentile frequency shifts (MPFS) were recorded at the mid-point of each sprint. There were no differences between trials for EMG variables, distance cycled, mean heart rate, and subjective rating of perceived exertion for the subjects who repeated the trial (n = 4). The results from the repeated trials suggest that neuromuscular responses to self-paced cycling are reproducible between trials. The mean heart rate for the 11 subjects was 163.6 (0.71) beats.min-1. Values for power output and IEMG expressed as a percentage of that recorded for the initial sprint decreased during sprints 2-5, with normalised values being 94%, 91%, 87% and 87%, respectively, and 71%, 71%, 73%, and 77%, respectively. However, during the final sprint normalised power output and IEMG increased to 94% and 90% of initial values, respectively. MPFS displayed an increase with time; however, this was not significant (P = 0.06). The main finding of this investigation is the ability of subjects to return power output to near initial values during the final of six maximal effort sprints that were included as part of a self-paced cycling protocol. This appears to be due to a combination of changes in neuromuscular recruitment, central or peripheral control systems, or the EMG signal itself. Further investigations in which changes in multiple physiological systems are assessed systematically are required so that the underlying mechanisms related to the development of fatigue during normal dynamic movements such as cycling can be more clearly delineated.
Authors:
D Kay; F E Marino; J Cannon; A St Clair Gibson; M I Lambert; T D Noakes
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  European journal of applied physiology     Volume:  84     ISSN:  1439-6319     ISO Abbreviation:  Eur. J. Appl. Physiol.     Publication Date:    2001 Jan-Feb
Date Detail:
Created Date:  2001-06-07     Completed Date:  2001-10-18     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  100954790     Medline TA:  Eur J Appl Physiol     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  115-21     Citation Subset:  IM    
Affiliation:
Human Movement Studies Unit and Human Performance Laboratory, Charles Sturt University, Bathurst NSW 2795, Australia.
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MeSH Terms
Descriptor/Qualifier:
Adolescent
Adult
Bicycling / physiology*
Body Temperature / physiology
Electromyography
Female
Hot Temperature*
Humans
Humidity / adverse effects*
Male
Muscle Fatigue / physiology*
Muscle, Skeletal / innervation,  physiology

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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