Document Detail


Mechanisms of aerobic performance impairment with heat stress and dehydration.
MedLine Citation:
PMID:  20689090     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Environmental heat stress can challenge the limits of human cardiovascular and temperature regulation, body fluid balance, and thus aerobic performance. This minireview proposes that the cardiovascular adjustments accompanying high skin temperatures (T(sk)), alone or in combination with high core body temperatures (T(c)), provide a primary explanation for impaired aerobic exercise performance in warm-hot environments. The independent (T(sk)) and combined (T(sk) + T(c)) effects of hyperthermia reduce maximal oxygen uptake (Vo(2max)), which leads to higher relative exercise intensity and an exponential decline in aerobic performance at any given exercise workload. Greater relative exercise intensity increases cardiovascular strain, which is a prominent mediator of rated perceived exertion. As a consequence, incremental or constant-rate exercise is more difficult to sustain (earlier fatigue) or requires a slowing of self-paced exercise to achieve a similar sensation of effort. It is proposed that high T(sk) and T(c) impair aerobic performance in tandem primarily through elevated cardiovascular strain, rather than a deterioration in central nervous system (CNS) function or skeletal muscle metabolism. Evaporative sweating is the principal means of heat loss in warm-hot environments where sweat losses frequently exceed fluid intakes. When dehydration exceeds 3% of total body water (2% of body mass) then aerobic performance is consistently impaired independent and additive to heat stress. Dehydration augments hyperthermia and plasma volume reductions, which combine to accentuate cardiovascular strain and reduce Vo(2max). Importantly, the negative performance consequences of dehydration worsen as T(sk) increases.
Authors:
Samuel N Cheuvront; Robert W Kenefick; Scott J Montain; Michael N Sawka
Publication Detail:
Type:  Journal Article; Review     Date:  2010-08-05
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  109     ISSN:  1522-1601     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  2010 Dec 
Date Detail:
Created Date:  2010-12-14     Completed Date:  2011-03-25     Revised Date:  2013-09-26    
Medline Journal Info:
Nlm Unique ID:  8502536     Medline TA:  J Appl Physiol (1985)     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1989-95     Citation Subset:  IM    
Affiliation:
US Army Research Institute of Environmental Medicine, Thermal and Mountain Medicine Division, Kansas St., Natick, MA 01760-5007, USA. samuel.n.cheuvront@us.army.mil
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MeSH Terms
Descriptor/Qualifier:
Animals
Body Temperature Regulation
Cardiovascular System / physiopathology
Central Nervous System / physiopathology
Dehydration / physiopathology*
Heat Stress Disorders / physiopathology*
Humans
Muscle Contraction*
Muscle Fatigue
Muscle, Skeletal / innervation,  physiopathology*
Oxygen Consumption
Physical Exertion*
Skin Temperature
Sweating
Water-Electrolyte Balance

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


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