Document Detail

Cardiorespiratory and metabolic responses to treadmill exercise in the horse.
MedLine Citation:
PMID:  7263369     Owner:  NLM     Status:  MEDLINE    
The purpose of this study was to measure cardiovascular, respiratory, and metabolic responses to graded treadmill exercise in the horse. A five-stage treadmill test up to 90% of predicted maximal heart rate was administered to five sedentary horses. The highest measured level of exercise produced a sixfold increase in cardiac output and a 41% elevation of stroke volume over standing values. Left ventricular, arterial, and right atrial pressures as well as the maximal time derivative of left ventricular pressure were all elevated during exercise. Under the same two conditions hematocrit (Hct) increased from 33 +/- 2 to 47 +/- 1%, oxygen uptake (VO2) from 1.1 +/- 0.1 to 32.7 +/0 2.1 1.min-1, and respiratory exchange ratio (RQ) increased from 0.83 +/- 0.02 to 0.96 +/- 0.01. In addition, three of the horses were willing to trot at a sixth stage (14 km.h-1, 11.5% grade), which elicited a VO2 of 39.8 +/- 0.31.min-1 and an RQ of 0.98 +/- 0.01. In response to the sympathetic stimulation of exercise, the horse is able to elevate Hct, hemoglobin, and oxygen-carrying capacity by emptying the spleen, thus increasing total circulating red blood cells by as much as 50%. This enabled three of the five horses used in the present study to increase aerobic metabolism almost 40-fold above resting or twice that seen in humans. Therefore, in the horse "blood-boosting" is an efficient mechanism for increasing aerobic metabolism. This finding lends further support to the view that the oxygen transport system limits maximal aerobic capacity in humans.
D P Thomas; G F Fregin
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of applied physiology: respiratory, environmental and exercise physiology     Volume:  50     ISSN:  0161-7567     ISO Abbreviation:  J Appl Physiol Respir Environ Exerc Physiol     Publication Date:  1981 Apr 
Date Detail:
Created Date:  1981-10-25     Completed Date:  1981-10-25     Revised Date:  2013-09-26    
Medline Journal Info:
Nlm Unique ID:  7801242     Medline TA:  J Appl Physiol Respir Environ Exerc Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  864-8     Citation Subset:  IM; S    
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MeSH Terms
Blood Pressure
Cardiac Output
Cardiovascular Physiological Phenomena*
Exercise Test / veterinary*
Heart / physiology
Heart Rate
Horses / physiology*
Models, Biological
Oxygen Consumption

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

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