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Retrospective study of predictive variables for maximal heart rate (HR max ) in horses undergoing strenuous treadmill exercise
Author(s) -
VINCENT T. L.,
NEWTON J. R.,
DEATON C. M.,
FRANKLIN S. H.,
BIDDICK T.,
McKEEVER K. H.,
McDONOUGH P.,
YOUNG L. E.,
HODGSON D. R.,
MARLIN D. J.
Publication year - 2006
Publication title -
equine veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.82
H-Index - 87
eISSN - 2042-3306
pISSN - 0425-1644
DOI - 10.1111/j.2042-3306.2006.tb05531.x
Subject(s) - horse , heart rate , treadmill , linear regression , medicine , breed , regression analysis , analysis of variance , physical therapy , cardiology , zoology , mathematics , statistics , blood pressure , biology , paleontology
Summary Reasons for performing study: Heart rate is one of the most commonly measured variables in equine exercise physiology and relative exercise intensity commonly expressed as % of maximal heart rate. A number of influences affect maximal heart rate (HR max ), including age of the horse but other factors have not been described. Objectives: To determine if fitness, health status, gender, breed, athletic use, body mass, in addition to age, are predictive of HR max in the horse. Methods: Maximal heart rate data from 328 horses which underwent treadmill exercise tests at 5 different laboratories were obtained retrospectively. Univariable linear regression analyses were performed on individual variables. Multiple linear regression analysis using a backward elimination modelling procedure was then used to relate the observed HR max values simultaneously with different predictive variables. Variables were retained in the final regression model if they or any of their categories were significantly predictive of HR max at P<0.05 and if there was a significant collective contribution to the model from inclusion of each variable, also at P<0.05. Results: Age, fitness status, laboratory, gender and breed/use (combined category) were all statistically significantly predictive of HR max . Together these variables accounted for 41% of the variance in HR max . Age alone accounted for only ˜13% of the variation between horses in HR max . Neither body mass nor health status were significantly predictive. Conclusions: HR max in the horse declines with age but is also influenced by other factors. As the factors investigated accounted for only 41% of the variation between horses, other unidentified variables with a strong influence on HR max remain to be identified. Potential relevance: Factors such as fitness, age, gender, breed and use need to be considered when interpreting estimates or measurements of HR max .