title: Changes in maximum oxygen uptake during prolonged training, overtraining, and detraining in horses.
abstract: Thirteen standardbred horses were trained as follows: phase 1 (endurance training, 7 wk), phase 2 (high-intensity training, 9 wk), phase 3 (overload training, 18 wk), and phase 4 (detraining, 12 wk). In phase 3, the horses were divided into two groups: overload training (OLT) and control (C). The OLT group exercised at greater intensities, frequencies, and durations than group C. Overtraining occurred after 31 wk of training and was defined as a significant decrease in treadmill run time in response to a standardized exercise test. In the OLT group, there was a significant decrease in body weight (P < 0.05). From pretraining values of 117 +/- 2 (SE) ml.kg-1.min-1, maximal O2 uptake (VO2max) increased by 15% at the end of phase 1, and when signs of overtraining were first seen in the OLT group, VO2max was 29% higher (151 +/- 2 ml.kg-1.min-1 in both C and OLT groups) than pretraining values. There was no significant reduction in VO2max until after 6 wk detraining when VO2max was 137 +/- 2 ml.kg-1.min-1. By 12 wk detraining, mean VO2max was 134 +/- 2 ml.kg-1.min-1, still 15% above pretraining values. When overtraining developed, VO2max was not different between C and OLT groups, but maximal values for CO2 production (147 vs. 159 ml.kg-1.min-1) and respiratory exchange ratio (1.04 vs. 1.11) were lower in the OLT group. Overtraining was not associated with a decrease in VO2max and, after prolonged training, decreases in VO2max occurred slowly during detraining.
authors.affiliation: Department of Animal Health, University of Sydney, New South Wales, Australia.
authors.forename: C M
authors.initials: CM
authors.lastname: Tyler
authors.forename: L C
authors.initials: LC
authors.lastname: Golland
authors.forename: D L
authors.initials: DL
authors.lastname: Evans
authors.forename: D R
authors.initials: DR
authors.lastname: Hodgson
authors.forename: R J
authors.initials: RJ
authors.lastname: Rose
mesh_terms: D000818:Animals; D001835:Body Weight / Q000502:physiology; D005080:Exercise Test; D006736:Horses; D007700:Kinetics; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology*; D010805:Physical Conditioning, Animal; D010807:Physical Endurance / Q000502:physiology; D012129:Respiratory Function Tests; D013997:Time Factors