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Cardiopulmonary Function in Thoroughbred Horses Running Uphill and Downhill on an Inclined Treadmill
Author(s) -
Ohmura H,
Mukai K,
Takahashi T,
Aida H,
Jones J
Publication year - 2014
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/evj.12267_75
Subject(s) - treadmill , eccentric , stride , cardiology , heart rate , concentric , horse , running economy , medicine , vo2 max , zoology , mathematics , anesthesia , physical medicine and rehabilitation , physics , biology , geometry , blood pressure , paleontology , quantum mechanics
Eccentric muscle contractions (“negative” work, e.g., downhill running) affect human skeletal muscle differently than concentric contractions, increasing muscle size and strength more than concentric exercise training with reduced oxygen consumption ( VO 2 ). Better understanding of skeletal muscle and cardiopulmonary responses to downhill training may indicate a role for this in Thoroughbred training. We hypothesised that Thoroughbreds would reduce metabolic energy cost and cardiopulmonary function when they ran at equivalent speed on a declined treadmill compared with running horizontally or uphill. Methods Five well‐trained Thoroughbreds ran for 2‐min incremental exercise intervals on a treadmill at 1.7, 3.5, 6.0, 8.0 and 10.0 m/s on a +4% incline, 0% incline (horizontal) and −4% decline in random order on different days. Cardiopulmonary and O 2 ‐transport variables were measured and analysed with two‐way repeated‐measures ANOVA and Holm‐Šidák pairwise‐comparisons. Results Horses ran at all inclines with identical stride frequency and length. At identical uphill speeds they had significantly higher (vs. horizontal) mass‐specific VO 2 (43% mean increase) and CO 2 production ( VCO 2 / Mb ), cardiac output ( Q / Mb ), heart rate, arterial CO 2 tension ( PaCO 2 ), and reduced arterial O 2 tension and saturation; tidal volume tended to be higher (P = 0.060). Downhill running reduced (vs. horizontal) VO 2 / Mb (19% mean decrease), VCO 2 / Mb , Q / Mb and PaCO 2 . Fractional energy cost increase (incline) and reduction (decline) decreased linearly with increasing speed. Conclusions Thoroughbreds run downhill with lower energy cost than on the level or uphill and the cost changes with speed. It remains to be determined if eccentric training induces skeletal muscle changes in horses. Ethical Animal Research The study was approved by the Animal Welfare and Ethics Committee of the Equine Research Institute, J apan Racing Association. Sources of funding: none. Competing interests: none.