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  • Author or Editor: Hajime Ohmura x
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Abstract

OBJECTIVE To determine cardiorespiratory responses of Thoroughbreds to uphill and downhill locomotion on a treadmill at identical gradients.

ANIMALS 5 highly trained Thoroughbred geldings.

PROCEDURES Thoroughbreds were exercised for 2-minute intervals on a treadmill at 1.7, 3.5, 6.0, 8.0, and 10.0 m/s at a 4% incline, 0% incline (horizontal plane), and 4% decline in random order on different days. Stride frequency, stride length, and cardiopulmonary and O2-transport variables were measured and analyzed by means of repeated-measures ANOVA and Holm-Šidák pairwise comparisons.

RESULTS Horses completed all treadmill exercises with identical stride frequency and stride length. At identical uphill speeds, they had higher (vs horizontal) mass-specific O2 consumption (mean increase, 49%) and CO2 production (mean increase, 47%), cardiac output (mean increase, 21%), heart rate (mean increase, 11%), and Paco2 (mean increase, 1.7 mm Hg), and lower Pao2 (mean decrease, 5.8 mm Hg) and arterial O2 saturation (mean decrease, 1.0%); tidal volume was not higher. Downhill locomotion (vs horizontal) reduced mass-specific O2 consumption (mean decrease, 24%), CO2 production (mean decrease, 23%), and cardiac output (mean decrease, 9%). Absolute energy cost during uphill locomotion increased linearly with speed at approximately twice the rate at which it decreased during downhill locomotion.

CONCLUSIONS AND CLINICAL RELEVANCE Findings suggested that for Thoroughbreds, downhill locomotion resulted in a lower energy cost than did horizontal or uphill locomotion and that this cost changed with speed. Whether eccentric training induces skeletal muscle changes in horses similar to those in humans remains to be determined.

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE To determine whether racehorses undergoing regular exercise at 2 intensities or stall rest during a period of reduced training (detraining) would differentially maintain their cardiopulmonary and oxygen-transport capacities.

ANIMALS 27 Thoroughbreds.

PROCEDURES Horses trained on a treadmill for 18 weeks underwent a period of detraining for 12 weeks according to 1 of 3 protocols: cantering at 70% of maximal rate of oxygen consumption (o2max) for 3 min/d for 5 d/wk (canter group); walking for 1 h/d for 5 d/wk (walk group); or stall rest (stall group). Standardized treadmill exercise protocols (during which cardiopulmonary and oxygen-transport variables were measured) were performed before and after detraining.

RESULTS Mass-specific o2max, maximal cardiac output, and maximal cardiac stroke volume of all groups decreased after 12 weeks of detraining with no differences among groups. After detraining, arterial-mixed-venous oxygen concentration difference did not decrease in any group, and maximal heart rate decreased in the walk and stall groups. Run time to exhaustion and speeds eliciting o2max and maximal heart rate and at which plasma lactate concentration reached 4mM did not change in the canter group but decreased in the walk and stall groups.

CONCLUSIONS AND CLINICAL RELEVANCE Horses following the cantering detraining protocol maintained higher values of several performance variables compared with horses following the walking or stall rest protocols. These results suggested that it may be possible to identify a minimal threshold exercise intensity or protocol during detraining that would promote maintenance of important performance-related variables and minimize reductions in oxygen-transport capacity in horses.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate the effects of dorsal versus lateral recumbency on the cardiopulmonary system during isoflurane anesthesia in red-tailed hawks (Buteo jamaicensis).

Animals—6 adult 1.1- to 1.6-kg red-tailed hawks.

Procedures—A randomized, crossover study was used to evaluate changes in respiratory rate, tidal volume, minute ventilation, heart rate, mean arterial and indirect blood pressures, and end-tidal Pco 2 measured every 5 minutes plus Paco 2 and Pao 2 and arterial pH measured every 15 minutes throughout a 75-minute study period.

Results—Respiratory rate was higher, tidal volume lower, and minute ventilation not different in lateral versus dorsal recumbency. Position did not affect heart rate, mean arterial blood pressure, or indirect blood pressure, although heart rate decreased during the anesthetic period. Birds hypoventilated in both positions and Paco 2 differed with time and position × time interaction. The Petco 2 position × time interaction was significant and Petco 2 was a mean of 7 Torr higher than Paco 2. The Paco 2 in dorsal recumbency was a mean of 32 Torr higher than in lateral recumbency. Birds in both positions developed respiratory acidosis.

Conclusions and Clinical Relevance—Differences in tidal volume with similar minute ventilation suggested red-tailed hawks in dorsal recumbency might have lower dead space ventilation. Despite similar minute ventilation in both positions, birds in dorsal recumbency hypoventilated more yet maintained higher Pao 2, suggesting parabronchial ventilatory or pulmonary blood flow distribution changes with position. The results refute the hypothesis that dorsal recumbency compromises ventilation and O2 transport more than lateral recumbency in red-tailed hawks.

Full access
in American Journal of Veterinary Research