Pulmonary vascular pressures of thoroughbreds increase rapidly and to a higher level with rapid onset of high-intensity exercise than slow onset.

This study examines how rapid high-intensity exercise affects the pulmonary vascular pressures in Thoroughbred horses, pointing out that these pressures increase faster and to a higher degree compared to slow-onset exercise.

Introduction

• The study addresses a gap in the current understanding of pulmonary vascular pressure dynamics in horses undergoing high-intensity exercise.
• Previous studies had largely focused on gradual onsets of exercise, not considering the fast, high-intensity exercise often experienced in horse racing.

Methodology

• The study involved eight healthy Thoroughbreds performing two different exercise protocols on a high-speed treadmill.
• One protocol involves gradual incremental speed increases, while the other involved rapid acceleration where the belt speed was increased from 8 m/s to 15 m/s within 8 seconds.
• The researchers used catheter-mounted manometers that had been matched with pressure signals via transducers connected to fluid-filled lumens in order to measure the horses’ right heart and pulmonary vascular pressures.

Findings

• The researchers found that the heart rate, right atrial pressure, and pulmonary vascular pressures at rest were similar for both the gradual and rapid onset exercise protocols.
• However, the rapid acceleration of the treadmill speed led to a similarly rapid increase in right heart and pulmonary vascular pressures.
• These pressures reached their highest levels as the treadmill speed approached 15 m/s.
• While the heart rates for both protocols were similar at a speed of 15 m/s, the study noted that the mean atrial pressure, pulmonary artery pressure, pulmonary artery wedge pressure, and pulmonary capillary pressure were all higher with the rapid onset protocol.

Conclusion

• This study suggests that rapid onset, high-intensity exercise causes more severe increases in a horse’s pulmonary vascular pressures compared to slow onset exercise, which could have significant implications for racehorse training and healthcare regimes.