Cardiorespiratory adjustments to tethered-swimming in the horse.

This research study examines how tethered swimming impacts the cardiorespiratory and metabolic responses of five sedentary horses. The researchers found a high correlation between heart rate and work effort, with a significant increase in various pressure levels in circulatory systems during exercise. The findings also indicate that horses have a higher aerobic capacity than humans and their increase in oxygen uptake during exercise can’t be solely attributed to increased cardiac output.

Research Context and Procedure

• This study was conducted on five sedentary horses, i.e, horses with minimal physical activity in their routine.
• The purpose of the research was to evaluate and measure cardiorespiratory and metabolic responses during varying levels of tethered swimming — a form of exercise where the horse swims in place secured by a tether.
• Standard physical parameters like cardiac output, heart rate, stroke volume, pulmonic and systemic pressure, lactic acid levels, and oxygen uptake were closely monitored and measured.
• The work effort was defined and measured as the weight pulled by the horse proportional to its body weight.

Research Findings

• The results demonstrated a strong correlation between cardiac output, heart rate and the work effort.
• Notably, the stroke volume was found to decrease at low workloads, increase with workload, and return to normal standing levels at the peak workload.
• Swimming not only considerably increased the pressures across the horse’s circulatory system, but the mean carotid artery pressure was also found to be strongly related to work effort.
• The blood lactic acid levels were found to increase exponentially with rising heart rates.
• Oxygen uptake also showed a linear increase alongside the increase in work effort, suggesting a potentially higher aerobic capacity in horses compared to humans.

Implications

• The study concluded that the increase in oxygen uptake observed in horses during exercise is not just due to increased cardiac output. Other factors such as changes in hematocrit (the ratio of the volume of red cells to the volume of whole blood), hemoglobin, and oxygen extraction are also seen to play a significant role.
• This indicates that horses’ physiology adapts to exercise more efficiently than humans because their aerobic capacity appears to be twice that of humans.
• This research provides significant insights for equine training and <a href="/equine-rehabilitation-guide/" title="rehabilitation programs, as well as for understanding the comparative physiology between different species.