Exercise studies in horses: 2. The cardiac response to exercise in normal horses and in horses with chronic obstructive pulmonary disease.

The research examines the cardiac response to exercise in healthy horses and in horses with Chronic Obstructive Pulmonary Disease (COPD), focusing on the relationship between velocity and heart rate and between kinetic energy and heart rate.

Methodology

• The researchers studied a total of 12 horses, half of which were healthy and half suffering from COPD.
• They utilized radiotelemetry to identify the heart rate of the horses while they were ridden on a 400-meter track.
• The pace at which the horses were ridden was divided into walk, trot, and gallop.
• The velocity of each horse was determined using a stopwatch between two markers positioned 50 meters apart at the track’s end.
• The kinetic energy was determined using the formula (1/2 Mv2) equating the mass of the horse, rider, saddle, and bridle (measured in kilograms) with velocity (measured in meters per second).

Findings

• It was established that with each individual pace, the correlation between velocity and heart rate was linear in all subjects.
• However, significant differences were noted in the velocity-heart rate (v/HR) regression curves at different paces.
• The data demonstrated that the rise in velocity per unit increase in heart rate was higher at the trot than at the walk, and higher at the gallop than at the trot.
• When all the pace data was combined, the log v/log HR relationship was linear.
• These findings were consistent with the relationship of kinetic energy to the heart rate.

Unique Findings in COPD Horses

• In horses that reached a maximum heart rate at a relatively low velocity, the v/HR curve became asymptotic or reaching a limit.
• Compared to normal horses, the heart rate of the COPD horses was about 20 beats per minute higher at similar submaximal velocities.
• The same pattern was found when “kinetic energy per units mass” was used in place of velocity, indicating COPD horses required notably more cardiac effort than their healthy counterparts at similar exercise intensities.