Heart rate response and plasma lactate concentrations of horses competing in the cross-country phase of combined training events.

This study investigates the exercise intensity of 175 horses competing in combined training events’ cross-country phase at various levels. The researchers found that as competition levels increased, the mean plasma lactate also increased significantly, although heart rate differences at different levels were minimal. Rectal temperatures taken 10 minutes after competition were significantly higher than those recorded immediately post-competition.

Detailed Explanation

Study Background and Set-Up

• The study involved examining the exercise intensity of horses participating in the cross-country phase of 4 different combined training events.
• Horses competed at 5 different levels, namely Novice, Training, Preliminary, Intermediate and Advanced. The temperatures varied from a cool and humid environment to moderately hot and humid conditions.
• Heart rates of the horses were recorded continuously at 5-second intervals throughout the cross-country phase, with plasma lactate concentration also checked.

Findings on Heart Rates and Lactate Levels

• The average heart rates for each level of competition found were: Novice: 154.4 bpm, Training: 160.4 bpm, Preliminary: 160.6 bpm, Intermediate: 181 bpm, and Advanced: 194.6 bpm.
• Plasma lactate concentration was gauged at rest for a random selection of horses, and within 60 seconds of completing the cross-country phase for all horses.
• The mean resting lactate concentration was 0.98 mmol/l. After exercise, the lactate concentrations were – Novice: 8.1 mmol/l, Training: 11.5 mmol/l, Preliminary: 17.6 mmol/l, Intermediate: 19 mmol/l, and Advanced: 21.3 mmol/l.
• With an increase in competition levels, the average plasma lactate levels rose significantly, even though significant heart rate differences within the levels were not observed.

Observations on Rectal Temperatures

• Moreover, rectal temperatures of horses were taken immediately after completing the cross-country phase and 10 minutes later.
• The rectal temperatures 10 minutes post completion of the event were seen to be significantly higher than those recorded immediately after the event.
• Rectal temperatures taken 10 minutes after completion of exercise increased significantly as the competition level increased from Novice through Intermediate.
• There was a correlation found between ambient temperatures and rectal temperatures taken 10 minutes after completion of the cross-country phase.
• No significant correlation was found between pulse or respiratory rate taken immediately after completion of exercise with heart rate during the course.