Cardio-respiratory and plasma lactate responses to exercise with low draught resistances in standardbred trotters.

The research studies the effect of low draught resistances on heart rate, respiratory rate, and plasma lactate levels during exercise in five Standardbred trotters. The study concludes that increasing the draught resistance from 10 to 30 kilopond significantly elevates the horses’ heart rate and plasma lactate responses, although individual differences in physiological reaction to exercise exist among the horses.

Methodology

• The study involved five Standardbred trotters. These horses were made to perform treadmill exercise at progressively higher trotting speeds for two-minute intervals. This activity was conducted in three separate tests with the variables being the draught loads of 10, 20, or 30 kilopond (kp).
• Each trotting interval was succeeded by a two-minute walking period without any draught load. Measurements of heart rate (HR), respiratory rate (RR), plasma lactate (PLA), and stride frequency (SF) were taken after each trotting session.
• Peak oxygen uptake (VO2peak) was calculated in an independent test on an inclined treadmill with increasing speeds and no draught load. Muscle biopsies were also taken from the gluteus muscle of the horses to identify any individual variations.

Findings

• Heart rate increased with higher draught loads, with average rates of 191 +/- 10, 203 +/- 10, and 214 +/- 7 bpm during the three tests. The Plasma lactate levels also increased, reaching 3.8 +/- 0.7, 7.3 +/- 3.8, and 10.8 +/- 6.4 mmol/l at 9 m/s in the three tests. Both heart rate and plasma lactate levels were found significantly higher with 30 kp compared to 10 kp draught resistance.
• The test with a draught load of 30 kp revealed the lowest respiratory rate among the horses.
• The horses reflected individual differences in physiological responses to exercise, including VO2peak, muscle fibre composition, and heart rate and plasma lactate responses.

Conclusion

• At a particular velocity, a minor increase in draught resistance from 10 to 30 kp significantly increases both the heart rate and plasma lactate responses in horses.
• Despite the increase in work intensities being comparable, the horses showed varying circulatory and metabolic responses to the exercise.