Circulatory and muscle metabolic responses to draught work compared to increasing trotting velocities.

This study explores the effect of two types of exercises – incremental draft work and exercises with increasing speed – on the muscular and circulatory responses of 10 horses. The study found that muscle metabolites and heart rate responses differ between the two exercise types, with high oxidative capacity being important for both fast trotting and draft work.

Study Methodology

• The research involved ten horses which performed two different types of exercises: incremental draught work at low trotting speed on a treadmill (referred to as the D-test), and an exercise regime with incrementally increasing velocities (the S-test).
• The exercises were stopped when the horses could no longer maintain the weights above the floor or maintain trotting speed without switching to a gallop.
• Muscle biopsies were drawn from the gluteus and the semitendinosus muscles both before and immediately after the exercises.

Research Findings

• The heart rate (HR) response in the animals increased linearly with both increasing draught resistance and velocity, reaching average values of 212 beats/min and 203 beats/min, respectively.
• Blood lactate levels grew exponentially, reaching an average of 12.9 mmol/litre and 7.9 mmol/litre in the D-test and S-test respectively.
• Both heart rate and blood lactate levels were significantly higher at the end of the D-test compared to the S-test.
• The relationship between heart rate and blood lactate response in the S-test was found to be similar to that in the D-test.
• Red cell volume, determined after a standardised exercise tolerance test, was significantly correlated both to weight lifting and the velocity that got the horses to a heart rate of 200 beats/min.
• Changes in muscle glycogen and glucose-6-phosphate were similar in both tests. However, the D-test led to significantly higher lactate levels and lower creatine phosphate and adenosine triphosphate levels than the S-test.

Conclusion

• The study concluded that a high oxidative capacity is crucial for both fast trotting and draught work in horses. This implies, for instance, that training regimes for these animals should take their oxidative capacities into account.