Some metabolic effects of maximal exercise in the horse and adaptations with training

The effects of intermittent maximal exercise (galloping) before and after a 10 week training programme were studied in 6 horses. Determinations were carried out on venous blood for packed cell volume, total plasma protein, glucose, glycerol, free fatty acids, lactate, 11-hydroxycorticosteroids, blood gases and pH. There were marked changes associated with galloping and some of these could be modified with training. The major findings included (i) an elevated blood glucose, (ii) a large increase in glycerol, which was greatest at 30 min post-exercise and was higher following training, (iii) smaller increases in free fatty acids following training, (iv) higher levels of lactate after training, (v) a marked fall in pH which was less after training, (vi) an increase in 11-hydroxycorticosteroids with possibly a more rapid return to resting levels following training. It was concluded that with maximal exercise in the horse both glycogen and free fatty acids served as important substrates for working muscle, and following training greater utilisation of both these substrates occurred.