Comparison of exercise variables measured during intensity of simulated training to variables at maximal effort in...

The heart rate changes during routine training in a group of 8 actively racing Standardbreds were used to simulate the training work on a treadmill (ST) and indices of exercise compared to maximal effort (MAX) on the treadmill. The following parameters were recorded during treadmill work: heart rate, velocity, O2 consumption, respiratory and stride frequency, and stride length. Blood lactate concentrations were measured before and after each work test. Heart rate during simulated training was mean +/- s.d. 87.8 +/- 5.5% heart rate in MAX, one of the 8 horses working < 80% of maximal HR and 2 of the 8 horses working above 90% maximal heart rate. Mean +/- s.d. oxygen consumption during the ST was 75.1% +/- 8.4% MAX, but correlated poorly against percentage heart rate for individual horses (r2 = 0.02). At similar velocities for the ST and MAX, only respiratory frequency differed significantly (P > 0.05), being higher during the ST. Most horses worked at intensities based on heart rate consistent with proposed guidelines of 80-90% of maximal heart rate. However, in 3 of the 8 horses work intensity of insufficient or excessive amounts may have occurred.