The intensity of exercise in deep-water running.

The intensity of exercise during 30-min sessions of continuous deep-water running at a "hard" pace was determined by monitoring oxygen consumption (VO2), respiratory quotient (RQ), heart rate, perceived physical effort and perceived aches and pains in the legs in eight competitive runners, six of whom had not previously practised the technique. The intensity was compared with that of 30-min runs on a treadmill at hard and "normal" training paces and a 30-min outdoor run at normal training pace. VO2 during the last session of deep-water running (73% of maximum VO2) was not significantly different from that of the treadmill hard run (78%), but was significantly higher than that of the treadmill normal run (62%). Similar results were obtained for RQ, perceived effort and pain. In contrast, heart rates for deep-water running were similar to those of normal training and significantly less than those of the treadmill hard run. The disparity between VO2 and heart rate for deep-water running may reflect cooling or increased venous return caused by water immersion. It is concluded that deep-water running can be performed at a sufficient intensity for a sufficient period to make it an effective endurance training technique.