Cardiorespiratory responses during underwater and land treadmill exercise in college athletes

Underwater treadmill (UTM) exercise is being used with increased frequency for rehabilitation of injured athletes, yet there has been little research conducted on this modality.

To determine the cardiorespiratory responses of UTM vs land treadmill (LTM) exercise, particularly with respect to the relationship between heart rate (HR) and oxygen consumption (VO2).

This quantitative original research took place in sports medicine and athletic training facilities at Wake Forest University.

11 Wake Forest University student athletes (20.8 ± 0.6 y, 6 women and 5 men).

All participants completed the UTM and LTM exercise-testing protocols in random order. After 5 min of standing rest, both UTM and LTM protocols had 4 stages of increasing belt speed (2.3, 4.9, 7.3, and 9.6 km/h) followed by 3 exercise stages at 9.6 km/h with increasing water-jet resistance (30%, 40%, and 50% of jet capacity) or inclines (1%, 2%, and 4% grade).

A Cosmed K4b2 device with Polar monitor was used to collect HR, ventilation (Ve), tidal volume (TV), breathing frequency (Bf), and VO2 every minute. Ratings of perceived exertion (RPE) were also obtained each minute.

There was no significant difference between UTM and LTM for VO2 at rest or during any stage of exercise except stage 3. Furthermore, there were no significant differences between UTM and LTM for HR, Ve, Bf, and RPE on any exercise stage. Linear regression of HR vs VO2, across all stages of exercise, indicates a similar relationship in these variables during UTM (r = .94, y = .269x - 10.86) and LTM (r = .95, y = .291x - 12.98).

These data indicate that UTM and LTM exercise elicits similar cardiorespiratory responses and that HR can be used to guide appropriate exercise intensity for college athletes during UTM.