CARDIORESPIRATORY RESPONSES TO UNDERWATER TREADMILL WALKING IN HEALTHY FEMALES

This study compared the cardiorespiratory responses of eight healthy w omen (mean age 30.25 years) to submaximal exercise on land (LTm) and w ater treadmills (WTm) in chest-deep water (Aquaciser). In addition, th e effects of two different water temperatures were examined (28 and 36 degrees C). Each exercise test consisted of three consecutive 5-min b outs at 3.5, 4.5 and 5.5 km.h(-1). Oxygen consumption ((V) over dot O- 2) and heart rate (HR), measured using open-circuit spirometry and tel emetry, respectively, increased linearly with increasing speed both in water and on land. At 3.5 km.h(-1) (V) over dot O-2 was similar acros s procedures [chi = 0.6 (0.05) l.min(-1)]. At 4.5 and 5.5 km.h(-1) (V) over dot O-2 was significantly higher in water than on land, but ther e was no temperature effect (WTm: 0.9 and 1.4, respectively; LTm: 0.8 and 0.9 l.min(-1), respectively). HR was significantly higher in WTm a t 36 degrees C compared to WTm at 28 degrees C at all speeds, and comp ared to LTm at 4.5 and 5.5 km.h(-1) (P less than or equal to 0.003). T he HR-(V) over dot O-2 relationship showed that at a (V) over dot O-2 of 0.9 l.min(-1), HR was higher in water at 36 degrees C (115 beats.mi n(-1)) than either on land (100 beats.min(-1)) or in water at 28 degre es C (99 beats.min(-1)). The Borg scale of perceived exertion showed t hat walking in water at 4.5 and 5.5 km.h(-1) was significantly harder than on land (WTm: 11.4 and 14, respectively; LTm: 9.9 and 11, respect ively; P less than or equal to 0.001). These cardiorespiratory changes occurred despite a slower cadence in water (the mean difference at al l speeds was 27 steps/min). Thus, walking in chest-deep water yields h igher energy costs than walking at similar speeds on land. This data h as implications for therapists working in hydrotherapy pools.