Prescribing water-based exercise from treadmill and arm ergometry in cardiac patients

This study investigated the appropriateness of prescribing upright water-based exercise from treadmill and arm ergometry in uncomplicated, trained patients with cardiovascular disease (CVD) who were accustomed to water-based activities. Ten male patients with established CVD (mean age 59.4 ± 8.7 yr) underwent maximal treadmill and arm ergometry in randomized counterbalanced order (half of the patients completed the treadmill test first and the other half completed the arm ergometer test first). Electrocardiographic (ECG), rating of perceived exertion (RPE), and oxygen uptake (VO₂) measurements were made during both tests. Patients performed upright water-based exercise at 60, 70, and 80% of their maximal treadmill heart rate for 6 min at each intensity in a heated pool with a water temperature of 28-30°C. They also performed an easy tethered swim, defined as performing at a comfortable exercise intensity, eliciting a heart rate of 86% of the treadmill maximum. VO₂ and RPE were collected for all water-based exercise. To compare the RPE and VO₂ between water-based, treadmill, and arm ergometry exercise, individual regression equations were constructed between heart rate, VO₂, and RPE for both treadmill and arm ergometry tests. VO₂ and RPE were then compared at the same heart rates between the three exercise modes. At 60% intensity, treadmill exercise exhibited a higher VO₂ than water-based and arm ergometry exercise (P< 0.05) but similar RPE. At 70%, treadmill exercise still yielded higher VO₂, but also lower RPE than (P< 0.05) and arm ergometry exercise (P< 0.05). At 80%, treadmill VO₂ was greater than both arm ergometer and water-based VO₂ (P < 0.05). These data show that low intensity water-based exercise elicits similar metabolic demands and RPE to arm ergometry at the same heart rates. However, high intensity water-based exercise (80% of the treadmill HR_max) elicited a higher VO₂ but a lower RPE than arm ergometry. Treadmill exercise consistently elicited greater VO₂ than water-based exercise at the same heart rates and similar or lower RPEs.