Many people exercise in the water because of its low-impact nature. According to research presented in October at the Canadian Cardiovascular Congress, water exercise may provide similar cardiovascular benefits to land-based workouts.
Twenty-two participants exercised using a dry-land ergocycle and an immersible ergocycle. The dry-land exercise started at 25 watts, increasing by 25 watts each minute until exhaustion. In the water, participants—submerged to chest level—started at about 40 revolutions per minute, increasing by 10 rpm each minute until exhaustion. External power output was measured using equations specific to each environment, taking into account potential drag from pedals, legs, etc.
The researchers found that maximal oxygen consumption was similar for both modalities.
“Exercise during water immersion results in a significantly lower mean VO, O2 pulse and heart rate relative to a land exercise of equivalent power output,” they explained. “These differences are believed to be in part due [to] the hydrostatic forces of water on the body, leading to increased venous return and subsequent rise in cardiac output and compensatory reduction in heart rate, as well as effects on ventilation from external pressure to the chest wall.”
The authors added that further study using a larger sample size was needed to confirm these findings. The abstract of this presentation was published in a supplement of the Canadian Journal of Cardiology (2012; 28, S242).