Abstract
Introduction. Water immersion is known to add additional drag and metabolic demand for limb movement with respect to air. We tested the hypothesis that this effect would translate into an increased internal metabolic power (Ėint) during cycling.
Methods. 12 healthy subjects (4 females) pedalled on a waterproof cycle ergometer in an experimental pool that was either empty (DRY) or filled with tap water at 30.8 ± 0.6 °C (WET). Four different pedal cadences (fp) were studied (40, 50, 60 and 70 rpm) at four different workloads. The metabolic power at steady state was measured via open circuit respirometry and Ėint was calculate as the metabolic power extrapolated for 0 W.
Results. Ėint was higher in WET in for all investigated p except 40 rpm. Ėint increased with the third power of fp both in WET and DRY.
Conclusions. Cycling in the water increases Ėint, however, limb unloading via the Archimedes’ principle could potentially be a confounding factor. A simple formula was developed to predict the increase in mechanical power in dry conditions needed to match energy expenditure of underwater cycling: 44*fp3 – 7 W, where fp is expressed in Hz.