Respiratory Response to Underwater and Land‐based Cycling at the Matched Oxygen Uptake

Abstract

Water immersion increases breathing effort against elevated hydrostatic pressure. Thus, aquatic exercise training may have a greater benefit for the respiratory function when compared to the same intensity of exercise performed on dryland. The purpose of this study was to investigate the effect of underwater cycling on the respiratory function and breathing pattern when compared to land-based cycling performed at the matched exercise intensity. Ten healthy men performed maximal graded exercise test and 15 minutes of incremental water-based cycling exercise (WE) and land-based cycling exercise (LE) on separate days. In WE, cycling began at 30 rpm, and the cadence was increased by 15 rpm every 5 minutes. 3 paddles were attached to the wheel of stationary bicycle to increase pedaling resistance. In LE, participants cycled continuously at 60 rpm for 15 minutes while wattage was adjusted to match oxygen uptake (VO2) to the WE condition. Using spirometry, respiratory function and respiratory muscle pressure were measured before and after cycling, and the magnitude of change between pre- and post- exercise was also measured. Breathing pattern was measured continuously during cycling. Water temperature and immersion level were kept at 31.5 ℃ and xiphoid appendix, respectively. VO2 duringcycling in water and on dryland was similar. Minute ventilation, inspiratory and expiratory volumes, and respiratory rate increased whereas, inspiratory and expiratory times decreased as the cycling intensity (VO2) increased (all P < 0.05). Respiratory rate was slightly higher at 60 rpm in WE than LE (27 ± 3 vs. 24 ± 3 bpm, P = 0.053). Inspiratory time was significantly higher at rest in WE than LE (1.4 ± 0.1 vs. 1.2 ± 0.0 sec, P < 0.05). After cycling exercise, change in the forced expiratory volume in one second and change in the peak expiratory flow were significantly lower in WE than LE (-0.04 ± 0.15 vs. 0.06 ± 0.10 L, P < 0.05. -0.37 ± 0.87 vs. 0.04 ± 0.63 L, P < 0.05, respectively). These data suggest that the respiratory and breathing responses were mostly similar during underwater and land-based cycling when VO2 is matched in both conditions. However, breathing may slightly be shallower during a higher-intensity aquatic cycling which may have chronic effects on respiratory function after multiple bouts of aquatic cycling for a longer term.