VO2 Kinetics during Different Forms of Cycling Exercise on Land and in Water

Background: It is generally assumed that the physical properties of water improve aerobic me- tabolism by O 2 utilization of the working muscle particular if a great muscle mass is recruited. This study investigated the changes in VO 2 (VO 2 -work rate relationship; ∆ VO 2 / ∆ WR) during increasing work rates in different exercise conditions in water immersed exercise and on land based exercise. Methods: In order to identify possible differences in VO 2 required for a given work rate twelve trained cyclists performed four incremental exercise tests. The tests comprised whole body work and leg work, both in water and on land and were conducted on the same, electromagneti- cally braked whole body ergometer. Results: The ∆ VO 2 / ∆ WR curves were found to be similar in the four exercise conditions reach- ing from 11.9 to 12.4 ml·W -1 during water immersed exercise and 12.6 to 12.7 ml·W -1 dur- ing land based exercise respectively. When coupling arms with leg exercise the ∆ VO 2 / ∆ WR curves shift upwards at similar work rates indicating a higher oxygen demand for an enlarged muscle mass. The extra O 2 cost ( ∆ VO 2 ) for recruited arms was lower in water immersed exercise compared to land based exercise (0.057±0.072 l ·min -1 and 0.367 1±0.057·min -1 , respectively; p=.000). Differences exist in the rate of performing physical work above ventilatory threshold two. Work load values attained on land based exercise surpass that of water immersed exercise (204.2 watts vs. 154.0 watts for whole body work and 227.1 watts vs. 150.0 watts for leg work, respectively). Conclusions: Differences in ∆ VO 2 at a given work rate are to be explained rather from a biome- chanical point of view. More likely ∆ VO 2 in water seems to be influenced by both familiarity of the task and fitness level. Exercise intensity in water need to be selected at lower levels than on land.