THE MECHANICS OF BREATHING DURING SWIMMING

The thorax undergoes unique conditions while swimming. Hydrostatic pressure from water immersion places an external load on the thorax and increases airway resistance, while the horizontal body position results in central venous engorgement and an associated reduction in lung compliance. The aforementioned factors likely increase the work of breathing (Wb); however, this hypothesis remains untested. Purpose To compare Wb during freestyle swimming relative to cycling, and to characterize the differences in the cardiorespiratory responses to swimming relative to cycling in the same individuals. Methods Eight collegiate swimmers (n=4 male, n=4 female; age= 22±2 y) performed an incremental swim test while tethered to a resistance apparatus. On a separate day subjects performed an incremental cycle test. During swimming and cycling, metabolic and ventilatory parameters were measured using a customized metabolic cart, and inspired Wb was quantified using an esophageal balloon catheter. Results Swimming and cycling elicited statistically similar levels of peak oxygen uptake (3.87±0.92 vs. 4.20±0.83 l·min-1, p=0.143). However, peak minute ventilation (V[Combining Dot Above]E) (118±3 vs. 154±25 l·min-1) and heart rate (164±19 vs. 183±8 beats·min-1) were significantly lower during swimming relative to cycling (both p

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