MAXIMAL AND VENTILATORY THRESHOLD RESPONSES TO TREADMILL AND WATER IMMERSION RUNNING

This study compared the metabolic responses of 13 endurance runners, f amiliar with nonweight-bearing water immersion (WI) running, at ventil atory threshold (T-vent) and maximal effort (V over dot O-2max) for bo th treadmill and WI running performance. Oxygen consumption (V over do t O-2), ventilation (V over dot (E)), heart-rare (HR), V over dot (E)/ V over dot O-2, respiratory exchange ratio (RER), perceived exertion ( RPE), and stride frequency (SF) were measured at T-vent and V over dot O-2max. Paired t-tests revealed higher V over dot O-2max (59.7 vs 54. 6 ml . kg .(-1)min(-1)), HR(max) (190 vs 175 bpm), RER(max) (1.20 vs 1 .10), V over dot O-2 at T-vent (46.3 vs 42.8 ml . kg .(-1)min(-1)), HR at T-vent (165 vs 152 bpm) for treadmill versus WI running, respectiv ely. Treadmill and WI V over dot (Emax) (109.0 vs 105.8 1 . min(-1)), RPE(max) (20), V over dot (E) at T-vent (66.4 vs 65.7 1 . min(-1)), RE R at T-vent (0.99 vs 0.98), RPE at T-vent (13 vs 12) were similar, as were blood lactate [BLa] values obtained at 30 s (10.4 vs 9.8 mmol . l (-1)) and 5 min (9.7 vs 9.2 mmol . l(-1)) post-test. SF values over ti me were higher on the treadmill. The lower WI V over dot O-2max with s imilar peak [BLa] and lower SF values suggests that the active muscula ture and muscle recruitment patterns differ in WI running due to the h igh viscosity friction of water, and the nonweight-bearing nature of W I running.