PURPOSE: To compare physiological responses to a 20-min high intensity, Tabata-style shallow water exercise workout (TS-SWE) between healthy males (M, n=9, 24±1 y) and females (F, n=9, 26±6 y).
METHODS: Participants first performed an incremental SWE test to exhaustion while metabolic (indirect calorimetry), heart rate (HR, telemetry) and blood lactate (Bla) responses were monitored. On a second visit, metabolic, HR, rating of perceived exertion (RPE, Borg scale 6-20), and Bla were measured while participants performed TS-SWE. TS-SWE consisted of 4, 4-min bouts with each bout alternating between 20s “all-out” exercise followed by 10s rest. Each bout was separated by 1 min rest (total of 32 “all-out” 20s efforts). For both visits, participants were immersed to axillary level at a water temp. of 83 F.
RESULTS: M had a greater peak VO2 and Bla (3.6±0.4 vs 2.7±0.3 l.min-1; 10.9±1.3 vs 8.1±1.7 millimolar (mM); p<0.05) while peak HR was similar (185±7 (M) vs 181±7 bpm (F) (p>0.05)). For the overall TS-SWE workout, %V[Combining Dot Above]O2 peak for M and F was 72.9±4.7 and 72.4±6.5, respectively, while %HR peak was 83.9±4.9 (M) and 86.3±2.2 (F), (P>0.05). RPE for the overall workout was ~18-19 (very, very hard) for both M and F. %V[Combining Dot Above]O2 peak for M and F was similar for each bout and increased from ~70% (Bout 1), 74% (Bout 2), to 77% (Bout 3) with the greatest metabolic load achieved during Bout 4 (~85%) (P<0.05, main effect bout). %HR peak was also similar between M and F for each bout: ~82% (Bout 1), 85% (Bout 2), 88% (Bout 3) and ~94% for Bout 4 (P<0.05, main effect bout). Bla (mM) was similar between M and F for bout 1 (6.3±1.8 vs. 5.2±1.6, respectively (p>0.05)), however, males accumulated a greater Bla in bouts 2 (9.0±2.0 vs. 6.0±1.0), 3 (9.3±2.3 vs.5.9±) and 4 (11.1±2.2 vs. 9.2±1.7) (P<0.05).
CONCLUSION: TS-SWE elicited cardiometabolic and psychophysical responses for both males and females that are classified as vigorous to near-maximal to maximal intensity according to the American College of Sports Medicine. Furthermore, the presence of a cardiometabolic “end-spurt”, as reflected in a substantially greater %VO2, %HR peak, and blood lactate response during bout 4, suggests that a pacing strategy may have been employed despite a-priori instructions to exercise “all-out” throughout the workout.