Time limit and (V)over dotO₂ kinetics a maximal aerobic velocity: Continuous vs. intermittent swimming trials

The time sustained during exercise with oxygen uptake ((V) over dotO(2)) reaching maximal rates ((V)over dotO(2peak)) or near peak responses (i.e., above second ventilatory threshold [t@VT2) or 90% (V)over dotO(2peak) (t@90%(V)over dotO(2peak))] is recognized as the training pace required to enhance aerobic power and exercise tolerance in the severe domain (time-limit, t(Lim)). This study compared physiological and performance indexes during continuous and intermittent trials at maximal aerobic velocity (MAV) to analyze each exercise schedule, supporting their roles in conditioning planning. Twenty-two well-trained swimmers completed a discontinuous incremental step-test for (V)over dotO(2peak), VT2, and MAV assessments. Two other tests were performed in randomized order, to compare continuous (CT) vs. intermittent trials (IT100) at MAV until exhaustion, to determine peak oxygen uptake (Peak-(V)over dotO(2)) and (V)over dotO(2) kinetics ((V) over dotO(2)K). Distance and time variables were registered to determine the t(Lim), t@VT2, and t@90%(V)over dotO(2peak )tests. Blood lactate concentration ([La-]) was analyzed, and rate of perceived exertion (RPE) was recorded. The tests were conducted using a breath-by-breath apparatus connected to a snorkel for pulmonary gas sampling, with pacing controlled by an underwater visual pacer. (V)over dotO(2peak) (55.2 +/- 5.6 ml.kg.min(-1)) was only reached in CT (100.7 +/- 3.1 % (V)over dotO(2peak)). In addition, high (V)over dotO(2) values were reached at IT100 (96.4 +/- 4.2 % (V)over dotO(2peak)). (V)over dotO(2peak) was highly correlated with Peak-(V)over dotO(2)during CT (r = 0.95, p < 0.01) and IT100 (r = 0.91, p < 0.01). Compared with CT, the IT100 presented significantly higher values for t(Lim) (1,013.6 +/- 496.6 vs. 256.2 +/- 60.3 s), distance (1,277.3 +/- 638.1 vs. 315.9 +/- 63.3 m), t@VT2 (448.1 +/- 211.1 vs. 144.1 +/- 78.8 s), and t@90%(V) over dotO(2peak) (321.9 +/- 208.7 vs. 127.5 +/- 77.1 s). (V) over dotO(2)K time constants (IT100: 25.9 +/- 9.4 vs. CT: 26.5 +/- 7.5 s) were correlated between tests (r = 0.76, p < 0.01). Between CT and IT100, t(Lim) were not related, and RPE (8.9 +/- 0.9 vs. 9.4 +/- 0.8) and [La-] (7.8 +/- 2.7 vs. 7.8 +/- 2.8 mmol.l(-1)) did not differ between tests. MAV is suitable for planning swimming intensities requiring (V)over dotO(2)peak rates, whatever the exercise schedule (continuous or intermittent). Therefore, the results suggest IT100 as a preferable training schedule rather than the CT for aerobic capacity training since IT100 presented a significantly higher t(Lim), t@VT2, and t@90%(V)over dotO(2peak )(similar to 757, similar to 304, and similar to 194 s more, respectively), without differing regards to [La-] and RPE. The (V)over dotO(2)K seemed not to influence t(Lim) and times spent near (V)over dotO(2peak )in both workout modes.