AUTHOR=Almeida Tiago A. F. , Massini Danilo A. , Silva Júnior Osvaldo T. , Venditti Júnior Rubens , Espada Mário A. C. , Macedo Anderson G. , Reis Joana F. , Alves Francisco B. , Pessôa Filho Dalton M. 

TITLE=Time limit and V̇O2 kinetics at maximal aerobic velocity: Continuous vs. intermittent swimming trials

JOURNAL=Frontiers in Physiology

VOLUME=Volume 13 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2022.982874

DOI=10.3389/fphys.2022.982874

ISSN=1664-042X

ABSTRACT=The time sustained during exercise with oxygen uptake (V̇O2) reaching maximal rates (V̇O2peak) or near peak responses (i.e., above second ventilatory threshold (t@VT2) or 90% V̇O2peak (t@90%V̇O2peak)) is recognized as the training pace required to enhance aerobic power and exercise tolerance in the severe domain (time-limit, tLim). 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 V̇O2peak, 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-V̇O2) and V̇O2 kinetics (V̇O2K). Distance and time variables were registered to determine the tLim, t@VT2, and t@90%V̇O2peak tests. Blood lactate concentration ([La-]) was analyzed, and rate of perceived exertion (RPE) was recorded. 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. V̇O2peak (55.2±5.6 ml·kg·min-1) was only reached in CT (100.7±3.1 %V̇O2peak). In addition, high V̇O2 values were reached at IT100 (96.4±4.2 %V̇O2peak). V̇O2peak was highly correlated with Peak-V̇O2 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 tLim (1013.6±496.6 vs. 256.2±60.3 s), distance (1277.3±638.1 vs. 315.9±63.3 m), t@VT2 (448.1±211.1 vs. 144.1±78.8 s), and t@90%V̇O2peak (321.9±208.7 vs. 127.5±77.1 s). V̇O2K 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, tLim 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 V̇O2peak 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 tLim, t@VT2, and t@90%V̇O2peak (~757, ~304, and ~194 s more, respectively), without differing regards to [La-] and RPE. The V̇O2K seemed not to influence tLim and times spent near V̇O2peak in both workout modes.