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=13

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=<p>The time sustained during exercise with oxygen uptake (V̇O<sub>2</sub>) reaching maximal rates (V̇O<sub>2peak</sub>) or near peak responses (i.e., above second ventilatory threshold [t@VT<sub>2</sub>) or 90% V̇O<sub>2peak</sub> (t@90%V̇O<sub>2peak</sub>)] is recognized as the training pace required to enhance aerobic power and exercise tolerance in the severe domain (time-limit, t<sub>Lim</sub>). 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 V̇O<sub>2peak</sub>, VT<sub>2</sub>, and MAV assessments. Two other tests were performed in randomized order, to compare continuous (CT) vs. intermittent trials (IT<sub>100</sub>) at MAV until exhaustion, to determine peak oxygen uptake (Peak-V̇O<sub>2</sub>) and V̇O<sub>2</sub> kinetics (V̇O<sub>2</sub>K). Distance and time variables were registered to determine the t<sub>Lim</sub>, t@VT<sub>2</sub>, and t@90%V̇O<sub>2peak</sub> tests. Blood lactate concentration ([La<sup>−</sup>]) 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. V̇O<sub>2peak</sub> (55.2 ± 5.6 ml·kg·min<sup>−1</sup>) was only reached in CT (100.7 ± 3.1 %V̇O<sub>2peak</sub>). In addition, high V̇O<sub>2</sub> values were reached at IT<sub>100</sub> (96.4 ± 4.2 %V̇O<sub>2peak</sub>). V̇O<sub>2peak</sub> was highly correlated with Peak-V̇O<sub>2</sub> during CT (<italic>r</italic> = 0.95, <italic>p</italic> &lt; 0.01) and IT<sub>100</sub> (<italic>r</italic> = 0.91, <italic>p</italic> &lt; 0.01). Compared with CT, the IT<sub>100</sub> presented significantly higher values for t<sub>Lim</sub> (1,013.6 ± 496.6 vs. 256.2 ± 60.3 s), distance (1,277.3 ± 638.1 vs. 315.9 ± 63.3 m), t@VT<sub>2</sub> (448.1 ± 211.1 vs. 144.1 ± 78.8 s), and t@90%V̇O<sub>2peak</sub> (321.9 ± 208.7 vs. 127.5 ± 77.1 s). V̇O<sub>2</sub>K time constants (IT<sub>100</sub>: 25.9 ± 9.4 vs. CT: 26.5 ± 7.5 s) were correlated between tests (<italic>r</italic> = 0.76, <italic>p</italic> &lt; 0.01). Between CT and IT<sub>100</sub>, t<sub>Lim</sub> were not related, and RPE (8.9 ± 0.9 vs. 9.4 ± 0.8) and [La<sup>−</sup>] (7.8 ± 2.7 vs. 7.8 ± 2.8 mmol·l<sup>−1</sup>) did not differ between tests. MAV is suitable for planning swimming intensities requiring V̇O<sub>2peak</sub> rates, whatever the exercise schedule (continuous or intermittent). Therefore, the results suggest IT<sub>100</sub> as a preferable training schedule rather than the CT for aerobic capacity training since IT<sub>100</sub> presented a significantly higher t<sub>Lim</sub>, t@VT<sub>2</sub>, and t@90%V̇O<sub>2peak</sub> (∼757, ∼304, and ∼194 s more, respectively), without differing regards to [La<sup>−</sup>] and RPE. The V̇O<sub>2</sub>K seemed not to influence t<sub>Lim</sub> and times spent near V̇O<sub>2peak</sub> in both workout modes.</p>