The reliability of back-extrapolation in estimating V ˙ O 2 p e a k in different swimming performances at the severe-intensity domain.

The amount of anerobic energy released during exercise might modify the initial phase of oxygen recovery (fast-O _2debt ) post-exercise. Therefore, the present study aimed to analyze the reliability of peak oxygen uptake ( V ˙ O 2 p e a k ) estimate by back-extrapolation ( B E - V ˙ O 2 p e a k ) under different swimming conditions in the severe-intensity domain, verifying how the alterations of the V ˙ O 2 recovery profile and anerobic energy demand might affect B E - V ˙ O 2 p e a k values. Twenty swimmers (16.7 ± 2.4 years, 173.5 ± 10.2 cm, and 66.4 ± 10.6 kg) performed an incremental intermittent step protocol (IIST: 6 × 250 plus 1 × 200 m, IIST&#95;v200m) for the assessment of V ˙ O 2 p e a k . The V ˙ O 2 off-kinetics used a bi-exponential model to discriminate primary amplitude, time delay, and time constant (A _1off , TD _1off , and τ _off ) for assessment of fast-O _2debt post IIST&#95;v200m, 200-m single-trial (v200 m), and rest-to-work transition at 90% delta (v90%Δ) tests. The linear regression estimated B E - V ˙ O 2 p e a k and the rate of V ˙ O 2 recovery (BE-slope) post each swimming performance. The ANOVA (Sidak as post hoc ) compared V ˙ O 2 p e a k to the estimates of B E - V ˙ O 2 p e a k in v200 m, IIST&#95;v200 m, and v90%Δ, and the coefficient of dispersion (R ² ) analyzed the association between tests. The values of V ˙ O 2 p e a k during IIST did not differ from B E - V ˙ O 2 p e a k in v200 m, IIST&#95;v200 m, and v90%Δ (55.7 ± 7.1 vs. 53.7 ± 8.2 vs. 56.3 ± 8.2 vs. 54.1 ± 9.1 ml kg ^-1  min ^-1 , p > 0.05, respectively). However, the V ˙ O 2 p e a k variance is moderately explained by B E - V ˙ O 2 p e a k only in IIST&#95;v200 m and v90%Δ (R _Adj ² = 0.44 and R _Adj ² = 0.43, p < 0.01). The TD _1off and τ _off responses post IIST&#95;v200 m were considerably lower than those in both v200 m (6.1 ± 3.8 and 33.0 ± 9.5 s vs. 10.9 ± 3.5 and 47.7 ± 7.9 s; p < 0.05) and v90%Δ ( 10.1 ± 3.8 and 44.3 ± 6.3 s, p < 0.05). The BE-slope post IIST&#95;v200m was faster than in v200 m and v90%Δ (-47.9 ± 14.6 vs. -33.0 ± 10.4 vs. -33.6 ± 13.8 ml kg ^-1 , p < 0.01), and the total anerobic (Anaer _Total ) demand was lower in IIST&#95;v200 m (37.4 ± 9.4 ml kg ^-1 ) than in 200 m and 90%Δ (51.4 ± 9.4 and 46.2 ± 7.7 ml kg ^-1 , p < 0.01). Finally, the τ _1off was related to Anaer _Total in IIST&#95;v200m, v200 m, and v90%Δ (r = 0.64, r = 0.61, and r = 0.64, p < 0.01). The initial phase of the V ˙ O 2 recovery profile provided different (although reliable) conditions for the estimate of V ˙ O 2 p e a k with BE procedures, which accounted for the moderate effect of anerobic release on V ˙ O 2 off-kinetics, but compromised exceptionally the V ˙ O 2 p e a k estimate in the 200-m single trial.
Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
(Copyright © 2022 Massini, Simionato, Almeida, Macedo, Espada, Reis, Besone Alves and Pessôa Filho.)