| Abstrakt: |
The amount of anerobic energy released during exercise might modify the initial phase of oxygen recovery (fast-O2debt) post-exercise. Therefore, the present study aimed to analyze the reliability of peak oxygen uptake (V̇O2peak) estimate by back-extrapolation (BE −V̇O2peak under different swimming conditions in the severe-intensity domain, verifying how the alterations of the V̇O2 recovery profile and anerobic energy demand might affect BE − V̇O2peak 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_v200m) for the assessment of V̇O2peak. The V̇O2 off-kinetics used a biexponential model to discriminate primary amplitude, time delay, and time constant (A1off, TD1off, and τoff) for assessment of fast-O2debt post IIST_v200m, 200-m single-trial (v200 m), and rest-to-work transition at 90% delta (v90%Δ) tests. The linear regression estimated BE − V̇O2peak and the rate of V̇O2 recovery (BE-slope) post each swimming performance. The ANOVA (Sidak as post hoc) compared V̇O2peak to the estimates of BE − V̇O2peak in v200m, IIST_v200 m, and v90%Δ, and the coefficient of dispersion (R²) analyzed the association between tests. The values of V̇O2peak during IIST did not differ from BE − V̇O2peak in v200 m, IIST_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−1min−1, p > 0.05, respectively). However, the V̇O2peak variance is moderately explained by BE − V̇O2peak only in IIST_v200 m and v90%Δ (R²Adj = 0.44 and R² Adj = 0.43, p < 0.01). The TD1off and τoff responses post IIST_v200 m were considerably lower than those in both v200m (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_v200m was faster than in v200m 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 (AnaerTotal) demand was lower in IIST_v200 m(37.4 ± 9.4 ml kg−1) than in 200m and 90%Δ (51.4 ± 9.4 and 46.2 ± 7.7 ml kg−1, p < 0.01). Finally, the τ1off was related to AnaerTotal in IIST_v200m, v200 m, and v90%Δ (r = 0.64, r = 0.61, and r = 0.64, p < 0.01). The initial phase of the V̇O2 recovery profile provided different (although reliable) conditions for the estimate of V̇O2peak with BE procedures, which accounted for the moderate effect of anerobic release on V̇O2 off-kinetics, but compromised exceptionally the V̇O2peak estimate in the 200-m single trial. [ABSTRACT FROM AUTHOR] |
