RESUMO
This study aimed to investigate the effects of chronic ß-alanine (ßA) plus acute sodium bicarbonate (SB) co-supplementation on neuromuscular fatigue during high-intensity intermittent efforts in swimming. Eleven regional and national competitive-level young swimmers performed a neuromuscular fatigue assessment before and immediately after two 20 × 25-m front crawl maximal efforts every 90 s, performed at pre- and post-4-week co-supplementation. Neuromuscular fatigue was evaluated by percutaneous electrical stimuli through the twitch interpolation technique on the triceps brachii and quadriceps femoris. Performance was defined by the mean time of the 20 efforts and blood samples to lactate concentrations were collected every four efforts. Participants supplemented 3.2-6.4 g·day-1 of chronic ßA or placebo (PL) during four weeks, and acute 0.3 g·kg-1 of SB or PL 60 min before the second assessment (allowing ßA+SB and PL+PL groups). No statistical changes were found in neuromuscular fatigue of triceps brachii. In the quadriceps femoris, a main effect of time was found in potentiated twitch delta values in pooled groups, showing a statistical increase of 19.01% after four weeks (Δ = 13.05 [0.35-25.75] N; p = 0.044), without time × group interactions. No statistical difference was found in the swimming performance. Blood lactate increased by 25.06% only in the ßA+SB group (Δ = 6.40 [4.62-8.18] mM; p Bonf < 0.001) after the supplementation period. In conclusion, 4-week ßA and SB co-supplementation were not able to reduce neuromuscular fatigue levels and improve performance in highintensity intermittent efforts, but statistically increased blood lactate levels.
RESUMO
This study investigated whether a heavy-intensity priming exercise precisely prescribed within the heavy-intensity domain would lead to a greater peak-power output (POpeak) and a longer maximal oxygen uptake (VÌo2max) plateau. Twelve recreationally active adults participated in this study. Two visits were required: 1) a step-ramp-step test [ramp-incremental (RI) control], and 2) an RI test preceded by a priming exercise within the heavy-intensity domain (RI primed). A piecewise equation was used to quantify the VÌo2 plateau duration (VÌo2plateau-time). The mean response time (MRT) was computed during the RI control condition. The delta (Δ) VÌo2 slope (S; mL·min-1·W-1) and VÌo2-Y intercept (Y; mL·min-1) within the moderate-intensity domain between conditions (RI primed minus RI control) were also assessed using a novel graphical analysis. VÌo2plateau-time (P = 0.001; d = 1.27) and POpeak (P = 0.003; d = 1.08) were all greater in the RI primed. MRT (P < 0.001; d = 2.45) was shorter in the RI primed compared with the RI control. A larger ΔVÌo2plateau-time was correlated with a larger ΔMRT between conditions (r = -0.79; P = 0.002). This study demonstrated that heavy-intensity priming exercise lengthened the VÌo2plateau-time and increased POpeak. The overall faster RI-VÌo2 responses seem to be responsible for the longer VÌo2plateau-time. Specifically, a shorter MRT, but not changes in RI-VÌo2-slopes, was associated with a longer VÌo2plateau-time following priming exercise.NEW & NOTEWORTHY It remains unclear whether priming exercise extends the maximal oxygen uptake (VÌo2max) plateau and increases peak-power output (POpeak) during ramp-incremental (RI) tests. This study demonstrates that a priming exercise, precisely prescribed within the heavy-intensity domain, extends the plateau at VÌo2max and leads to a greater POpeak. Specifically, the extended VÌo2max plateau was associated with accelerated RI-VÌo2 responses.
Assuntos
Exercício Físico , Consumo de Oxigênio , Humanos , Masculino , Consumo de Oxigênio/fisiologia , Adulto , Feminino , Adulto Jovem , Exercício Físico/fisiologia , Teste de Esforço , Fatores de Tempo , Músculo Esquelético/fisiologiaRESUMO
PURPOSE: This study aimed to investigate whether a ramp-to-constant WR (rCWR) transition compared with a square-wave-to-constant WR (CWR) transition within the heavy-intensity domain can reduce metabolic instability and decrease the oxygen cost of exercise. METHODS: Fourteen individuals performed (i) a ramp-incremental test to task failure, (ii) a 21-min CWR within the heavy-intensity domain, and (iii) an rCWR to the same WR. Oxygen uptake (VÌO 2 ), lactate concentration ([La - ]), and muscle oxygen saturation (SmO 2 ) were measured. VÌO 2 and VÌO 2 gain (VÌO 2 -G) during the first 10-min steady-state VÌO 2 were analyzed. [La - ] before, at, and after steady-state VÌO 2 and SmO 2 during the entire 21-min steady-state exercise were also examined. RESULTS: VÌO 2 and VÌO 2 -G during rCWR (2.49 ± 0.58 L·min -1 and 10.7 ± 0.2 mL·min -1 ·W -1 , respectively) were lower ( P < 0.001) than CWR (2.57 ± 0.60 L·min -1 and 11.3 ± 0.2 mL·min -1 ·W -1 , respectively). [La - ] before and at steady-state VÌO 2 during the rCWR condition (1.94 ± 0.60 and 3.52 ± 1.19 mM, respectively) was lower than the CWR condition (3.05 ± 0.82 and 4.15 ± 1.25 mM, respectively) ( P < 0.001). [La - ] dynamics after steady-state VÌO 2 were unstable for the rCWR ( P = 0.011). SmO 2 was unstable within the CWR condition from minutes 4 to 13 ( P < 0.05). CONCLUSIONS: The metabolic disruption caused by the initial minutes of square-wave exercise transitions is a primary contributor to metabolic instability, leading to an increased VÌO 2 -G compared with the rCWR condition approach. The reduced early reliance on anaerobic energy sources during the rCWR condition may be responsible for the lower VÌO 2 -G.
Assuntos
Teste de Esforço , Consumo de Oxigênio , Humanos , Consumo de Oxigênio/fisiologia , Exercício Físico/fisiologia , Ácido Láctico , OxigênioRESUMO
Aim: The present study aimed to verify if there is a difference between genders in anaerobic capacity estimated by energetic equivalents of glycolytic and phosphagen pathways (AC[La-]+EPOCfast). Methods: In this way, 8 men and 8 women (physical education students) were subjected to the following sequence of tests: session 1) graded exercise test to measure the maximal oxygen consumption (VÖ½ O2max) and intensity associated with VÖ½ O2max (iVÖ½ O2max); sessions 2 to 3) familiarization with supramaximal effort at 115% of iVÖ½ O2max; session 4) supramaximal effort at 115% of iVÖ½ O2max to measure AC[La-]+EPOCfast. Results: The AC[La-]+EPOCfast was lower in women compared to men when expressed in absolute and relative values (-38.11%; p=0.01 and -25.71%; p=0.03, respectively). A non-significant difference was observed in performance in the supramaximal effort (-12.08%; p=0.15), besides which, a likely negative inference was observed when comparing women to men. In addition, energetic equivalents of the glycolytic pathway (e[La- ]) were also lower in women when expressed in relative and absolute values (-47.01%; p=0.001 and -36.71%; p=0.001, respectively), however no statistical difference was found for energetic equivalents of the phosphagen pathway (ePCr) (p>0.05). Conclusion: The AC[La-]+EPOCfast is lower in women compared to men, mainly due to differences in the glycolytic pathway.(AU)