O objetivo do presente estudo foi correlacionar as velocidades de limiar anaeróbio (LAn) obtidas a partir de concentrações fixas de lactato (VLAn 4 e VLAn 3,5mM), velocidade de lactato mínimo (VLac min) e velocidade crítica (VC) determinada a partir de diferentes distâncias e número de coordenadas: VC1 (50/100/200m), VC2 (100/200/400m), VC3 (50/100/200/400m) e VC4 (200/400m) com o desempenho nos 400m(s) em nadadores adolescentes. Fizeram parte da amostra 15 nadadores (10 meninos e cinco meninas = 14,7 ± 0,7 anos; 61,9 ± 8,5kg; 171,1 ± 8,8cm) de nível nacional, com experiência entre cinco e sete anos na natação competitiva. Para análise das correlações entre os índices e o desempenho nos 400m(s) foi utilizado o coeficiente de correlação de Pearson. O nível de significância adotado foi de p < 0,01. As correlações entre a VLAn 4mM, VLAn 3,5mM, VLac min e o desempenho nos 400m(s) foram de r = -0,63, r = -0,90 e r = -0,91, respectivamente (p < 0,01). As correlações entre a VC1 (50/100/200m), VC2 (100/200/400m), VC3 (50/100/200/400m), VC4 (200/400m) e o desempenho nos 400m(s) foram: r = -0,62, r = -0,97, r = -0,98 e r = -0,94, respectivamente (p < 0,01). Sugere-se que o LAn determinado a partir da concentração fixa de lactato de 3,5mM, bem como a VLac min e a VC obtidas por meio de distâncias maiores parecem ser os mais adequados índices preditores do desempenho aeróbio nos nadadores adolescentes estudados. Além disso, o número de coordenadas parece não influenciar a relação entre a VC e desempenho aeróbio.
The aim of the study was to investigate the effects of caffeine intake on anaerobic performance and rate of muscle fatigue in young men and women. Methods: Fourteen recreationally active college students volunteered to the study (7 male, 29.1 ± 2.8 у and 7 female, 22.5 ± 2.9 y) (73.06 ± 13.08 Kg, 173.00 ± 6.90 cm, 24.08 ± 3.01 Kg/m 2). The participants performed the Wingate Test (WT) to evaluate the anaerobic performance in two conditions: caffeine (CAF), ingesting 6mgKg-1 of caffeine, and placebo (PL), in random order. The variables analyzed during the WT were the Relative Peak Power (W-Kg-1) (RPP), Relative Mean Power (WKg-1) (RMP), Fatigue Index (%) (Fl) and Peak Power Instant (s) (PPI). EMG signals were analyzed using the Normalized Median Frequency (NMF) to determine the rate of muscle fatigue of the superficial muscles of the Quadriceps Femoris (QF), Rectus Femoris (RF), Vastus Medialis (VM) and Vastus Lateralis (VL). Data analysis was performed using the Student's t test and the two-way AN OVA for repeated measures, followed by the Sheffe post-hoc to compare the results. Results: Caffeine intake had no effect on anaerobic performance parameters (RPP, RMP, Fl and PPI) when compared with placebo (p > 0.05). The rate of muscle fatigue did not change with caffeine intake in the muscles studied (p > 0.05). Conclusions: Although caffeine may influence endurance and power in short-term, intense exercise; we did not observe such effects in the variables measured in this study.
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