Efeito de diferentes protocolos de cargas incrementais sobre as respostas eletromiográficas e lactato sanguíneo durante exercício dinâmico descontínuo e resistido em corredores fundistas moderadamente treinados

Abstract

The anaerobic threshold (AT) has been considered a reliable index to measure the intensity domains during exercising, and it can be identified through blood lactate concentrations [Lac] and through surface electromyography (sEMG). The main objectives of this study were: (a) to identify and to correlate the electromyographic threshold (EMGTH) and the lactate threshold (LT) during incremental protocols performed on a treadmill (IT) and on the leg press 45° (LP 45°) exercise; and (b) to correlate the values of [Lac] in which the AT was identified among the incremental protocols performed in IT and LP 45°. Twelve male long-distance runners, moderately trained, were volunteers (age = 29.27 ± 3.24 years; body fat percentage = 10.33 ± 2.62 %; height = 1.77 ± 0.04 m; body mass = 73.44 ± 4.38 kg; time of 5000 m = 20 min and 37.8 sec ± 2 min and 21 sec; training time = 4.26 ± 0.68 years). Shortly after the preliminary evaluation sessions, volunteers were randomized to perform two distinct incremental protocols running on IT and LP 45°, in which the EMG signal and blood lactate were collected during the end of each stage in both proposed exercises. Statistical tests of normality and homogeneity of variance were performed, in addition to two-way Anova test with Post Hoc Bonferroni, T for independent samples, Pearson correlation and Bland Altman, adopting the significance level p ≤ 0.05. The results showed no significant differences between the running speed and the exercise intensity in which LT and EMGTH were identified in both protocols. In the IT and in the LP 45º were observed correlations and agreements between LT and EMGTH. No significant differences were observed among the values of [Lac], in which the AT was identified in IT and LP 45°. The incremental protocols showed agreement. The results highlighted the applicability of sEMG as a non-invasive tool for determining the AT. Although there is agreement between the values of [Lac] where the AT was determined in EE and LP 45°, further studies are still needed with more elaborate methodologies that would confirm that premise.