ABSTRACT
O objetivo foi comparar a magnitude do efeito protetor (EP) contra o dano muscular (DM) induzido por uma sessão de exercícios excêntricos (EEM) entre os extensores do joelho e os flexores do cotovelo. Doze sujeitos do gênero masculino foram divididos em 2 grupos, braços (GB) e pernas (GP), e realizaram 2 sessões de EEM. Foram coletados 3 marcadores de DM, sendo eles, pico de torque isométrico (PTI), creatina quinase (CK) e percepção subjetiva de dor (PSD), antes, imediatamente após (com exceção da CK) e 48 horas após cada sessão de EEM. Foi encontrada queda significante de PTI e aumento significante de CK e PSD tanto imediatamente e 48 horas após a primeira sessão de EEM para o GB. No GP houve aumento significante de CK 48 horas após os EEM e da PSD imediatamente após os EEM, decorrentes da primeira sessão. No GB, a segunda sessão apenas provocou queda de PTI imediatamente após os EEM, enquanto no GP houve aumento significante apenas na PSD imediatamente após a segunda sessão de EEM. Apenas a CK apresentou EP para ambos os grupos. Pudemos concluir que o EP foi maior para o GB em comparação com o GP. Esse fenômeno pode ter ocorrido em detrimento da existência de um EP prévio para o GP, uma vez que este membro realiza contrações excêntricas intensas com maior freqüência no dia-a-dia, quando comparados com os GB.
The objective was to compare the magnitude of the repeated bout effect (RBE) induced by an eccentric exercise session (EES) between the knee extensors and elbow flexors. Twelve male subjects were divided into two groups, arms (AG) and legs (LG), and executed two EES. We collected three markers of muscle damage, they were, isometric peak torque (IPT), creatine kinase (CK) and subjective perception of pain (PSD) before, immediately after (except CK) and 48 hours after each EES. Significant decrease in PTI was found as well as significant increase in CK and PSD both immediately and 48 hours after the first EES for the AG. In the LG there was a significant increase in CK 48 hours after, and PSD immediately after the first EES. In the AG, the second EES caused a drop of only PTI immediately after it, while the LG presented a significant increase only in PSD immediately after the second EES. RBE was found only for CK in both groups. We concluded that the RBE was higher in the AG compared to the LG. This phenomenon may have occurred over the existence of a protection for the LG, since this member performs intense eccentric contractions more frequently in day-to-day, compared to AG.
Subject(s)
Humans , Male , Exercise , Lower Extremity , Motor Activity , Upper ExtremityABSTRACT
Skeletal muscle force production following repetitive contractions is preferentially reduced when muscle is evaluated with low-frequency stimulation. This selective impairment in force generation is called low-frequency fatigue (LFF) and could be dependent on the contraction type. The purpose of this study was to compare LFF after concentric and eccentric maximal and submaximal contractions of knee extensor muscles. Ten healthy male subjects (age: 23.6 ± 4.2 years; weight: 73.8 ± 7.7 kg; height: 1.79 ± 0.05 m) executed maximal voluntary contractions that were measured before a fatigue test (pre-exercise), immediately after (after-exercise) and after 1 h of recovery (after-recovery). The fatigue test consisted of 60 maximal (100 percent) or submaximal (40 percent) dynamic concentric or eccentric knee extensions at an angular velocity of 60°/s. The isometric torque produced by low- (20 Hz) and high- (100 Hz) frequency stimulation was also measured at these times and the 20:100 Hz ratio was calculated to assess LFF. One-way ANOVA for repeated measures followed by the Newman-Keuls post hoc test was used to determine significant (P < 0.05) differences. LFF was evident after-recovery in all trials except following submaximal eccentric contractions. LFF was not evident after-exercise, regardless of exercise intensity or contraction type. Our results suggest that low-frequency fatigue was evident after submaximal concentric but not submaximal eccentric contractions and was more pronounced after 1-h of recovery.