Study of muscular fatigue by EMG analysis during isometric exercise

Ten female individuals (age = 21 ± 2 years; weight = 50 ± 2 kg; height = 160 ± 3 cm) were analyzed. For the determination of the electromyographic fatigue threshold (EMGft), four percentages of load (10, 20, 30 and 40%), in relation the maximum voluntary contraction (MVC) were used, until the subjective exhaustion. The biosignals in these percentages had been linearly adjusted in domain of the number of repetition in which the slopes were obtained. These numbers had been correlated with its respective percentages of load, where the y-intercept of this linear regression corresponds to the EMGft. The isometric training consisted of the performing of 15 maximum repetitions with an interval of 2 minutes being carried through 3 times per weeks during 4 weeks. The results demonstrated that there is a significant increase (p<;0.05) of the MVC after training (167.10 ± 33.87 N) in relation the MVC before training (132.17 ± 31.74 N). The value of the EMG_FT increased for the semitendinosus (ST) muscle from 18.89 to 21.06% and it remained similar for the biceps femoris (caput longum) (BFCL) muscle from 20.4 to 19.90% where these variations had not been significantly different (p<;0.05). Thus, the isometric training was efficient to further increase of the MVC however it did not influence the value of the EMG_FT of these muscles.