Untitled

Abstract

The purpose of the present study was to compare the load influence on the time under tension (TUT), electromyographic activity (EMG) and blood lactate concentration (LAC) in 8, 10, and 12RM and the relationship between the TUT and the number of repetitions in the squat exercise. The sample consisted of ten military men (age: 18.90 ± 0.32 years, height: 1.73 ± 0.05 m, body mass: 67.55 ± 4.96 kg, body fat: 6.54 ± 1.87%). The TUT for 8, 10, and 12RM was verified by kinematic using the timing technique of the Kinovea software. After 48 hours, the subjects performed the squat exercise with the TUT and the load obtained in the tests, where the EMG and LAC were evaluated. The electrodes to capture the EMG signal were positioned in the following muscles: vastus medialis (VM), vastus lateralis (VL), rectus femoris (RF), and femoral biceps (FB). The ANOVA showed significant differences in all protocols in the TUT and LAC variables (p < 0.05) in increasing order to the number of repetitions (8 RM < 10RM < 12RM). The EMG showed a significant reduction in the RF activation in the 10RM for the 12RM in comparison with 8RM, as well as at VL activation for the 8 and 12RM protocols in comparison with 10RM. The study concluded that smaller loads and higher numbers of repetitions generate higher TUT and LAC. However, they result in smaller muscle activation for RF and VL. According to the results of the present study, there is no difference between 8, 10 and 12RM for the VM and FB muscles in the squat exercise.

Effects of the back-squat exercise on lower limb myoelectric activity in trained men: a systematic review

“…However, general muscle myoelectric activities amplified with increasing loads, but significant increases in EMG signals were observed only in the vastus medialis (VM) and gluteus maximus (GM) muscles with 90% and 100% of 1RM loads. Likewise, Silva et al [18] when submitted the sample to the squat exercise, observed an increase in the EMG activity of the GM and VM with increasing loads of 60% to 90% of 1RM.…”

“…The purpose of this systematic review was to describe the effects of the back squat exercise on the lower limb myoelectric activity in trained men. The analysis of the eight cross-sectional studies [12][13][14][15][16][17][18][19] showed greater muscle myoelectric activity during different squat protocols, but these do not represent a greater strength gain promoted by the type of exercise (p < 0.05).…”

“…Table III shows the studies' risk of bias through the ROBINS-I tool. Regarding the studies analyzed using the ROBINS-I tool, 70% [13,15,16,17,19] were considered with critical risk of bias, while only 30% [12,14,18] were considered with moderate risk of bias.…”

“…As for the interventions, five studies used the RT through free weights with bars and washers [12][13][14][15]19], two [16,17] used barbell and the Smith Machine, and one study [18] did not describe the device used. Furthermore, two of these studies [12,14] performed the RM tests in the back-squat exercise, adding the knee pad.…”

“…Furthermore, two of these studies [12,14] performed the RM tests in the back-squat exercise, adding the knee pad. One of these studies [18] performed the 1RM test with loads of 80%, 90%, and 100%, using the EMG in the back squat exercise. However, general muscle myoelectric activities amplified with increasing loads, but significant increases in EMG signals were observed only in the vastus medialis (VM) and gluteus maximus (GM) muscles with 90% and 100% of 1RM loads.…”