Effects of Different Neuromuscular Electrical Stimulation Parameters on Quadriceps Neuromuscular Performance in Competitive Athletes
Résumé
PURPOSE: To evaluate the effects of six weeks of training with two different types of neuromuscular electrostimulation (NMES) currents on muscle performance in competitive athletes.
METHODS: This controlled and randomized clinical trial included 20 athletes, equally divided into three groups: medium frequency current group with 500 μs (MF-500) (n=7), low frequency current group of with 500 μs (PC-500) (n=5) and control group (CG) (n=8). Each group had evaluated, before and after the intervention: the peak torque of knee (PT), muscle thickness and signs of electromyography (EMG) of the vastus lateralis (VL), and the sensory discomfort level (VAS). The training with NMES was performed 3 times per week and consisted of 18 sessions, 15 minutes per session (36 isometric involuntary contractions per session), 6s duration in each contraction (with 1s rise time - TON and 1s descent time - TOFF). For statistical analysis of homogeneity was applied Levene’s test. Mixed ANOVA test was used to verify the existence of significant differences between the measurements. The significance level was 5%.
RESULTS: There was no significant difference between any groups for all variables (p > 0.05): PT (MF500: pre = 222.5 ± 42.2 Nm and post = 219.9 ± 54 Nm; PC500: pre = 231.1 ± 82.2 Nm and post = 244.3 ± 79, 9 Nm; CG: pre = 243 ± 40.1 Nm and post = 225.3 ± 43.2 Nm), muscle thickness (MF500: pre = 22.9 ± 2.5 mm and post = 23.7 ± 2.8 mm; PC500: pre = 23 ± 2.6 mm and post = 23.5 ± 2.7 mm; CG: pre = 25.9 ± 4.7 mm and post = 25.9 ± 4.3 mm) and EMG (MF500: pre = 0.4 ± 0.4 RMS and post = 0.5 ± 0.5 RMS; PC500: pre = 0.7 ± 0.4 RMS and post = 0.7 ± 0.3 RMS; CG: pre = 0, 8 ± 0.5 RMS and post = 0.7 ± 0.4 RMS). In addition, all current produced similar levels of discomfort, with no significant difference (p > 0.05) in the VAS (MF500: pre = 9.6 ± 0.5 and post = 9.1 ± 1.5; PC500: pre = 9.8 ± 0.5 and post = 9.4 ± 1.3).
CONCLUSION: The NMES training applied with medium or low frequency currents and the same pulse duration have the same efficiency and neuromuscular performance in the quadriceps of competitive athletes.