Neuromuscular activation and RPE in the quadriceps at low and high isometric intensities

Introduction. The purpose of this study was to examine neuromuscular activation and ratings of perceived exertion (RPE) at 10 %o and 80 % quadriceps MVC in healthy males. Methods. Seventeen college-aged volunteers (mean age = 22.6 years, mean height = 178.9 cm, mean weight = 78.8 kg) were assessed for isometric EMG activity of the vastus medialis (VM) and vastus lateralis (VL) at 10 % and 80 % MVC, and RPE at 80 % MVC. Perceived exertion was measured with a modified category ratio scale (CR-10) and was anchored with 1 high and 1 low anchor. Raw EMG signals were sampled via telemetry (rate = 1,000 Hz) and integrated (3 sec) for each contraction for each muscle (bandpass = 16-500 Hz, CMRR = 130 dB). A one-sample t-test was performed for each variable and 95 % confidence intervals were calculated. Results. Means and CI for each variable are as follows: 10% MVC VM IEMG (t ₁₆ =5.05, p < 0.001, .95 CI = 3.11 ± 1.3), 80 % MVC VM IEMG (t ₁₆ = 22.51, p < 0.001, .95 CI = 73.2 ± 6.89), 10 % MVC VL IEMG (t ₁₆ =8.10, p < 0.001, .95 CI=9.41 ± 2.47), 80% MVC VL IEMG (t ₁₆ =39,56, p < 0.001, .95 CI = 87.32 ± 4.68), and 80 % MVC RPE (t ₁₆ = 11.85, p < 0.001, .95 CI = 5.24 ± 0.93). Discussion. The major findings illustrate an apparent underestimation of RPE at 80 % MVC for the quadriceps. Neuromuscular activation appears to be lower than the expected force output at both intensities for the VM while VL activation corresponded closely at 10 % MVC and was higher at 80 % MVC.