Effects of Lift Velocity on Muscle Activation During Leg Extension

Abstract

It is not known if manipulating velocity within a prescribed resistance training mode will improve muscle activation. Muscle activations of the Rectus Femoris (RF), Vastus Lateralis (VL), Vastus Medialis (VM) and Bicep Femoris (BF) were examined during a leg extension exercise at 3 different velocities on 15 subjects (10men, 5 female, Age = 21.5 ± 1.8 yrs, Height = 171.2 ± 12.5 cm, Mass = 75.5 ± 16.3 kg). Trials of 1 set of 10 repetitions at 60% of 1RM, were performed at 15, 30 and 60o/s. Bipolar surface electrodes were placed over the BF, RF, VL, and VM. Micro-switches were utilized to identify the concentric (CON) and eccentric (ECC) phases of the lift. Data were sampled at 1024 Hz, filtered, rectified and the mean, integrated EMG calculated. One 2 x 4 x 3 (action x muscle x velocity) ANOVA with bonferonni adjustment was run and significance was followed by Tukey HSD post hoc analysis. Results indicated significantly greater activation of the VL, RF and VM for ECC extension at 60o/s compared to 15o/s. While 60o/s was also greater than 30o/s for the VL and VM during ECC. While comparing muscle action, CON VL, VM and RF were greater than ECC at 30o/sec, meanwhile VM CON was also greater at 15o/sec. No differences in muscle activation at any velocity or muscle action for BF were identified. We conclude that muscle recruitment while training with a 60% 1RM load is maximized at a velocity of 60o/s during ECC activity and 15 or 30o/sec during CON.