EFFECTS OF STRETCHING EXERCISES ON VASTUS MEDIALIS AND VASTUS LATERALIS

Abstract

A concern of post-knee-surgery rehabilitation is strengthening the vastus medialis muscle to avoid muscle imbalance between the vastus lateralis muscle. The purpose of this pilot study was to investigate the effects of knee exercises and proprioceptive neuromuscular facilitation (PNF) on the electromyography (EMG) response of four muscles, vastus medialis (VMO), vastus medialis longus (VML), vastus lateralis (VL), and rectus femoris (RF), under isometric contraction conditions. Five healthy male subjects, (mean age = 28.4 yr, height = 174.8 cm, and weight = 68.7 kg) with no knee pathology volunteered to participate. Four knee stretching exercises, straight leg raise (SLR), ankle dorsi flexion/inversion (DI), internal rotation (IR), and adduction (ADD) and one PNF technique, ankle dorsi flexion/inversion with hip flexion/adduction, were performed on the right lower extremity with the knee extended. A 5-second maximal muscle contraction followed each stretching exercise. Three trials of each stretching exercise were completed in a random order with a 30-second-rest period between trials. The hypothesis was that the PNF technique would enhance VMO and VML activity compared to the other stretching exercises. A repeated measures ANOVA and Tukey HSD post hoc test was used with alpha levels set at .05. For the VMO, VML, and VL muscles, significant differences were found between the PNF and SLR conditions and between the PRN and DI conditions. For The RF muscle, there were significant differences between ADD and PNF, SLR, DI, and IR. The SLR and DI conditions produced a greater EMG response for all the muscles compared to the IR, and ADD knee exercises. The RF muscle's greatest response was associated with the IR exercise and the smallest response was associated with the ADD exercise. The DI and SLR exercises showed similar muscle EMG responses for all the muscles. It was concluded that the PNF technique showed greater recruitment of the VMO, VML, VL, and RF muscles compared to SLR, DI, IR, and ADD stretching techniques.