A Study on Quantification of Maximum Voluntary Contraction of Quadriceps at Various Functional Knee Range of Motion, Using Surface EMG (sEMG)

Quadriceps MVC and sEMG in Physiotherapy Education

Abstract

Objective: Surface electromyography (sEMG) is an essential tool in physiotherapy education, enabling students to objectively analyze muscle activation and understand joint-angle–dependent changes in force production. Teaching maximum voluntary contraction (MVC) assessment enhances clinical reasoning skills, accuracy of muscle testing, and evidence-based exercise prescription. This study evaluates quadriceps MVC at 70°, 90°, and 110° of knee flexion and highlights its educational relevance for physiotherapy training. Previous studies suggest that mid-range knee flexion allows optimal muscle activation, but comparative evidence across 70°, 90°, and 110° remains limited. Research using sEMG supports the idea that quadriceps activation changes with joint angle, yet findings are inconsistent. Therefore, examining individual differences in MVC at these specific angles is essential. Healthy participants aged 18-25 years who were free from knee injuries, musculoskeletal disorders, and neurological issues were included. All subjects were able to perform isometric quadriceps contractions and provided informed consent.
Methods: Forty-five healthy adults aged 18-25 years were assessed in a controlled laboratory setting. sEMG electrodes were placed over the vastus medialis oblique (VMO) and vastus lateralis (VL) muscles. MVC was recorded during isometric quadriceps contraction at knee flexion angles of 70°, 90°, and 110, which were measured using a universal goniometer. Statistical analysis included one-way analysis of variance, Bonferroni post-hoc tests, and paired t-tests.
Results: VMO and VL showed significant differences in MVC across all three knee angles (p < 0.001). Post-hoc analysis indicated significant differences between VMO 70- 90 and VMO 70-110, and between VL 70-90 and VL 70-110. Quadriceps composite activation showed no significant difference between 70°-90° and 70°-110°, while 90°-110° showed significant variation (p < 0.001). Mid-range knee flexion demonstrated the highest activation efficiency.
CONCLUSION: Quadriceps MVC is greatest between 70° and 90° of knee flexion. Integrating sEMG-based MVC assessment into physiotherapy education enhances students’ understanding of muscle biomechanics, objective evaluation, and optimal exercise positioning. This study supports the incorporation of technology-assisted EMG training into physiotherapy laboratory teaching to improve competency.