Optimization of the position for isometric exercise to strengthen the vastus medialis oblique muscle based on surface electromyography tests: an observational study

Background
The vastus medialis oblique (VMO) is the main dyna- mic stabilizer of the knee joint. Due to its anatomic structure, the muscle works at high speed and with high strength, but it tends to weaken relatively fast and atrophy.

Aims
The study aimed to determine if vastus medialis muscle (VM) shows the highest bioelectric activity during isometric contraction in flexion or extension position of the knee joint.

Material and methods
Tests were conducted on 48 cases; the bio- electrical activity of the VM muscle was measured with the use of surface electromyography (sEMG). The electric potentials of the muscle were tested in two positions of the knee joint extension from 5° to 0° and flexion of 90°. Tests were conducted three times in each of the positions. The statistical analysis was based on two analyzed parameters: the average value of excitation and the maxi- mum value of excitation of the vastus medialis muscle.

Results
The VMO muscle shows a higher bioelectric activity in the extended position of the knee joint than when the joint is flexed, in a statistically significant way (p<0.01). The result is significant for both the average and the maximum muscle activation values.

Conclusions
In the extended position of the knee joint, the vastus medialis muscle shows the highest bioelectric activity during iso- metric contraction, which makes it the best position for isometric exercise to strengthen this muscle.