ELECTROMYOGRAPHIC ANALYSIS OF THE VMO/VL RATIO ON STABLE VS. UNSTABLE SURFACES
Patellofemoral pain syndrome (PFPS) is associated with anterior knee pain and patella mal-tracking. A number of studies suggest that one cause of patella mal-tracking is low vastus medialis obliquus (VMO) activation relative to the vastus lateralis (VL) activation (VMO/VL). Most research points towards different quad strengthening exercises to increase the VMO/VL activation ratio, but the best exercises to do this remain controversial. PURPOSE: The purpose of the present study is to compare unilateral and bilateral squats on stable and unstable surfaces to determine which results in the highest VMO/VL muscle activation. METHODS: Electromyography (EMG) electrodes were placed on the muscle bellies of the VMO and VL. The subjects performed three trials of double leg and single leg squats on two different surfaces: the stable ground and a Bosu ball. The order of these trials were randomized for each subject. All EMG data was normalized using the EMG values from the double leg squat. A two-way within subjects ANOVA was conducted that examined the effect of surface type and the number of legs on the VMO, VL, and VMO/VL activation during a squat. RESULTS: The highest VMO activation occurred during the single leg on Bosu ball (B1) trial (2.31±0.60), followed by single leg on the ground (G1) (2.17±0.55), double leg on Bosu ball (B2) (1.12±0.28), and then double leg on the ground (G2) (1.00±0.00). There was no significant difference in the muscle activation between surface types (F(1, 19) = 4.91, p = 0.06); however, there was a significant difference in muscle activation between single and double leg squat (F(1, 19) = 111.48, p < 0.01). There was no statistically significant difference in the interaction between the effects of the surface type and number of legs on the VMO activation (F(1, 19) = 0.03, p = 0.86). Additionally, the analysis that examined the effect of surface type and the number of legs on the VMO/VL ratio during a squat revealed that there was no statistically significant difference in muscle activation between surface types (F(1, 19) = 2.07, p = 0.17), single and double leg squats (F(1, 19) = 3.50, p = 0.08), and no significant difference in the interaction between the effects of the surface type and number of legs on the VMO/VL ratio (F(1, 19) = 0.81, p = 0.38). CONCLUSION: Although the VMO/VL ratio was not statistically significantly different among trials, VMO activation did increase from the bilateral trials to the unilateral trials. Ultimately, additional studies with larger sample sizes should further investigate the VMO/VL activation during single leg squats, specifically in patients with PFPS.
Smith, E.; Napier, M.; Miller, A.; Wrolstad, K.; and Higginson, B.
"ELECTROMYOGRAPHIC ANALYSIS OF THE VMO/VL RATIO ON STABLE VS. UNSTABLE SURFACES,"
International Journal of Exercise Science: Conference Proceedings: Vol. 8
, Article 33.
Available at: http://digitalcommons.wku.edu/ijesab/vol8/iss5/33
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