Objective: Delay onset of the vastus medialis obliquus (VMO) has often been reported to happen in people with patellofemoral pain (PFP). Previous studies revealed that motion control shoe could check rearfoot pronation in overpronators. Literature suggested that movements of the lower leg could affect patellar tracking, thus motion control shoe may help prevent PFP by controlling excessive foot movements. This study aimed to compare the vasti muscle activities in people with excessive foot pronation when running with different footwear.
Methods: Twenty female subjects with rearfoot pronation >6o were tested by running for 10 km on a treadmill on 2 separate days. During each test, subjects either wore motion control running shoe or neutral running shoe. EMG activities of their right VMO and vastus lateralis (VL) were recorded. Their EMG onset timing and median frequency (MF) were compared between the two shoe conditions.
Results: A significant delay in VMO onset of the running duty cycle was observed in the neutral shoe condition than the motion control shoe (p<0.001). In neutral shoe condition, the delay in VMO increased with running mileage (Pearson correlation = 0.948) whereas no such pattern was observed in the motion control shoe. Significant drop in MF of the quadriceps after the 10-km run in both shoe conditions was observed (p ranged <0.001 to 0.008), and there was a larger drop in VMO MF when running with neutral shoe.
Conclusions: The findings suggest that motion control shoe may facilitate a stable temporal activation of VMO during running.