UBC Theses and Dissertations
Quadriceps muscle activity in female runners with patellofemoral pain syndrome MacIntyre, Donna Lee
The aim of this study was to determine if there was a difference in the surface EMG patterns of three of the quadriceps muscles (vastus medial is, vastus lateralis and rectus femoris) in female runners diagnosed with patellofemoral pain syndrome (PFPS) compared to the quadriceps activity of female runners free of knee pain and with normal lower extremity alignment. Linear envelope EMGs from vastus medial is, vastus lateralis and rectus femoris, together with a footswitch signal, were digitally recorded as each subject ran on a treadmill at 12 km/h. Each stride period was normalized to 100%, and then the linear envelopes for ten trials from each muscle were ensemble averaged to achieve a mean ensemble for each muscle from each subject. Subsequently, the grand mean ensemble of each muscle for all of the subjects in each group was computed. It was also the objective of this study to determine if there was a difference in the peak concentric and eccentric torques of the quadriceps and the hamstrings between the experimental group and the control group. The subjects were tested on an isokinetic dynamometer (KINCOM) through a range of 90° at an angular velocity of 200°/s. The results showed no statistically significant differences between the groups for the peak EMG amplitudes. In fact when comparing the EMG patterns of activity between the two groups, the grand ensemble average of the experimental group remained within ± one standard deviation of the control group's mean EMG pattern. However, when individual subjects with PFPS were compared to the control group, there were periods in the gait cycle when the EMG amplitude was outside of ± one standard deviation of the control group's mean. When comparing the two groups for the peak concentric and eccentric torques of each muscle group, again the results were not statistically significant. The peak torques were also compared between groups as hamstrings/quadriceps ratios but found to be not significantly different. However, the mean concentric hamstrings/quadriceps ratio of the group with PFPS was found to be 1.02, which is outside of the range of values reported in the literature.