No Difference In Muscle Excitation Between Runners With And Without Patellofemoral Pain During Prolonged Run

Abstract

PURPOSE: To determine if muscle excitation amplitudes differed from beginning, middle, and end of a prolonged run in runners with and without patellofemoral pain. METHODS: Five recreationally active female runners with history of running with patellofemoral pain (PFP) were matched to five female runners without lower extremity pain (CON) (PFP: age = 21.2+2.68 years, ht = 1.62+0.10m, mass = 67.45+6.10kg; CON: age = 21.2+1.30 years, ht = 1.66+0.12m, mass = 67.45+7.26kg). Wireless EMG surface electrodes were placed bilaterally on the rectus femoris (RF), vastus medialis oblique (VMO), biceps femoris (BF), and gluteus medius (GMED). EMG data was sampled at 2000Hz. Participants ran at a self-selected pace on a treadmill until they met exertion or pain criteria. EMG signals were passed through a 4th order, zero lag, Butterworth high-pass filter with cut-off at 10Hz, low-pass filter with cut-off at 350Hz, and full wave rectified. Average maximum EMG amplitude for 20 steps from 3 time points (beginning, middle, end) of the run were compared for each group using separate paired samples t-tests for each muscle and group. Alpha level was set at p<0.05. RESULTS: No statistically significant differences were observed in EMG amplitude of any muscle for either group when comparing amplitude between participants’ first, middle and last trial of the run (PFP: Max_RF: 0.136mV, 0.117mV, 0.100mV, p>0.05; Max_VMO: 0.506mV, 0.464mV, 0.519mV, p>0.05; Max_BF: 0.273mV, 0.273mV, 0.274mV, p>0.05; Max_GMED: 0.121mV, 0.101mV, 0.096mV, p>0.05; CON: Max_RF: 0.103mV, 0.068mV, 0.073mV, p>0.05; Max_VMO: 0.051mV, 0.464mV, 0.052mV, p>0.05; Max_BF: 0.146mV, 0.151mV, 0.149mV, p>0.05; Max_GMED: 0.102mV, 0.086mV, 0.078mV, p>0.05). CONCLUSION: Neither groups of runners experienced a significant change in EMG amplitude from beginning, middle and end of a prolonged run. Running with active patellofemoral pain does not appear to change muscle excitation amplitude of the RF, VMO, BF, or GMED during a prolonged run.