Median Frequency Shift of EMG During Prolonged Load Carriage

Document Type

Student Presentation

Presentation Date



College of Health Sciences


Department of Kinesiology

Faculty Sponsor

Dr. Tyler Brown


Musculoskeletal injuries can result from muscular fatigue common during military training. It is currently unknown how carrying military-relevant heavy body borne loads fatigue lower limb muscles during prolonged walking. Four (3 male, 1 female) participants had activation of eight dominant lower limb muscles (Tibialis Anterior, Lateral Gastrocnemius, Rectus Femoris, Vastus Lateralis, Lateral Hamstring, Gluteus Medius, Rectus Abdominis, Erector Spinae) quantified when walking at 3.0m/s for 60 minutes with three body borne loads (0, 15, and 30 kg). At minute 0, 30, and 60 of the walking task, activation of each muscle was recorded with electromyography (EMG), and median frequency shift (MFS) of the signal calculated with custom Matlab code. Then, MFS for each muscle was submitted to a RM ANOVA to test the main and interaction effects of time (0, 30, and 60 minutes) and load (0, 15, 30kg), with alpha p<0.05. The addition of load reduced MFS for the lateral gastrocnemius (p=0.031), but had no significant effect on any other muscle (p>0.05). Time had no significant effect on MFS for any muscle (p>0.05). With a larger sample, we hypothesize both load and time will impact MFS of lower limb muscles, particularly those responsible for forward propulsion and weight acceptance.

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