How Does Joint Range of Motion Change After Muscle Fatigue in Healthy Young Adults?

• Grace Chesley, Exercise Science, University of Delaware

• Jocelyn Hafer, Kinesiology and Applied Physiology, University of Delaware

Muscle fatigue is the decrease in a muscle’s ability to produce force or power. Fatigue is a common symptom of prolonged or intense activity and can modify an individual’s gait. Previous research has reported decreases in peak plantar flexion angle, hip range of motion (ROM), and knee ROM in response to muscle fatigue. These changes in gait can lead to a decrease in performance. The change of individual joint ROMs could provide insight into which muscles are most affected by a fatigue protocol. Fatigue is often induced by isokinetic dynamometer, which does not replicate causes of fatigue in daily life. The purpose of this study was to determine how muscle fatigue, in response to 30-minutes of physical activity, affects ankle, knee, and hip ROM during the stance phase of gait in young adults. Ten healthy young adults (25.7±3.8 years) were outfitted with 7 Inertial Measurement Units. Preferred pace was determined by completing 5×10-meter walks overground before starting the treadmill protocol. Fatigue was induced by a fast 30-minute walk on a treadmill with three challenge minutes. At minutes 7, 17, and 27 the incline was increased to 3% for one minute. Participants were asked their fatigue level in their legs (0-10 with 0 being no fatigue) before starting on the treadmill and after the protocol was complete. Participants then completed 5×10-meter walks at their previous preferred pace. A paired samples t-test was used to compare stance ankle, knee, and hip ROM before and after 30-minutes of physical activity. Stance ankle, knee, and hip ROM did not change (p>0.05) after muscle fatigue. Relatively high fitness and walking at a non-challenging pace may have prevented participants from reaching a point of muscle fatigue.