Surface electromyography (sEMG) and mechanomyography (MMG) are well-studied signals that can reveal information about the physiological behavior of muscles during contraction. The purpose of this study was to quantify, characterize, and analyze the electrical and mechanical muscle responses to submaximal, isometric contractions in the rectus femoris in adults. Previous studies have investigated the use of EMG to monitor muscle fatigue. However, more information appears to be needed about the use of MMG to measure muscle fatigue during submaximal isometric contraction in the rectus femoris. In this study, the utility of MMG as a measure of muscle fatigue or muscle state was investigated. After studying 10 adult subjects (6 females, 4 males) during 2 consecutive fatiguing isometric contractions at 50% MVIC, there was a total sample of 20 contractions. The RMS, frequency, and electromechanical efficiency (EME) were calculated as an average over 2s samples at the beginning, middle and end of the fatiguing contraction for both EMG and MMG. Electrical efficiency and contraction duration were also measured. EMG RMS. MMG RMS, and electrical efficiency showed significant increasing trends during fatiguing exercise (p=0.0001 and p=0.005 respectively). EMG frequency had a significant decreasing trend (p=0.0016). There was also a significant decrease in the contraction duration when fatiguing exercises were repeated in the same session (p=0.0228). EME and MMG frequency did not have significant trends. However, further studies of these parameters during different fatiguing exercises may help expand their utility in monitoring muscle state. Overall, this study suggests that sEMG and MMG may have utility in monitoring muscle fatigue in submaximal, isometric contractions in the rectus femoris. sEMG and MMG may also find future applications in monitoring patients with muscle conditions.

Thesis Completion




Thesis Chair

Mansy, Hansen


Bachelor of Science (B.S.)


College of Engineering and Computer Science

Degree Program

Mechanical Engineering



Access Status

Open Access

Release Date