Physical fatigue or muscle fatigue is a common problem that affects people
who are vigorously involved in activities that require endurance movements.
It becomes more complicated to measure the fatigue level when the dynamic
motion of the activity is included. Therefore, this paper aims to develop a
wearable device that can be used for monitoring physical fatigue condition
during aerobic exercise. A 10-bit analog to digital converter (ADC) microcontroller
board was used to process the data sensed by Ag/AgCl electrodes
and real-time transmitted to the computer through Bluetooth's technology.
The wearable was attached to the knee and connected to the biopotential
electrodes for sensing the muscle movement and convert it into the electrical
signal. The signal then processed by using the fourth-order Butterworth filter
to filter the low-pass filter frequency and eliminate the noise signal. The
results reveal that the fatigue level increased gradually based on the rating of
perceived exertion (RPE), using 10-point Borg's scale, which is rated by the
subject’s feeling. Both muscle's activities in lower limb rise as speed is
increased, and it was also observed that the rectus femoris is functioning
more than gastrocnemius due to the size of muscle fiber. Furthermore, it
was established that the maximum volumetric contraction (MVC) could be
used as a reference and indicator for measuring the percentage of contraction
in pre-fatigue but not to fatigue induced experiment. However, this wearable
device for EMG is promising to measure the muscle signal in the dynamic
motion of movement. Consequently, this device is beneficial for a coach to
monitor their athlete's level of exhaustion to be not over-exercise, which also
can prevent severe injury.