Assessing the Perception of Physical Fatigue Using Mobile Sensing

Experiencing constant physical fatigue represents a sign of frailty among the elderly, a symptom that is characterized by a progressive deterioration of physical and mental capacity. Fatigue assessment is often performed through clinical studies, physical tests, or self-report. We present a method to assess an individual's perception of physical fatigue while conducting a common and frequent activity: walking. Fatigue is estimated by measuring the person's demand for oxygen and heart rate. The approach is based on accelerometer and location data collected from smartphones, thus allowing for the continuous assessment of the perception of physical fatigue under naturalistic conditions. The validation of the approach consisted of two user studies with different controlled populations (i.e., young adults and older adults). Results show a margin of error of 6.81% (7.44 bpm) and 5.45% (5.89 bpm) for both aforementioned groups, respectively, and a classification precision of physical fatigue perception of over 90% when compared with methods based on heart rate (ground truth).