An electromyography-based multi-muscle fatigue model to investigate operational task performance

We developed a multi-muscle fatigue model (MMFM) by incorporating electromyography (EMG)-based amplitude and frequency parameters, the fast-to-slow twitch muscle fiber ratio, a time multiplier to linearize the cumulative effect of time, and a muscle multiplier to standardize the combined effect of the number of muscles being considered. We validated the model by investigating fatigue development patterns of 10 male subjects performing one sustained-till-exhaustion static and two repetitive dynamic tasks (low and high task difficulty levels) using 0.91 kg and 2.72 kg dumbbells. The results indicated that the MMFM was sensitive to fatigue-related neuromuscular changes and predicted shoulder joint fatigue accurately.