Table 2.

Research directions for and the specific problems of Fatigue Detection Systems (FDSs).

Research Direction	Specific Problem	Reference Scheme	Physiological Signal
Signal processing	Multi-component and nonstationary signals	[40]	EMG
Information mining	Low-level muscle fatigue	[41]	EMG
	Local muscle analysis	[42]	EMG
	Stereoscopic visual fatigue	[43]	EEG
Sensor optimization	Multichannel detection	[44,45]	EMG; EEG
	Disposable electrode	[46]	EMG
	Detecting position	[47]	EEG
Function extension	Unloaded muscle effort	[48]	EMG
	Muscle recovery	[49]	EMG