1. Introduction
Fatigue is defined as a failure to maintain the required or
expected force or power output [1], which has been classified
into mental and physical fatigue [2]. Physical fatigue is
commonly associated with the elevated stress level caused
by a modern life style and also related to exercise-reduced
maximal force-generating capacity ofmuscle [3].As reported,
energy metabolism and reactive free radicals accumulation
are involved in the pathophysiology of fatigue [4, 5]. When
fatigue happens, it will gradually accumulate and eventually
lead to overstrain, endocrine disorders, a weakened immune
system, even organ lesions [6].
5