Muscle load: endurance test (MPF)
Muscle fatigue is assessed by Median Power Frequency
(MPF) during a sustaining test for shoulders and forearms,
expressed by differences in muscle conductive velocity and
synchronization of Motor Units (MU) resulting in a shift to
lower frequencies (Eberstein and Beattie, 1986; Bigland-
Ritschie et al., 1981, 1986). The same muscles as for MVC
are subjected to a sub-maximal effort. The endurance tests
included: Forearm muscles: A dynamic muscle contraction
of clenching Wrists from full flexion to full extension over
30 s; Shoulders (M. Trapezius): Holding a weight of 1.5 kg
(3.3 lb) over 30 s with stretched arms in abduction (90).
Both, MVC and MPF were recorded by the ME3000PElectromyography
equipment, and analyzed by the MEGAWIN
software (MEGA Electronics, Finland).