COMPARISON OF MUSCLE FORCE, MUSCLE ENDURANCE, AND ELECTROMYOGRAM ACTIVITY DURING AN EXPEDITION AT HIGH-ALTITUDE

Handgrip force (HF), maximal pinch force (MF), muscle endurance (ME), and the median power frequency (MdPF) of the activity shown in the ele ctromyogram (EMG) were studied at various altitudes in eight normal he althy subjects. MF and ME were measured between the index finger and t humb, and all measurements were obtained at altitudes ranging from 610 to 4860 m during an expedition in the Qinghai Plateau in China. With the change in altitude HE ME, and MF showed no significant change. Com pared to the MdPF at 2260 m on ascent, the MdPF at other altitudes sho wed a significant decrease (P<0.01). Thus, we conclude that muscle per formance (HE ME and ME) was not affected by the environment at high al titude. However, MdPF was affected and the mean MdPF at 610 m after th e expedition did not recover to initial values of MdPF. We suggest the se results may have been affected by fatigue and chronic exposure to t he hypobaric hypoxic environment, since the members of the expedition party expressed feelings of sluggishness and fatigue after the expedit ion.