Performing at extreme altitude: muscle cellular and subcellular adaptations.

This review reports on the collaborative efforts of the Department of Physiology of the University of Geneva headed by Paolo Cerretelli, the Research Institute at the Federal School of Physical Education in Magglingen and the Department of Anatomy of the University of Bern to elucidate the functional and structural conditions for and consequences of climbing successfully at altitudes in excess of 8000 m. Using a combination of physiological whole body measurements with biochemical, histochemical and morphometric analyses of muscle biopsy samples we were able to establish specific phenotypical alterations of muscle tissue exposed to extreme hypoxia and stress for prolonged periods of time. The decline in aerobic work capacity could be shown to be a consequence of a loss of muscle mass as well as of muscle tissue oxidative capacity whereby muscle capillarity was found to be maintained. The degradation of muscle tissue was further characterized by an increase in muscle lipofuscin. The latter is believed to be the consequence of lipid peroxidation eventually related to mitochondrial loss. Current work ensuing from our long-term collaboration suggests that Sherpas might be protected against the damaging effect of hypoxia by antioxidant mechanisms protecting their muscles under the conditions of extreme altitude.