LOSS OF MUSCLE OXIDATIVE CAPACITY AFTER AN EXTREME ENDURANCE RUN - THE PARIS-DAKAR FOOT-RACE

We measured changes in maximal oxygen uptake capacity (VO(2)max), vent ilation, heart rate, plasma lactate and speed at the end of an increme ntal exercise test as a consequence of a relay foot race from Paris to Dakar in 6 subjects. Additionally, anthropometric measurements were t aken and muscle biopsies from M. vastus lateralis were obtained before and after the race. The latter were analyzed with morphometric method s for fiber size, capillarity and muscle ultrastructural composition. Weight specific VO(2)max was significantly reduced from 62.4 to 60.5 m l/min kg after the race while absolute VO(2)max and the other enduranc e related functional variables remained unchanged, Body fat, thigh cro ss-sectional area and thigh volume showed tendential reduction immedia tely after the race but regained pre-race values within a few days. Fi ber size and capillarity were not affected by the race. Volume density of total mitochondria was significantly reduced from 6.98 to 4.89 % o f fiber volume. Both subsarcolemmal and interfibrillar mitochondria we re significantly reduced by 59 and 21 %, respectively. The volume dens ity of satellite cell was increased about three-fold whereas the conte nt of lipofuscin remained constant. It is concluded that extreme endur ance events such as a multi-stage relay race may induce a considerable loss of oxidative capacity of skeletal muscle tissue.