AEROBIC AND ANAEROBIC WORK CAPACITIES AND LEG MUSCLE CHARACTERISTICS IN ELITE ORIENTEERS

Aerobic and anaerobic work capacities, leg muscle structure and metabo lic characteristics of m. vastus lateralis (NT), m. rectus femoris (RG ) and mm. gastrocnemii (NT and RG) were analysed in five male and seve n female elite orienteers from the Swedish National team (NT) and a re ference group (RG) of eight male and 10 female upcoming orienteers, al l in optimal shape at the end of a competitive season. Maximal oxygen uptake was 78.4 ml/kg/min for NT men (range 75-81) and 67.8 ml/kg/min for NT women (range 62-71), for both groups significantly higher (P<0. 001) than for RG. Maximal serum lactate was 13.3 mmol/l for NT men (ra nge 10-17) and 11.7 mmol/l for NT women (range 8.4-14), which did not differ from RG. No significant correlation was found between maximal o xygen uptake and maximal serum lactate. For NT females only maximal ox ygen uptake was significantly related to running economy (P<0.01). Mus cle biopsies showed a high content of type I fibres in m. vastus later alis as well as in m. gastrocnemius mediale. M. vastus lateralis (NT) had a higher proportion of type I fibres, capillaries per fibre as wel l as CS, HAD and LDH 1-2 enzymes compared with m. rectus femoris (RG) (P<0.01-<0.001), the latter muscle showing a more anaerobic profile. N T males and females had a higher metabolic potential in m. gastrocnemi us mediale than RG (P<0.001). Our results reflect an obligate high and narrow range of aerobic and anaerobic work capacities for successful performance in international elite orienteering. It remains to be show n how these laboratory data are related to individual performance in a uthentic orienteering competitions.