MITOCHONDRIA CHANGES IN HUMAN MUSCLE AFTER PROLONGED EXERCISE, ENDURANCE TRAINING AND SELENIUM SUPPLEMENTATION

The functional and structural responses to acute exercise (E) and trai ning, (T) with or without selenium supplementation (Sel), were investi gated in a double-blind study on 24 young male subjects. The Sel or th e placebo were given over 10 weeks of an endurance training programme. Prior to the programme and on its conclusion muscle biopsies were tak en from the vastus lateralis muscle before and after an exhausting tre admill test of maximal endurance capacity (Cap(max)). The muscle sampl es were examined by electron microscopy to make a quantitative analysi s of the mitochondria population in the muscle fibres. The number of m itochondria per area (Q(A)) and the relative surface occupied by the t otal mitochondria profile area (A(A)) were estimated. The mean area pe r mitochondrion ((a) over cap) was obtained by the quotient A(A)/Q(A) The effects of the isolated or combined independent variables T, E and Sel were analysed by nonparametric tests. Training induced significan t increases in both Q(A) (30%, P<0.001) and A(A) (52%, P<0.001), witho ut changing (a) over cap; T + Sel produced a slight rise of A(A) (27%, P<0.001), which resulted in larger (24%, P<0.001) (a) over cap. The E produced an enlargement of (a) over cap resembling swelling. This phe nomenon was also found for the combinations E + T and E + T + Sel, but it was then far more pronounced in E + T. The training effects observ ed are in agreement with previous descriptions. In contrast, the chang es observed after acute exercise seem to indicate a remarkable short-t erm plasticity of muscle mitochondria. The results in Sel would seem t o suggest a dampening effect of the selenium on the mitochondria chang es, both in chronic and acute exercise. The mechanism of this action o n mitochondrial turnover is uncertain, but might be related to a highe r efficiency of the selenium-dependent enzyme glutathione peroxidase.