Abstract

The effects of eccentric exercise on whole body protein metabolism were compared in five young untrained and five older untrained men (61 +/- 1 yr, VO2max = 34 +/- 2ml/kg/min). They performed 45 min of eccentric exercise on a cycle ergometer at a power output equivalent to 80 VO2max (182 +/- 18 W). Beginning 5 days before exercise and continuing for at least 10 days after exercise, they consumed a eucaloric diet providing 1.5 g/kg/day of protein. Leucine metabolism in the fed state was measured before, immediately after, and 10 days after exercise, with intravenous L-<1-13C>leucine as a tracer). Leucine flux increased 9 immediately after exercise and remained elevated 10 days later, with no effect of age. Leucine oxidation increased 19 immediately after exercise and remained 15 above baseline 10 days after exercise, with no effect of age. In the young men, urinary excretion of 3-methylhistidine per gram ofcreatinine did not increase until 10 days postexercise, but in the older men, it increased 5 days after exercise and remained high through 10 days postexercise, averaging 37 higher than in the young men. These data suggest that eccentric exercise produces a similar increase in whole body protein breakdown in older and young men, but myofibrillar proteolysis may contribute more to whole bodyprotein breakdown in the older group. Verf.-Referat