Abstract
To test the effects of different modes of exercise on indices of protein catabolism,
eight adult males on a meat-free diet performed single 60-min bouts of concentric
and eccentric cycle ergometer exercise in two 7-day periods. Although the absolute
intensities for the two exercise bouts were similar, V̇O2 averaged 70% and 40% of V̇O2 max for the concentric and eccentric exercise, respectively. Mean heart rate during
the eccentric exercise was 26% lower (P < 0.001) than during concentric exercise, and only for the latter was post-exercise
lactate significantly elevated. The excretion of 3-methylhistidine, creatinine, and
urea in 24 h urine samples was constant over the 2 weeks in which exercise was performed.
Compared to pre-exercise values, the concentrations of 3-methylhistidine, creatinine,
and urea were unchanged in serum samples obtained immediately after and for up to
48 h following eccentric exercise. However, serum urea concentration was elevated
by 18% and 21% (P < 0.05) in samples obtained immediately and 1 h after concentric exercise only. Despite
the fact that the eccentric exercise was associated with delayed muscle soreness,
these results reveal that neither concentric nor eccentric cycling exercise at moderate
intensity had a major influence on indices of protein catabolism.
Key words
eccentric exercise - concentric exercise - protein catabolism - 3-methylhistidine
- creatine - urea