Effects of 3 months of non-weight-bearing cycle ergometric exercise on bone metabolism

We evaluated the effect of non-weight-bearing exercise on bone metabolism by measuring serum levels of biochemical markers, N-terminal osteocalcin (OC), and intact OC. N-terminal assay using the radioimmunoassay (RIA) method is considered to be a marker of bone turnover. Intact OC was measured as a marker of bone formation by the sandwich enzyme-linked immunosorbent assay (ELISA) method. As is commonly known, the cycle ergometer is a very popular and useful tool for aerobic exercise used world wide to improve health. In this study, we evaluated the effect of such common exercise on N-terminal OC and intact OC using a cycle ergometer. N-terminal OC was not significantly changed after 30min of aerobic training with a cycle ergometer three times a week for 3 months, whereas intact OC decreased significantly. No changes in bone mineral density of weight-bearing or non-weight-bearing bones were found. These results suggest that the type and duration of exercise using the current training method were insufficient to produce a favorable effect on bone. The current training method consisted of aerobic, non-weight-bearing exercise alone using a cycle ergometer. It is unknown whether the non-weightbearing form of exercise was responsible for our results, or whether the aerobic exercise itself was insufficient. The 3-month period may have been insufficient to stimulate osteogenesis, and it is possible that an exercise period of this duration may instead result in a tendency to suppress bone formation. At any rate, we believe it is significant that we were able to demonstrate, on the basis of changes in bone metabolism markers and bone mineral density, that the nature of this exercise was insufficient to stimulate osteogenesis.