Exercise is known to have long-term benefits on bone mass, but little is known about
the short-term effects of exercise on bone turnover. The purpose of this study was
to investigate whether acute effects of exercise on bone remodelling c<ould be detected
by measuring blood and urinary markers of bone turnover. We measured biochemical markers
of bone turnover in ten healthy, young men before and up to 32 hours after 30 minutes
of brisk treadmill walking. Blood samples were taken before, immediately after and
at 0.5, 1,8, 24 and 32 hours after the exercise. These were assayed for osteocalcin
and bone specific alkaline phosphatase. Twenty-four hour urine samples were taken
over three days (day before, day of and day after exercise) and measured for pyridinoline
and deoxypyridinoline crosslinks. Crosslink excretion was standardised for total body
bone mineral content (TBBMC) and urinary creatinine. Total body bone mineral density
(and content) and body composition were measured by dual energy X-ray absorptiometry.
No changes in the levels of either osteocalcin or alkaline phosphatase were seen at
amy time point following the exercise. Both urinary crosslinks exhibited an increase
in levels on the day of the exercise and a further significant increase the day after
(pyridinoline 38.7 %, p = 0.05; deoxypyridinoline 42.3 %, p = 0.025; median, corrected
for TBBMC). There were significant negative correlations between the crosslinks, osteocalcin
and body fat percentage. In conclusion, the exercise appears to have stimulated bone
resorption within 32 hours of moderate exercise, but there was no measurable effect
on bone formation after 32 hours. A longer study period may be necessary to detect
changes in bone formation.
Key words
Osteocalcin - pyridinoline crosslinks - exercise
