Investigations into Changes in Bone Turnover with Acute, Weight-Bearing Exercise in Healthy, Young Men.

摘要

Introduction/relevance to the Symposium: Lower limb stress fracture injuries (SFx) account for a high number of working days lost during initial UK military training, cause considerable morbidity to recruits and contribute significantly to the high attrition from training. Rationale: Recent evidence from the assessment of circulating biochemical markers suggests that changes in bone turnover, a process in which old bone is removed (bone resorption) and new bone formed in its place might be involved in SFx development. Methods and Results: Blood-borne markers of bone resorption (C-terminal cross-linking telopeptide of type 1 collagen - Beta-CTX) and bone formation (N-terminal propeptides of procollagen type 1 - P1NP) and other bone-associated factors (parathyroid hormone - PTH, calcium, phosphate and osteoprotegerin - OPG) were measured before, during and up to four days after acute bouts of weight-bearing exercise. Investigations examined (i) the effect of training status (TS) on responses to exhaustive exercise; (ii) the effect of recovery duration (23 h vs 3 h; RD) between two bouts of moderate exercise; (iii) the effect of increasing exercise intensity (EI); and (iv) the effects of acute, pre-exercise feeding (PF). Beta-CTX, but not P1NP, was increased for four days following exhaustive exercise, but this response was not affected by TS. In contrast, two bouts of exercise separated by either 23 h or 3 h had no effect on Beta-CTX or P1NP. Beta-CTX but not P1NP was higher in the first hour post-exercise with exercise at the highest exercise intensity. PF suppressed resting Beta-CTX concentrations, although it did not suppress the rise in Beta-CTX with subsequent exercise but, compared with fasting, resulted in a greater increase. OPG was increased with exercise in all four investigations but this increase was not affected by TS, RD, EI or PF. Transient increases in PTH were seen with exercise in all studies.