Load carriage aerobic exercise stimulates a transient rise in biochemical markers of bone formation and resorption.

Exercise can be both anabolic and catabolic for bone tissue. The temporal response of both bone formation and resorption following an acute bout of exercise is not well described. We assayed biochemical markers of bone and calcium metabolism for up to 3 days after military-relevant exercise. In randomized order, male (n=18) and female (n=2) Soldiers (mean±SD; 21.2±4.1 years) performed a 60-minute bout of load carriage (30% body mass; 22.4±3.7 kg) treadmill exercise (EXER) or a resting control trial (REST). Blood samples were collected following provision of a standardized breakfast before (PRE), after (POST) exercise/rest, 1 h, 2 h, and 4 h into recovery. Fasted samples were also collected at 0630 h on EXER and REST and for the next 3 mornings after EXER. Parathyroid hormone and phosphorus were elevated (208% and 128% of PRE, respectively p<0.05), and ionized calcium reduced (88% of PRE, p<0.05) after EXER. N-terminal propeptide of type 1 collagen, was elevated at POST (111% of PRE, p<0.05), and the resorption marker, C-terminal propeptide of type 1 collagen, was elevated at 1 h (153% of PRE, p<0.05). Osteocalcin was higher than PRE at 1 through 4 h post EXER (119-120% of PRE, p<0.05). Sclerostin and Dickkopf-related protein-1 were elevated only at POST (132% and 121% of PRE, respectively, p<0.05) during EXER. Trivial changes in biomarkers during successive recovery days were observed. These results suggest that 60 minutes of load carriage exercise elicits transient increases in bone formation and resorption that return to pre-exercise concentrations within 24 h post-exercise.