Purpose: Strenuous endurance exercise increases biochemical markers of bone resorption but not formation, although the effect of recovery duration between consecutive bouts of exercise is unknown. We examined the effect of recovery duration on the bone metabolic response to two bouts of running.
Methods: Ten physically active men completed two 9-d trials. On days 4 and 5 (D4 and D5), participants completed two 60-min bouts of running at 65% V˙O2max separated by either a 23-h (LONG) or a 3-h (SHORT) recovery period. Osteoprotegerin (OPG), parathyroid hormone (PTH), albumin-adjusted calcium (ACa), and phosphate (PO4) were measured from blood samples obtained before and for 3 h after exercise and on four follow-up days (D6-D9). Markers of bone resorption (C-terminal telopeptide region of collagen type 1) and bone formation (N-terminal propeptides of procollagen type 1 and bone alkaline phosphatase) were measured in early morning fasted samples on D4-D9.
Results: There were no significant changes in C-terminal telopeptide region of collagen type 1, N-terminal propeptides of procollagen type 1, or bone alkaline phosphatase with either protocol. OPG, PTH, ACa, and PO4 concentrations increased with all exercise bouts, but the response to the second bout was not altered by recovery duration.
Conclusions: Two 60-min bouts of running at 65% V˙O2max separated by either 23 or 3 h had no effect on the markers of bone resorption or formation from 1 to 4 d after exercise. Reducing recovery duration from 23 to 3 h between two bouts of running did not alter the increase in OPG, PTH, ACa, and PO4 to the second bout.