Effect of carbohydrate feeding on the bone metabolic response to running

PURPOSE: Bone resorption is increased following running, with no change in bone formation. Feeding during exercise might attenuate this increase, preventing associated problems for bone. To investigate the immediate and short-term bone metabolic responses to carbohydrate (CHO) feeding during treadmill running. METHODS: Ten men completed two 7 d trials, once being fed CHO (8% glucose immediately before, every 20 min during and immediately after exercise at a rate of 0.7 gCHO.kg-1BM.h-1) and once placebo (PBO). On day 4 of each trial, participants completed a 120 min treadmill run at 70% VO2max. Blood was taken at baseline (BASE) immediately after exercise (EE), after 60 (R1) and 120 (R2) min of recovery and on 3 follow-up days (FU1-FU3). Markers of bone resorption (beta-CTX) and formation (P1NP) were measured, along with OC, PTH, ACa, PO4, GLP-2, IL-6, insulin, cortisol, leptin and OPG. Area under the curve was calculated in terms of the immediate (BASE, EE, R1 and R2) and short-term (BASE, FU1, FU2 and FU3) responses to exercise. RESULTS: beta-CTX, P1NP and IL-6 responses to exercise were significantly lower in the immediate post-exercise period with CHO feeding (beta-CTX: P=0.028; P1NP: P=0.021; IL-6: P=0.036), although there was no difference in the short-term response (beta-CTX: P=0.856; P1NP: P=0.721; IL-6: P=0.327). No other variable was significantly affected by CHO feeding during exercise. CONCLUSION: CHO feeding during exercise attenuated the beta-CTX and P1NP responses in the hours but not days following exercise, indicating an acute effect of CHO feeding on bone turnover.