Bone metabolism in elite male rowers: adaptation to volume-extended training

We examined the effect of 6-month volume-extended training on bone metabolism in elite male rowers. Twelve elite male rowers (20.8±3.0 years; 192.9±4.7 cm; 91.9±5.3 kg; body fat 10.1±2.3%; \(V_{{{\text{O}}_{{\text{2}}}\,{\text{max}}}} \) 6.2±0.5 l min⁻¹) participated in this study. Bone biochemical markers, hormones, bone mineral content (BMC), and bone mineral density (BMD) were assessed before and after training. Average weekly training volume was significantly higher (P<0.05) during the 6 months of heavy training compared to relative rest (11.6±0.4 h week⁻¹ vs. 16.8±0.6 h week⁻¹), while intensity remained the same. At the end of training, only arm BMD was significantly increased by 5.7%. Osteocalcin (16.6%), insulin-like growth factor-1 (IGF-1) (20.2%) and the bioavailability IGF-1 index (17.9%) were significantly increased. Before heavy training, relationships were observed between the whole body BMD and growth hormone (r=0.64; P≤0.02), lumbar spine BMD and 1.25(OH)₂ vitamin D (r=0.69; P≤0.04), arm BMD and testosterone (r=0.59; P≤0.05), and arm BMD and adiponectin (r=0.59; P≤0.05). No relationship was found between BMC or BMD and blood biochemical measures 6 months later (r=0.56; P≥0.05). In addition, osteocalcin was related to IGF-1 (r>0.58; P<0.048) and bioavailability IGF-1 index (r>0.59; P≤0.055) before and after training. In summary, heavy training had a moderately favorable effect on BMD. Bone tissue at specific skeleton sites is sensitive to changes in training volume even in athletes with already high BMD values. Changes in BMD and bone formation may be caused by changes in specific hormones such as IGF-1 and adiponectin in male athletes.