Seasonal variations of bone metabolism and bone mineral density in collegiate alpine skiers
This study investigated the seasonal variations in bone metabolism, mineral density, and physical characteristics in collegiate alpine skiers. Twelve male subjects (20.6 ± 1.5 years) were evaluated for body composition, body mineral density (BMD), serum levels of osteocalcin (OC), bone alkaline phosphatase (BAP), tartrate-resistant acid phosphatase 5b (TRACP-5b), parathormone, and 25-hydroxyvitamin D (25(OH)D). We also measured the knee extensor and flexor strength, maximal power, and vertical jump. Measurements were conducted in the pre-season period (T1), competitive period (T2), end-of-season period (T3), and resting period (T4). The percentage of body fat significantly increased from T1 to T2 - T4 (p < 0.05), but lean body mass significantly decreased from T1 to T2 - T4 (p < 0.05). Although BMD increased at T2 (0.9 %) and T3 (0.8%), as compared with that at T1 (p < 0.05), BAP and OC decreased at T2 and T3, as compared with that at T1 (p < 0.05). TRACP-5b significantly increased from T1 to T2 (p < 0.05). We concluded that it is important to monitor bone metabolism markers and BMD of male alpine skiers throughout the season.