One-year changes in bone mineral density and bone turnover markers in premenopausal amateur runners: a prospective study.

A prospective study was conducted to clarify the 1-year changes in lumbar spine and hip bone mineral density (BMD) and bone turnover markers in premenopausal amateur runners and to determine whether jumping and muscle-strengthening exercises have additive effects on the bone parameters in these runners. Thirty-six premenopausal amateur runners were recruited and were divided into the following two groups: a jumping plus muscle-strengthening exercise group (n =21) and a control group (n =15). All participants continued their running practice for 1 year, and the lumbar spine and total hip BMD and bone turnover markers were monitored. For all participants, the lumbar spine and total hip BMD increased modestly after 1 year (1.31% and 1.54%, respectively) in addition to increases in the bone-specific alkaline phosphatase, osteocalcin, and tartrate-resistant acid phosphatase 5b levels (13.2%-27.8%), indicating mild effects of running activity on bone turnover and BMD at clinically relevant skeletal sites. Jumping plus muscle-strengthening exercises did not significantly influence any bone parameters; however, it was difficult to draw definite conclusions because compliance was poor. These results suggest that long-distance running at the recreational level may be useful in maintaining bone health in premenopausal women.

Evaluation of bone, nutrition, and physical function in Shorinji Kempo athletes.

The objectives of this study were to reveal the proportion of Shorinji Kempo athletes who had suffered fractures related to sports activities, and to evaluate bone mass, bone turnover, nutritional status, and physical function in these athletes. A medical examination was carried out for 16 Shorinji Kempo collegiate athletes. Seven athletes (43.8%) had experienced a sports-related traumatic fracture during Shorinji Kempo practice. Four athletes (25.0%) had a lower speed of sound (% young adult mean < 100%), and five athletes (31.3%) had higher levels of urinary cross-linked N-terminal telopeptides of type 1 collagen (a bone turnover marker) than the age-adjusted standard values. All the athletes had a lower daily calcium intake than the adequate intake, 12 (75.0%) had a lower daily vitamin D intake, and 15 (93.8%) had a lower daily vitamin K intake. Significant positive correlations were found between the vertical jump height, and the daily energy, and protein intakes. Results suggest that fractures are a common injury in Shorinji Kempo athletes, and that some Shorinji Kempo athletes need to improve their bone mass, bone metabolism, and nutritional status in order to strengthen bone and improve physical function.

Electromyographic analysis of the knee during jump landing in male and female athletes.

Many noncontact anterior cruciate ligament (ACL) injuries in female athletes occur at foot strike during jump landing when the knee is extended. This study was undertaken to determine the activation level of the quadriceps and hamstring muscles electromyographically. Fifteen healthy volunteers (eight women and seven men), all of whom were collegiate basketball players, participated in the study. The maximum voluntary contraction (MVC) of the vastus medialis (VM) at a knee flexion angle of 15-45 degrees was significantly higher in women than in men. There was no significant difference in overall mean hamstring activity in men and women over the same knee flexion range. However, when the knee flexion angle was 15 degrees , 20 degrees , and 25 degrees , hamstring activity was significantly lower in female athletes. These results suggest that female athletes have a higher risk of ACL injury during jump landing due to increased anterior tibial translation force with quadriceps muscle activity. Female athletes require greater hamstring activation, and it is suggested that exercising this muscle will increase its activity when the knee is extended, thus preventing ACL injury during actual sport motions.