The aim of this 12-month prospective study was to investigate risk factors for stress fractures in a cohort of 53 female and 58 male track and field athletes, aged 17 to 26 years. Total bone mineral content, regional bone density, and soft tissue composition were measured using dual-energy x-ray absorptiometry and anthropometric techniques. Menstrual characteristics, current dietary intake, and training were assessed using questionnaires. A clinical biomechanical assessment was performed by a physical therapist. The incidence of stress fractures during the study was 21.1% with most injuries located in the tibia. Of the risk factors evaluated, none was able to predict the occurrence of stress fractures in men. However, in female athletes, significant risk factors included lower bone density, a history of menstrual disturbance, less lean mass in the lower limb, a discrepancy in leg length, and a lower fat diet. Multiple logistic regression revealed that age of menarche and calf girth were the best independent predictors of stress fractures in women. This bivariate model correctly assigned 80% of the female athletes into their respective stress fracture or nonstress fracture groups. These results suggest that it may be possible to identify female athletes most at risk for this overuse bone injury.

The incidence and distribution of stress fractures were evaluated prospectively over 12 months in 53 female and 58 male competitive track and field athletes (age range, 17 to 26 years). Twenty athletes sustained 26 stress fractures for an overall incidence rate of 21.1%. The incidence was 0.70 for the number of stress fractures per 1000 hours of training. No differences were observed between male and female rates (P > 0.05). Twenty-six stress fractures composed 20% of the 130 musculoskeletal injuries sustained during the study. Although there was no difference in stress fracture incidence among athletes competing in different events (P > 0.05), sprints, hurdles, and jumps were associated with a significantly greater number of foot fractures; middle- and long-distance running were associated with a greater number of long bone and pelvic fractures (P < 0.05). Overall, the most common sites of bone injuries were the tibia with 12 injuries (46%), followed by the navicular with 4 injuries (15%), and the fibula with 3 injuries (12%). The high incidence of stress fractures in our study suggests that risk factors in track and field athletes should be identified.

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It would seem that the development of a stress fracture results from unsuccessful adaptation of bone to a change in its mechanical environment caused by repetitive loading. It involves the physiological processes of microdamage production and remodelling. Whether the initiating factor is microdamage production or activation of remodelling through direct effects of strain is unclear. The remodelling process involves both the removal of bone which has become fatigue damaged or is extraneous to the requirements of the new loading environment, and the addition of new bone in an manner that is best suited to withstand the new mechanical strain. Normally this process is well modulated and does not cause symptoms. If the amount of bone removed is not sufficient to unduly weaken bone structure and the addition of new bone occurs sufficiently rapidly to correct any weakness before failure occurs or to repair microdamage, the process will successfully lead to a bone with appropriate material strength and geometry to withstand the new strain environment. However, if there is imbalance between bone removal and replacement, together with accumulation of microdamage, signs and symptoms of a stress fracture may result. Any factors which influence bone load, bone strength, or remodelling have the potential to result in a stress fracture. Attention should be paid to the identification of these factors in an attempt to prevent this overuse injury in athletes.

Bone remodeling may be involved in the pathogenesis of stress fractures in athletes. We conducted a 12-month prospective study to evaluate bone turnover in 46 female and 49 male track and field athletes aged 17-26 years (mean age 20.3; SD 2.0) 20 of whom developed a stress fracture. Baseline levels of bone turnover were evaluated in all athletes and monthly bone turnover levels were evaluated in a subset consisting of the 20 athletes who sustained a stress fracture and a matched comparison group who did not sustain a stress fracture. Bone formation was assessed using serum osteocalcin (OC) measured by human immunoradiometric assay and bone resorption by urinary excretion of pyridinium cross-links (Pyr and D-Pyr); high performance liquid chromatography and N-telopeptides of type 1 collagen (NTx) using ELISA assay. Athletes who developed stress fractures had similar baseline levels of bone turnover compared with their nonstress fracture counterparts (P > 0.10). Results of serial measurements showed no differences in average levels of Pyr, D-Pyr, or OC in those who developed stress fractures (P = 0.10) compared with the control group. In the athletes with stress fractures, there was also no difference in bone turnover levels prior to or following the onset of bony pain. Our results show that single and multiple measurements of bone turnover are not clinically useful in predicting the likelihood of stress fractures in athletes. Furthermore, there were no consistent temporal changes in bone turnover associated with stress fracture development. However, our results do not negate the possible pathogenetic role of local changes in bone remodeling at stress fracture sites, given the high biological variability of bone turnover markers and the fact that levels of bone turnover reflect the integration of all bone remodeling throughout the skeleton.

The effect of intense physical activity on female reproductive hormones is well recognised'à nd there is evidence that menstrual disturbances associated with hypo-oestrogenism adversely affect bone density especially at the lumbar spine.45 Physical activity can also have a range of effects on male reproductive function depending upon the intensity and duration of the activity and the fitness of the individual.6 In particular, endurance training may be associated with reductions in circulating testosterone levels. Since testosterone has important anabolic roles, alterations in reproductive hormone profiles may have detrimental skeletal consequences similar to those seen in females with menstrual disturbances. The aim of this brief review is to present the limited literature on the relation between bone density and testosterone levels in male endurance athletes. (BrJ Sports Med 1996;30:205-208) There is controversy about the effects of chronic intense exercise on basal testosterone levels. Some cross sectional studies have found reductions of total testosterone and measures 205 on 11 May 2018 by guest. Protected by copyright.

In recent years responsibility for the administration of schools internationally has shifted from education departments towards self‐governing schools. This trend has resulted in major changes to the role of school principals. Such changes in role may impact on the psychological and physical health of principals, but there has been very little research into this population. A survey of the health and wellbeing of a representative sample of 50 principals of State primary schools in Victoria, Australia is reported. Subjects completed questionnaires measuring health‐related behaviour and stress and arousal levels and participated in comprehensive health appraisals. Principals reported better smoking patterns than the population as a whole. Despite a higher socioeconomic status than the population as a whole, the health status of the principals was not apparently better. Principals reported higher stress levels and worse physical health than a group of white‐collar employees of similar socioeconomic status.