A preponderance of evidence from systematic reviews supports the effectiveness of weight-bearing exercises on bone mass accrual, especially during the growing years. However, only one systematic review (limited to randomized controlled trials) examined the role of physical activity (PA) on bone strength. Thus, our systematic review extended the scope of the previous review by including all PA intervention and observational studies, including organized sports participation studies, with child or adolescent bone strength as the main outcome. We also sought to discern the skeletal elements (eg, mass, structure, density) that accompanied significant bone strength changes. Our electronic-database, forward, and reference searches yielded 14 intervention and 23 observational studies that met our inclusion criteria. We used the Effective Public Health Practice Project (EPHPP) tool to assess the quality of studies. Due to heterogeneity across studies, we adopted a narrative synthesis for our analysis and found that bone strength adaptations to PA were related to maturity level, sex, and study quality. Three (of five) weight-bearing PA intervention studies with a strong rating reported significantly greater gains in bone strength for the intervention group (3% to 4%) compared with only three significant (of nine) moderate intervention studies. Changes in bone structure (eg, bone cross-sectional area, cortical thickness, alone or in combination) rather than bone mass most often accompanied significant bone strength outcomes. Prepuberty and peripuberty may be the most opportune time for boys and girls to enhance bone strength through PA, although this finding is tempered by the few available studies in more mature groups. Despite the central role that muscle plays in bones' response to loading, few studies discerned the specific contribution of muscle function (or surrogates) to bone strength. Although not the focus of the current review, this seems an important consideration for future studies.

Ageing workers can be found in almost all occupations. Assessment of fitness to work in these workers is important, as it aims to match their functional capacity (which is reduced compared to younger workers), to the demands of their work (which may remain the same as that for younger workers). This outcome of assessment is influenced by the interaction between functional capacity, state of health, the nature of work, and possibilities for work accommodation. The assessment of functional capacity should include physical, mental and social capacity, as well as assessment of any disability. In addition to clinical or laboratory measurements, several authors have suggested the use of a 'work ability index' for specific occupations as a practical means of selecting the appropriate worker for the job. This index can also be used for monitoring functional capacity. In addition, as for any fitness to work assessment, a good understanding of the nature of the work and the work environment is required, and possibilities for work accommodations considered. While changes in the work environment and working conditions can be made to suit the functional capacity of the ageing worker, the maintenance of functional capacity is another important issue. There is a place for a greater role for disease screening and health promotion for such workers.