Physical activities undertaken in childhood, particularly activities which apply large forces quickly convey optimal benefits to bone mass, size, and structure. Evidence is accumulating that benefits persist well beyond activity cessation. This review examines the potential for early childhood activity to improve bone mineralization and structure and explores childhood activity as prevention for osteoporosis in later life.

ABSTRACT:Our aim was to assess BMC of the hip over 8 yr in prepubertal children who participated in a 7-mo jumping intervention compared with controls who participated in a stretching program of equal duration. We hypothesized that jumpers would gain more BMC than control subjects. The data reported come from two cohorts of children who participated in separate, but identical, randomized, controlled, school-based impact exercise interventions and reflect those subjects who agreed to long-term follow-up (N ‫ס‬ 57; jumpers ‫ס‬ 33, controls ‫ס‬ 24; 47% of the original participants). BMC was assessed by DXA at baseline, 7 and 19 mo after intervention, and annually thereafter for 5 yr (eight visits over 8 yr). Multilevel random effects models were constructed and used to predict change in BMC from baseline at each measurement occasion. After 7 mo, those children that completed high-impact jumping exercises had 3.6% more BMC at the hip than control subjects whom completed nonimpact stretching activities (p < 0.05) and 1.4% more BMC at the hip after nearly 8 yr (BMC adjusted for change in age, height, weight, and physical activity; p < 0.05). This provides the first evidence of a sustained effect on total hip BMC from short-term high-impact exercise undertaken in early childhood. If the benefits are sustained into young adulthood, effectively increasing peak bone mass, fracture risk in the later years could be reduced.

Given that the Get Up and Go discriminates between fallers and nonfallers and is associated with lower extremity strength and power, fall prevention strategies should focus on improving both functional mobility and lower extremity strength and power.

Four-day school weeks are used in over 1,600 schools across 24 states, but little is known about adoption and implementation of these types of school calendars. Through examinations of school calendars and correspondence with school districts, we have compiled the most complete four-day school week dataset to date. We use this unique database to conduct a comprehensive analysis of four-day school week policy adoption and implementation. We find adoption of four-day school weeks is often financially-motivated and has generally remained a small, rural district phenomenon. These schedules feature a day off once a week – often Friday – with increased time in school on each of the remaining four school days that, on average, is nearly an hour longer than the national average among five-day schools. Four-day school week schedules average only 148 yearly school days, yielding yearly time in school that is below the national average for five-day schools despite the longer school days. Substantial heterogeneity exists in the structure of these schedules across states, which may help explain differential four-day school week effects on student outcomes across institutional settings in the previous literature.

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