Skeletal health (bone shape/size/density/mass, and joint shape) is an important determinant of mid-life musculo-skeletal diseases including osteoporosis/fractures and osteoarthritis. Factors acting across the lifecourse from in-utero to older age influence skeletal health and our previous research suggests early-life skeletal loading may be important for healthy skeletal development. For example, we have shown that children who reach motor milestones, e.g. walking, jumping, at older ages than average have smaller, weaker bones and different joint shapes even in adolescence and old age. We postulate that this is due to both delayed early-life leg loading and because late walkers tend to be less active throughout life which also affects skeletal health.
Skeletal growth is quickest during the intrauterine period, when the skeleton is first assembled. However, there is little information on how skeletal loading during intrauterine development influences bone health. Objective assessment of fetal movements are difficult, but fetal position – breech or cephalic – will influence movements with these likely to be lower in breech infants as leg movement is constrained. Our research, and that of others supports this, showing that breech-born babies have smaller bones and different hip shape at birth compared to cephalic-born children. However, it is unclear whether these differences continue into later childhood, and whether they are explained by differences in activity post-birth. The aim of this study is to examine skeletal health in breech and cephalic-born children in adolescence, and to what extent any differences are explained by differences in physical activity and body composition between these two.