Perhaps all that leaping and crashing around on skateboards is good for boys after all. A new study shows that high impact activities such as jumping and skipping -- things that can easily be incorporated into warm-ups before sports and PE classes -- can benefit bone health in adolescents. Although puberty is a time when many switch off vigorous activity, researcher Ben Weeks says 80 per cent of bone mass is acquired in the first 20 years of life and especially around puberty, due to the circulating hormones. This makes it a “window of opportunity” for maximising bone mass.

The study involved 99 youngsters with a mean age of 14 who did a special 10-minute warm-up routine twice a week for eight months. The session included various jumps, lunges and skipping, with gradually increasing complexity and repetitions, designed to apply a bone-stimulating mechanical load on the skeleton. Students worked up to about 300 jumps per session by the end of the study. Compared to other students who did a regular warm up, boys in the study improved whole body bone mass while girls bone mass improved at the hip and spine. The boys also lost significantly more fat than other boys.

Mr Weeks said the different effects for girls and boys reflect their different rates of physical maturing -- most boys in the group were right on puberty while most girls were past it. The improved bone strength in girls at the hip and spine is promising, he points out, as those are typical sites for fractures in the elderly. ~ Science Daily, Sep 1