Running and aerobics are bone-strengthening activities that Lea may incorporate in her current plan. However, the kind of bone-strengthening activities that should be done depends on the stage of development. For children, adolescents and young adults, vigorous activities may be done because it is the stage for building strong bones. On the other hand, adults aged 35 onwards have the tendency to have brittle bones or natural bone loss, therefore, vigorous activities must be lessened in frequency.