Walking, jogging, and running are all weight-bearing activities often recommended to improve bone health,but the magnitude of loads (stress) (and the resulting deformations (strain)) imparted on bones from these activities typically ranges from 1.2 to 4.0 times body weight depending on the speed of movement [84].Consequently, the effects of these activities on BMD are mixed, although there are some cross-sectional reports that BMD at the hip, spine, and lower extremities are 5% to 10% greater compared to nonathletic individuals [85–88]. Progressive resistance training (PRT) (also known as weight lifting or strength training) is one activity associated with high compressive and bending forces that can increase BMD as well as muscle mass, size, and strength [89]. Indeed, cross-sectional studies of adolescent [90,91]
and adult weightlifters [92,93], bodybuilders [94] and those engaged in recreational weight training [95,96]
have been reported to have 10% to 33% higher BMD at both appendicular and axial sites than nonlifters. In contrast,
athletes involved in nonweight-bearing activities that incorporate forceful muscular contractions, such as swimming and cycling, do not have greater BMD at clinically relevant sites; indeed hip and spine BMD has been reported to be up to 10% lower in these athletes compared to nonathletes