Abstract
While bones and muscles adapt to mechanical loading, it appears that very specific
types of stimuli must be applied to achieve osteogenesis. Our study assessed musculoskeletal
outcomes to 30 training sessions on an Inertial Exercise Trainer (Newnan, GA). Subjects
(n=13) performed workouts with their left leg, while their right served as an untreated
control. Workouts entailed three 60-s sets each of knee extension, hip extension and
calf press exercises, separated by 90-s rests. Before and after the 30 training sessions,
subjects underwent strength tests (knee and ankle extensors of both legs), DEXA scans
(hip, knee and ankles of both legs), and blood draws. After 30 training sessions 2×2
ANOVAs showed left leg peak torques rose significantly. 2×2 ANCOVAs, with bone scan
area as a covariate, showed significant left leg calcaneal bone mineral content (+29%)
and density (+33%) increases after 30 training sessions. A significant decline in
C-terminal telopeptides of type I collagen, a blood marker of bone resorption, also
occurred after 30 training sessions. The Inertial Exercise Trainer’s large volume
of training session repetitions elicited high peak force, peak acceleration and impulses
that likely provided a mechanical loading stimulus that evoked calcaneal accretion.
Key words
calcaneus - strength - mechanical loading