Bone responds to mechanical loading according to Wolff's Law: bone tissue remodels in response to the forces applied to it. When bones bear significant load, the mechanical strain detected by osteocytes within the bone matrix stimulates osteoblast activity and suppresses osteoclast activity, shifting the remodelling balance toward net bone formation. This is the fundamental mechanism by which progressive resistance training builds and maintains bone density in adults, and it operates independently of hormonal status.
The Evidence from Randomised Trials
A review by Layne and Nelson, published in Medicine and Science in Sports and Exercise, analysed the evidence from randomised controlled trials and found that progressive resistance training consistently increased bone mineral density by 1 to 3 percent over periods of 12 months in post-menopausal women. Compared to the 2 to 5 percent annual bone loss that occurs in the early post-menopausal period without intervention, this represents a meaningful attenuation of net bone loss. The benefits are site-specific: spinal loading exercises benefit vertebral bone density, and hip-loading exercises benefit femoral density.
The Key Training Variables
- Load: the mechanical stimulus requires weight that is genuinely challenging; light resistance does not produce bone adaptation
- Progressive overload: bone adapts to a given load over time; continuing to increase the load over months is required to sustain the benefit
- Site specificity: exercises must load the specific bone sites that need protection; axial loading for the spine, hip hinge patterns for the femoral neck
- Frequency: 2 to 3 sessions per week is sufficient for bone adaptation; daily sessions at the same intensity do not produce greater bone benefit
- Impact: for adults who can tolerate it, adding impact exercise such as jumping to a resistance programme augments the bone formation stimulus beyond what resistance alone achieves
Sources
- Layne, J.E., & Nelson, M.E. (1999). The effects of progressive resistance training on bone density: a review. Medicine and Science in Sports and Exercise, 31(1), 25-30.
- Watson, S.L., et al. (2019). High-intensity resistance and impact training improves bone mineral density and physical function in postmenopausal women with osteopenia and osteoporosis: The LIFTMOR Randomized Controlled Trial. Journal of Bone and Mineral Research, 33(2), 211-220.
- Guadalupe-Grau, A., et al. (2009). Exercise and bone mass in adults. Sports Medicine, 39(6), 439-468.