Musculoskeletal health is dependent on the physiological relationship between muscle and bone. Bone is known to be highly sensitive to mechanical and load-bearing forces, including voluntary forces exerted by skeletal muscle. Therefore, it is not surprising that muscle activity is often correlated with bone strength across all stages of life. Bones that are subjected to dynamic, mechanical forces, such as those generated during resistance and high-impact exercises, have been associated with favourable geometric properties and include increased cortical thickness and periosteal diameter. In contrast, a lack of muscle activity or function severely impairs skeletal development and drives the loss of bone during disease and immobilisation.
The direct influence of muscle activity on the adjacent bone remains incompletely understood, as it is inherently difficult to separate the influence of muscles from the local and systemic effects of load-bearing forces and physical activity. However, some studies have been able to manipulate muscles independently of exercise and have since provided interesting insight on how muscle size and muscle contractions refine bone structure. Muscle size and function have been shown to play crucial roles in maintaining the characteristic shape of the tibia in rodents and humans, while also contributing to the formation of entheses during skeletal development. Additionally, our recent work has also shown that rapid muscle growth in sedentary, adult mice, initiated cortical modelling and altered bone structure. Further studies are still required to fully understand the physiological relevance of rapid changes in muscle size on bone during development, adulthood and ageing.