Adaptations of immature trabecular bone to exercise and augmented dietary protein.

Exercise and diet synergistically influence bone, but it remains unclear whether augmenting dietary protein intake during moderate exercise has a beneficial or negative effect on immature bone mechanical integrity. Thus, we examined lumbar vertebral bodies (L6) and femoral necks (FN) in trained and untrained rats fed either a recommended protein (15%) or higher protein (30%) diet. Male Wistar rats (8 wk old) were assigned to one of two exercise groups (high protein exercise [HPE], recommended protein exercise [RPE], run 3 d.wk-1 on a motor-driven treadmill at approximately 80% of their maximum oxygen capacity) or to one of two sedentary caged-control groups (high protein control [HPC], recommended protein control [RPC]. After 8 wk, in the HPE group, FN maximum normal stress was significantly greater than all other groups, and FN maximum load and energy at maximum load (per unit body mass) were significantly greater than the sedentary control groups. L6 stress at the proportional limit and initial-maximum stress did not differ among groups, but L6 percent ash was significantly greater in the HPE and RPC groups. Thus, coupling high dietary protein with moderate exercise can produce positive effects on immature rat femoral neck mechanical properties and structure.