Background: Moderate- to high-impact exercise improves bone density across the lifespan, but effects on bone microarchitecture are unclear. This systematic review and meta-analysis investigated the effects of impact exercise on bone microarchitecture ranging from childhood to older age.
Methods: Four databases (PubMed, Embase, SportDiscus, Web of Science) were searched for randomised controlled trials comparing the effect of impact exercise with ground reaction forces equal to, or greater than, running, with no exercise. Bone parameters were measured by computed tomography or magnetic resonance imaging at the tibia, radius, lumbar spine and femur. Percentage change in bone parameters was compared between groups using mean differences (MD) and 95% confidence intervals calculated via random effects meta-analyses. Subgroup analyses for children and young adults, adults, postmenopausal women and older men were performed.
Results: Twenty-eight studies (n=2,789) were included in the meta-analysis. Impact exercise significantly improved total volumetric bone mineral density (vBMD) (MD: 0.79%, 95%CI: 0.40-1.19%), trabecular vBMD (0.78%, 0.33-1.23%), trabecular area (1.39%, 0.28-2.49%) and trabecular bone volume fraction (0.72%, 0.18-1.26%) at the distal tibia, and cortical vBMD (0.22%, 0.01-0.43%) at the tibial shaft. Similar trends for improvements in total vBMD and trabecular vBMD and area were observed at the radius. In our subgroup analyses, impact exercise significantly improved total vBMD (0.51%, 0.08-0.93%) and trabecular vBMD (0.82%, 0.20-1.45%) at the distal tibia in postmenopausal women. In children and young adults, a significant exercise effect was observed for total vBMD at the distal tibia (MD: 0.73%, 0-1.46%), and cortical vBMD (1.59%, 0.84-2.35%) and cortical area (5.12%, 1.55-8.69%) at the radial shaft. Impact exercise had no effect on bone parameters at the lumbar spine or femur.
Conclusions: Impact exercise influences cortical and trabecular compartments differently across the lifespan. Methodological inconsistencies among relatively low number of trials utilising three-dimensional skeletal imaging techniques emphasises the need for additional trials.