Bigelow EMR, et al. - Researchers tested the assumption that wide bones would show a greater negative correlation between whole-bone strength and age compared with narrow bones due to previous work indicating connections between remodeling and external bone size. Using height-adjusted robustness (total area/bone length), cadaveric male radii (n = 37 pairs, 18 to 89 years old) were assessed biomechanically, and samples were sorted into narrow and wide subgroups. The divergent regressions of strength–age implied that narrow radii maintained low strength with aging by increasing external size and mineral content to mechanically offset porosity increases. By contrast, the significant negative strength-age correlation for wide radii implied that changes in outer bone size or mineral content did not offset the deleterious effect of increased porosity further from the centroid. Thus, through various biomechanical mechanisms, the low strength of elderly male radii arose. Consideration of distinct regressions of strength-age (trajectories) may inform clinical choices about how best to treat people to decrease the risk of fracture.