Among the many quiet costs of athletic ambition, bone loss in young female runners stands as one of the least visible and most consequential. A nutritional scientist at the University of Connecticut has found that collagen peptides — the very protein scaffolding of bone itself — may help restore what intense training and insufficient calories quietly erode. The research, published this summer, turns attention toward premenopausal women at a moment when intervention still has the power to shape decades of skeletal health.