Bone stress injuries in triathletes are driven by training-load progression errors and are compounded by Relative Energy Deficiency risk factors — not explained by a fixed mileage threshold
Interpretation
Neidel et al.'s retrospective survey of German elite triathletes found 23% reported at least one stress fracture, with risk factors including female sex, prior competitive sport, vitamin D/iron deficiency, and menstrual disturbance (10 of 17 women reporting menstrual disturbance had also had a fracture). Warden et al.'s review reframes bone stress injury as fundamentally a workload-progression error rather than a fixed-threshold problem — there's no single safe mileage number, only a rate-of-change one. The IOC's REDs consensus statement adds that impaired bone health is one of the best-documented REDs outcomes in both sexes, and that low carbohydrate availability specifically raises bone-resorption markers in male endurance athletes, extending the risk picture into fuelling.
Practical implication
Address bone stress injury risk through load-progression discipline (not just total volume) and fuelling/energy-availability screening together, especially for athletes with menstrual disturbance or a history of restrictive eating. The Neidel data is retrospective and self-reported — treat the specific percentages as directional, not precise population rates.
Sources
3 sources, independently verified.
23% of respondents (20 of 86) reported at least one stress fracture, all lower-limb, 52% in the metatarsals, giving an estimated incidence of 4.8%/year. Identified risk factors were female sex, prior competitive sport, vitamin D/iron deficiency, and menstrual disturbance — notably, 10 of 17 women reporting menstrual disturbance had also had a fracture. A retrospective questionnaire design, so recall and selection bias are real limitations.
Frames bone stress injury fundamentally as a workload-progression error rather than a fixed volume threshold: there is no single 'optimal' workload number, but progressing intensity sensibly and reducing load magnitude (e.g. via cadence changes) after a repeated BSI are the evidence-backed levers. Reinforces that BSI risk is about the rate of loading change, not an absolute mileage ceiling.
IOC consensus statement naming impaired bone health as one of the best-documented outcomes of Relative Energy Deficiency in Sport (REDs) in both women and men, and noting that low carbohydrate availability specifically raises bone-resorption markers in male endurance athletes — extending the bone-stress-injury risk picture beyond training load alone into fuelling and energy availability.