Background Low areal bone mineral density (aBMD) is prevalent in elite road cyclists due to non-weight-bearing training loads and, at times, low energy availability (EA). Real-world, site-specific skeletal responses to targeted loading during rehabilitation remain insufficiently characterized. Case presentation A 24-year-old WorldTour-level female road cyclist with low aBMD (Z-score ≤ −1.1) initiated a periodized resistance and impact loading program and daily vitamin D (800 IU). Three fasted-morning DXA and venous blood assessments (Oct-2024; Mar-2025; May-2025) were paired with training logs, dual-sided crank data, menstrual tracking, and weighed diet records. Five days after second DXA, a left grade-2 medial collateral ligament knee sprain precluded loading of the injured limb for ∼11 weeks; rehabilitation emphasized heavy unilateral resistance work of the contralateral limb while cycling volume was maintained. Results From baseline to pre-injury, lumbar and bilateral femoral aBMD increased (all ≥least significant change, LSC). During unilateral rehabilitation, only the trained femur accrued further aBMD (total hip +2.8%; neck +3.8%; both ≥LSC), whereas the injured femur was stable/slightly lower (≤LSC). Whole-body BMD rose further; and leg-specific lean mass diverged (+uninjured/−injured). Right-leg pedal dominance (∼52%–54%) was similar in the 2024 and 2025 seasons, making cycling-related asymmetry an unlikely explanation for the March–May divergence. Across the three sampling time points, cortisol, 25-hydroxyvitamin D, thyroid hormones, and sex hormones were within reference ranges. Menstrual bleeding reappeared in late November 2024 but remained irregular; EA before baseline was frequently low, and after baseline it was assessed once and appeared higher, but no temporal trend can be inferred. Conclusion Progressive resistance and impact loading were associated with rapid bilateral aBMD accrual pre-injury, and unilateral high-strain loading during knee rehabilitation after a grade-2 MCL sprain coincided with site-specific increases in femoral aBMD despite preserved cycling volume. These findings highlight rehabilitation periods as practical windows to deliver targeted bone-loading in non-weight-bearing endurance athletes and support the feasibility of brief, targeted bone-loading as an in-season maintenance strategy, while contributions from energetic and reproductive factors cannot be excluded.
Pettersson et al. (2026) studied this question.