Correcting Chronic Creatine Underdosing in a High-Output Athlete: N=1 Evidence for Rapid Phosphocreatine Re-Activation and Performance Stabilization

 Standard “maintenance” creatine guidance (~0.03 g/kg/day) may be inadequate for high-output athletes performing dense, multi-block training. 

Methods: Prospective N=1, within-person study with stepwise correction of chronic underdosing. Daily creatine monohydrate increased from ~1.7 g/d (historical) → ~6 g/d (stabilized then decayed) → ~12 g/d (initiated Jul 16, 2025). Program, caffeine/supplements, hydration, and periodization were held steady; calories rose modestly but not abruptly. Primary outcomes were explosive-pass rate, completion of 3×5 strength sets at prescribed loads, endurance reps at ~50% 1RM(one-repetition maximum), and 30-min cycling power/heart rate (HR) zone distribution; (heart-rate zones 1-5) secondary outcomes included device-estimated heart rate variability (HRV), 1-min HR recovery, resting HR, and body mass. 
Results: Correcting intake from ~1.7 g/d to ~3.4 g/d (same day) yielded immediate performance gains: endurance reps increased (e.g., squat 100 lb from 12+1 to 15+8), more explosive passes, and strength progression (e.g., squat 175×5×3 → 180×5×3). Cycling improved in parallel (30-min avg power ~125 W → ~138 W; HR time shifted toward Z3/Z4 at similar or lower perceived effort). Subsequent sessions set a 20-min power PR (personal record) (150 W) and higher peak power (~496 W). At ~3.4–6 g/d, outputs gradually regressed under accumulating load, consistent with intake < turnover. Escalation to ~12 g/d produced an acute recovery of strength/cycling performance and sustained stabilization through Aug 7, with device-estimated VO₂max (maximal oxygen uptake) rising to 55 (July 1st), improved HR recovery (≈56 → ≈52 bpm at 1 min), stable/↓ resting HR, and no GI issues or edema. 
Exercise Recording 
> Cardiorespiratory training was logged until July 14, after which no structured cardio sessions were performed. All subsequent intervention phases (6 g/d and 12 g/d creatine) were carried out exclusively alongside resistance exercise and isolated cycling tests. This separation allowed attribution of observed adaptations to creatine dosing rather than cumulative endurance training effects. 
Exercise & Cardio Context 
> No cardio sessions were logged after July 14. Performance improvements observed from July 16 onward therefore reflect resistance training blocks and isolated cycling tests only, without concurrent endurance training. This provides a clean separation between baseline mixed-training days (≤ Jul 14) and the creatine dose-escalation phase (≥ Jul 15). 
Conclusions: In this high-output athlete, the nominal maintenance dose was insufficient; maintaining target outputs required substantially higher daily intake, with a clear dose–response in session quality and cardiovascular responsiveness. Findings support phenotype- and workload-adjusted creatine dosing anchored to objective performance/recovery markers rather than body mass alone. The pattern is consistent with an expanded creatine pool and faster Phosphocreatine (Pcr) resynthesis once metabolic throughput (e.g., AMPK/GLUT4-linked) is adequate. Larger controlled studies are warranted. Future N=1 or small-N studies should explore whether sustained 12 g/day intake accelerates tissue saturation curves in non-responders.