Breaking limits: rapid sea-to-summit ascent of Mount Everest (8,848 m) in 3 days 23 hours following normobaric-hypoxic pre-acclimatization and staged supplemental oxygen in a non-elite athlete

Introduction Traditional ascent of Mount Everest (8,848 m) typically requires 40–50 days of on-mountain acclimatization. Normobaric hypoxia (NH) pre-acclimatization is a practical home-based alternative; however, no peer-reviewed case report has described a sea-to-summit Everest ascent completed in under four days by a non-elite individual without prior on-mountain acclimatization rotations. Methods A 40-year-old male recreational mountaineer (baseline VO2max 40.8 ml·kg−1·min−1; BMI 30.1 kg·m−2) completed an 18-week structured NH pre-acclimatization program comprising 48 nights of hypoxic sleep (~377 h at simulated altitudes of 1,850–5,486 m; FiO2 16.7–10.5%) and 16 hypoxic exercise sessions (34 h at 3,085–6,000 m; FiO2 14.3–9.8%). Hypoxic dose was calculated as Σ[(95/SpO2 − 1) × h × 100]. During the climb, peripheral oxygen saturation (SpO2) and heart rate (HR) were recorded at each camp, and acute mountain sickness (AMS) was assessed using the 2018 Lake Louise Score (LLS). Supplemental oxygen (O2) was initiated at 0.5 L·min−1 at the start of the ascent from Everest Base Camp (EBC, 5,360 m) and titrated to SpO2 and symptoms up to 3.0 L·min−1 during the summit push. Results The program yielded a combined hypoxic exposure of 411 h and a cumulative hypoxic dose of 4,779%·h (sleep 4,353%·h; exercise 426%·h). VO2max increased from 40.8 to 51.0 ml·kg−1·min−1, and body mass decreased from 118.1 to 101.5 kg. The subject departed New York at 00:30 local time (EDT; 10:15 Nepal Standard Time, NST) on 15 May 2025 and reached the summit at 09:22 NST on 19 May 2025, a total sea-to-summit time of 3 days, 23 hours and 7 minutes; the ascent from EBC to the summit took 60 hours and 22 minutes. SpO2 was 75% at Camp 3 (7,100 m; HR 95 bpm) and 70% on arrival at Camp 4 (7,950 m; HR 105 bpm) and at the summit (HR 105 bpm). On descent, SpO2 recovered to 80% at Camp 4 and 85% at Camp 2 (6,750 m; HR 110 bpm), and was 85% on room air on return to EBC (HR 62 bpm). No AMS was diagnosed during the ascent (LLS 0–1 at all ascending checkpoints); mild AMS criteria were met on descent (LLS = 3), resolving by return to EBC. No high-altitude cerebral or pulmonary edema occurred. Discussion To our knowledge, this case documents the fastest recorded sea-to-summit ascent of Mount Everest by a non-professional athlete. The combination of a structured 18-week NH pre-acclimatization program, objective physiological monitoring, and staged supplemental oxygen, together with the absence of severe altitude-related complications, suggests that rapid ascent without traditional on-mountain acclimatization may be feasible in a well-prepared, closely supervised non-elite individual. Controlled prospective studies are required to quantify the relative contributions of hematological, ventilatory, and mitochondrial adaptations induced by high-dose NH exposure.