Moses Itauma’s “Gassed-Out” Collapse: A Physiological Deep-Dive

In his first world-title bout, 21-year-old British heavyweight Moses Itauma faced Croatia’s Filip Hrgovic. After eight rounds, Itauma led on all three judges’ cards but entered the ninth round visibly exhausted. Despite a brief surge, his muscles failed to contract effectively, and with 33 seconds left the referee halted the contest as Itauma’s trainer Ben Davison threw in the towel. Itauma, a 241.7 lb, 6 ft 4 in athlete, was carried out on a stretcher, his body “succumbing to complete exhaustion.”

New York Times

Exercise physiologist Dr Andrew Usher explains that boxing performance depends on two systems: (1) the aerobic capacity of the heart and lungs, which deliver oxygen, and the oxidative capacity of the muscles, which extract and use that oxygen. In heavyweights, large muscle mass creates a substantial oxygen debt. Each explosive contraction consumes oxygen that must be replenished; when the muscle’s ability to extract oxygen lags, performance deteriorates rapidly.

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Usher likens Itauma’s collapse to “bonking” in endurance sports—when glycogen stores deplete and the body can no longer sustain effort. The 60-second rest between rounds becomes critical: insufficient recovery leads to hyperventilation, reduced cerebral oxygenation, and heightened risk of brain trauma. The combination of high adrenaline, cortisol spikes, and limited glycogen replenishment (boxers may only drink water) accelerates the deficit.

New York Times

Usher advocates “supramaximal bike sprints” and targeted punch-bag intervals to boost mitochondrial density and improve muscle oxygen extraction. By training the muscle’s oxidative capacity, fighters can develop a larger oxygen reserve, mitigating the stacking oxygen debt that plagued Itauma. The approach emphasizes both aerobic engine development and muscle-level efficiency, especially for “big guys” whose mass magnifies oxygen demands.

New York Times

Usher stresses that many coaches focus solely on heart-lung conditioning, neglecting the muscle’s role in oxygen utilization. He notes that Itauma entered the ring “wired,” with elevated adrenaline causing rapid glycogen burn before the fight even began. Both point to the need for balanced conditioning that tempers stress-induced energy expenditure.

New York Times

• “That has to be trained much more appropriately than it currently is” — Saturday. For Usher, exercise physiologist and British Boxing Board of Control-licensed coach

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• “For Itauma, that debt is just stacking up and stacking up” — Saturday. For Usher, exercise physiologist and British Boxing Board of Control-licensed coach

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• “There’s been a lot of pressure on that kid,” — Saturday. For Usher, exercise physiologist and British Boxing Board of Control-licensed coach

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• “When you think of energy coming out of the body, you’ve got to think about it two ways,” — Saturday. For Usher, exercise physiologist and British Boxing Board of Control-licensed coach

New York Times

Itauma’s high-profile collapse highlights a gap in heavyweight training: the under-development of muscular oxidative capacity. As boxing increasingly rewards explosive power, fighters who neglect muscle-level oxygen training risk premature fatigue and increased injury risk. Incorporating supramaximal interval work could reshape conditioning protocols, potentially extending careers and improving safety for athletes who, like Itauma, possess exceptional speed and mass.

New York Times