One half of the sprinting coin: The oxygen transport cascade of a 91-year-old female world-record sprinter

: A 91-year-old female set the W90+ world record in the 200m sprint in 2024 surpassing her previous record by 1.13s. This study characterized her cardiorespiratory fitness, skeletal muscle oxidative capacity, fiber type distribution, capillarization, and satellite cells and compared these outcomes, where possible, to published reference data. Cardiorespiratory responses were assessed during a ramp cycling test to exhaustion, and muscle oxidative capacity (mV ̇O₂) was determined using near-infrared spectroscopy during repetitive arterial occlusions. Fiber type distribution, cross-sectional area, capillarization, satellite cell content and localization, and mitochondrial respiratory capacity were analyzed in a vastus lateralis biopsy. Peak oxygen uptake (V ̇O₂peak) was 23ml·kg⁻¹·min⁻¹ at 98W, with a maximal heart rate of 141beats·min⁻¹ and cardiac output of 13.6L·min⁻¹. The mV ̇O₂ recovery rate constant (k) was 1.83min⁻¹. Fiber composition was 57% fast MyHC II fibers (50%IIa, 5%IIa-IIx, 2%IIx), 38% slow MyHC I fibers and 5% hybrid I-IIa fibers. MyHC I fibers were larger, more vascularized and had satellite cells located closer to capillaries (4267±2181μm²; 1.67 individual capillary-to-fiber ratio (C/Fi), 5.58 capillaries×1000μm-1 capillary-to-fiber perimeter exchange index (CFPE), 1.8µm satellite cell-to-capillary distance) than MyHC II fibers (2752±1608μm²; 1.03 C/Fi, 4.00capillaries×1000μm-1 CFPE and 10.4µm, respectively). Mitochondrial O₂ flux was 58 and 68pmol·(s·mg)⁻¹ during coupled and uncoupled respiration, respectively. The athlete's cardiorespiratory and oxidative capacity resembled those of females' in their 50s or younger. Collectively, her large, well-vascularized slow fibers, high proportion of fast fibers, and preserved muscle oxidative capacity likely contributed to her world record performance, illustrating the remarkable plasticity of skeletal muscle even in very advanced age.