The other half of the sprinting coin: the neuromuscular profile of a 91-yr-old female world record sprinter

: A 91-yr-old female set the W90+ world record in the 200 m sprint in 2024. We characterized her neuromuscular function, fatigability, denervation markers, and single-fiber contractile properties, and, where possible, compared these outcomes with published reference data. Knee extensor muscle architecture, force, power, fatigability, and motor unit (MU) behavior were assessed in vivo, and a vastus lateralis biopsy was analyzed for single-fiber contractile properties and markers of denervation. Quadriceps cross-sectional area was 36.5 cm2, with fascicle length, pennation angle, and muscle thickness of 6.7 cm, 11.6°, and 1.4 cm, respectively. Knee extensor maximal voluntary isometric contraction (MVIC) torque was 79 Nm, power was 28 W, and power declined by 43% during a 4-min fatiguing task. MU recruitment threshold was 12 ± 11% of MVIC. Single-fiber absolute and specific force were 0.88 ± 0.19 mN and 114 ± 10 kN/m2 for myosin heavy chain (MyHC) I and 0.74 ± 0.23 mN and 171 ± 23 kN/m2 for MyHC IIa fibers. Less than 1% of fibers were positive for the denervation marker neural cell adhesion molecule (NCAM), no fibers expressed embryonic MyHC, and ∼1% of MyHC II fibers expressed neonatal MyHC. In vivo muscle size, force, power, and fatigability were largely within the range for individuals one decade younger. MU behavior was comparable with individuals 20 yr younger. MyHC I fibers produced greater absolute force than reported in untrained young females and females in their eighth decade, whereas MyHC II fiber force was lower because of smaller fiber size. Denervation markers were less prevalent than typically reported at this age. Collectively, these findings illustrate the heterogeneous effects of aging on different features of neuromuscular function, even in an elite older female sprint athlete.NEW & NOTEWORTHY We report in vivo neuromuscular function, single-fiber mechanics, and denervation markers in a 91-yr-old female who holds the W90+ 200 m world record. Despite reduced muscle size, force, and power, as well as pronounced fast-fiber atrophy, markers of denervation were similar to those in young females and single-fiber force in slow fibers was preserved. Together, these data highlight the differential effects of lifelong sprint training and aging on neural versus muscular components of the neuromuscular system.