The female runner
Evidence: moderate
A roughly 10–12% sex performance gap holds across distance events, driven mainly by physiology. Women oxidise relatively more fat and resist some forms of fatigue better. Much sports-science advice was built on male subjects and may not transfer cleanly.
Male and female distance runners differ in ways that matter for training and racing, and a lot of standard advice was tested almost entirely on men. The differences are real but often smaller and more individual than popular accounts suggest, so the useful stance is to know where sex genuinely changes the picture and where it does not.
The performance gap
Across distance events from 800 m to the marathon, the best women run about 10 to 12% slower than the best men, and that gap has been stable for decades (Santisteban et al. 2022; Hunter et al. 2023). It is driven mainly by physiology rather than participation or training: men have higher haemoglobin concentration, a larger heart and lower body fat (Santisteban et al. 2022; Hunter et al. 2023).
VO2max and substrate use
Most of the male advantage runs through VO₂max. Higher haemoglobin carries more oxygen, and a larger heart pumps more blood, so men have a higher VO₂max even when it is expressed per kilogram of body mass (Santisteban et al. 2022; Hunter et al. 2023). Lower body fat in men also lifts the per-kilogram figure.
Women oxidise relatively more fat and less carbohydrate at the same intensity (Besson et al. 2022). In theory this spares glycogen, which could help in very long events, though it has not been shown to close the performance gap. Women also tend to resist fatigue better in some sustained and repeated tasks.
Thermoregulation
Women and men differ in how they shed heat, with women relying somewhat less on sweating and more on skin blood flow. The practical effect on race performance is modest and easily swamped by body size, fitness and acclimatisation, so it is rarely the limiting factor it is sometimes made out to be.
The male-default problem
Most of the evidence base is male
Women are heavily under-represented in sport and exercise science research, and many studies are male-only (Cowley et al. 2021). This does not make male-derived findings wrong for women, but it does mean the confidence is lower, and that female-specific questions, such as the menstrual cycle or contraception, are under-studied.
Most core training principles, progressive overload, polarised intensity distribution, the value of strength work, apply to both sexes. The honest caveat is that the precise numbers were usually measured on men, and individual variation within each sex is larger than the average difference between them.
What follows for the female runner
The female-specific topics worth real attention are energy availability and bone, not exotic training tweaks. Low energy availability and RED-S carry particular consequences for women through menstrual and bone health, and iron deficiency is far more common in women than men, affecting up to 60% of female athletes (Pengelly et al. 2024). Those move the needle. Phase-based training prescriptions, by contrast, rest on thin evidence: a hormone-verified systematic review of 19 studies found heterogeneous and often contradictory results, with no consensus on which cycle phase is best for performance (Schlie et al. 2025).