The physiology, the barriers, and the blueprint for a women's sub-4 minute mile.
A viewpoint paper that sparked 10 commentary letters from researchers worldwide — the most active scientific discussion on women's middle-distance running in a decade.
Osborne, Kirby, Black, Vanhatalo & Jones — Journal of Applied Physiology, 2025
The women's mile world record stands at 4:07.64, set by Faith Kipyegon in Monaco in 2023. That's 7.65 seconds from four minutes. The question isn't whether it can happen — it's what the physiology demands.
The number of women who have run under 4:00 for 1,500m has more than doubled in the last five years compared to the preceding decade. The depth is accelerating.
Women have had just over five decades to specialize at this distance — 1,500m was only added to the Olympics in 1972. Based on historical progression rates, the first sub-4 mile is projected between 2030 and 2065.
Estimated VO₂max (mL·kg⁻¹·min⁻¹) required to run 3:59 for the mile. The oxygen demand at race pace is ~81 mL·kg⁻¹·min⁻¹ — necessarily supramaximal.
Target VO₂ kinetics time constant (τ). Faster kinetics means the athlete reaches peak aerobic energy supply sooner, sparing finite anaerobic capacity for the finish.
Aerobic energy contribution for the ideal athlete profile. Only ~15% of the energy would come from substrate-level phosphorylation — maximizing mitochondrial respiration is critical.
VO₂max of 75, τ of 15s. O₂ deficit of only 2.5L. Energy split: 85% aerobic, 15% anaerobic. This athlete can sustain pace with less reliance on glycolysis.
VO₂max of 65, τ of 24s. O₂ deficit of 5.3L. Energy split: 67% aerobic, 33% anaerobic. This falls outside the range reported for successful mile performances.
The mile race time is governed by two parameters: Critical Speed (CS) — the sustainable rate of mitochondrial energy transfer — and D′ — the finite distance capacity from substrate-level phosphorylation. Together, they set the ceiling.
| Time | CS (m/s) | D′ (m) | D′/CS (s) |
|---|---|---|---|
| 3:59.6 | 5.63 | 260 | 46.2 |
| 3:59.7 | 5.67 | 250 | 44.1 |
| 3:59.8 | 5.71 | 240 | 42.0 |
| 3:59.8 | 5.75 | 230 | 40.0 |
| 3:59.9 | 5.79 | 220 | 38.0 |
| 3:59.6 | 5.84 | 210 | 36.0 |
A 5% increase in CS improves performance by 11.4 seconds. A 5% increase in D′ improves it by only 2.0 seconds. Aerobic capacity is the bigger lever.
Kipyegon was only paced for 56% of her world record mile. Drafting behind pacemakers could save 3–4 seconds. Air resistance at 4-min pace increases VO₂ by 5–10%, greatly attenuated by drafting.
Modern carbon-plate spikes with resilient cushioning have fueled the surge of women running under 4:00 for 1,500m. Athlete- and event-specific shoe optimization for 1,609m at 6.71 m/s could save further time.
Mid-to-high altitude training promotes red blood cell production, enhancing blood O₂ carrying capacity and VO₂max — directly increasing Critical Speed.
Caffeine, nitrate, beta-alanine, sodium bicarbonate, and creatine are recommended for middle-distance athletes. Bicarbonate in particular may buffer the acidosis from high-rate glycolysis.
Race-pace efforts during warm-up can speed VO₂ kinetics, maximizing aerobic energy contribution and sparing D′ for the closing 400m. Optimal pacing has <1% coefficient of variation between laps.
Pregnancy increases blood volume, hemoglobin mass, and cardiac output — adaptations that mimic endurance training. The first sub-4 miler might be a mother.
The viewpoint prompted 10 invited commentaries from researchers across the world, each highlighting a different dimension of the challenge. Osborne et al. synthesized the responses in a "Last Word" reply.
Several commentators noted that some current athletes already possess a Critical Speed in the required range — it's the anaerobic capacity (D′) that's insufficient. Increasing lean muscle mass through strength and plyometric training without reducing CS or power-to-weight ratio is a key pathway.
Kipyegon was only paced for half her record mile and barely drafted. Full-race pacing with personalized aerodynamic apparel could save 3–4 seconds — nearly half the current gap.
The explosion of sub-4:00 women's 1,500m performances in the last 5 years coincides with advanced carbon-plate spike technology. Individual shoe optimization for 1,609m at 6.71 m/s offers further gains.
Sodium bicarbonate supplementation — both acutely and as a chronic training adjunct — could extend the anaerobic tolerance window, particularly valuable in the final 400m.
The barrier is physiological, not biological. And the gap is closing.
Women have changed the narrative of what was possible in elite sport. The sub-4 minute mile isn't a question of if — it's a question of when the right combination of physiology, technology, strategy, and support converges. The science says it can happen within a decade.
Read the viewpoint ↗Osborne RJ, Kirby BS, Black MI, Vanhatalo A, Jones AM. Seven (.65) seconds away: the possibility and physiology of a women's sub-4 min mile. J Appl Physiol 138: 1335–1340, 2025. doi:10.1152/japplphysiol.00074.2025
Osborne RJ, Kirby BS, Black MI, Vanhatalo A, Jones AM. Last Word on Viewpoint: Seven (.65) seconds away: the possibility and physiology of a women's sub-4 min mile. J Appl Physiol 139: 263–264, 2025. doi:10.1152/japplphysiol.00521.2025