REF-251 · Wilson et al., 2025 · American Journal of Physiology — Regulatory, Integrative and Comparative Physiology, 2025; · Paper · PubMed
The effect of sex on the cardiopulmonary and neuromuscular response to high-intensity interval exercise
Participants
n=20 (10 males + 10 females), age 25 ± 3 yr. Two visits: incremental treadmill test (lactate threshold + VO2peak), then 4 × 3-min running intervals at 90% of the final incremental-test velocity (vVO2peak) with 90-s rest.
Protocol
1
Incremental treadmill test → submaximal (lactate threshold) and maximal (VO2peak) data
2
Visit two: 4 × 3-min intervals at 90% vVO2peak, 90-s rest between intervals
3
Before exercise and after each interval: MVC, quadriceps potentiated twitch (Qtw,pot), voluntary activation (VA)
4
Continuous recording: VO2, VCO2, VE throughout
Key Results
| Metric | Males | Females | Significance |
|---|---|---|---|
| Relative VO2peak | 47.2 ± 6.0 mL/kg/min | 44.4 ± 5.8 mL/kg/min | P = 0.292 (no difference) |
| VO2 and VCO2 response, relative to peak | no sex difference | no sex difference | P ≥ 0.781 |
| VE/VO2 and VE/VCO2, 1st interval | lower | higher | P ≤ 0.034 |
| VE/VCO2, 2nd interval | lower | higher | P = 0.006; sex × time P ≤ 0.046 |
| Reductions in MVC, Qtw,pot, VA during the task | no sex difference | no sex difference | P ≥ 0.150 |
| Qtw,pot reduction post-exercise | −24 ± 9% | −15 ± 8% (smaller loss) | P = 0.044 |
Authors' summary: compared with males, females showed greater hyperpnea (poorer ventilatory efficiency) in the initial intervals but a smaller loss of contractile function after exercise — i.e. greater knee-extensor fatigue resistance in females.
Mechanism
Females: higher VE/VO2 and VE/VCO2 during the first two intervals → more breathing for the same relative metabolic load early on; by the end of exercise their contractile function (Qtw,pot) had dropped less than the males'.
Males: better ventilatory coupling early, but a larger post-exercise drop in potentiated twitch force.
Both sexes: no difference in voluntary activation or in the within-task MVC decline → the sex difference is peripheral (contractile) and ventilatory, not central. The abstract does not explain why; fibre-type or absolute-force explanations are inference, not tested.
Practical Application
10 men and 10 women (25 ± 3 yr; VO2peak 47.2 vs 44.4 mL/kg/min, not different), 4 × 3 min running at 90% vVO2peak with 90 s rest: women breathed less efficiently in the first two intervals (higher VE/VO2 and VE/VCO2, P ≤ 0.034) but lost LESS quadriceps twitch force after the session (−15 ± 8% vs −24 ± 9%, P = 0.044); MVC and voluntary activation fell equally in both sexes — women recovered contractile function better, men worse, after the same relative HIIT.
Inference, not tested: the early ventilatory inefficiency in women argues for a longer or more progressive warm-up / first interval so gas exchange settles before the hard work — the study did not test this.
Inference, not tested: do not assume women need longer recovery after HIIT — here they showed the smaller peripheral fatigue; if anything the men carried more post-session contractile fatigue.
Inference, not tested: for mixed-sex coaching, avoid assuming identical early-interval pacing — the female group's breathing cost was higher in intervals 1-2 even though relative VO2 was the same.
The 90-s recovery was the protocol, not a tested variable — the study says nothing about whether it is "adequate".
Limitations
Small sample (10M + 10F), young adults (25 ± 3 yr) — may not generalize to masters athletes
Treadmill running, not cycling — neuromuscular fatigue profile may differ in cycling (less eccentric component)
Single HIIT format (4 × 3 min) — unclear if sex differences persist across other protocols (30/15, Tabata, etc.)
Menstrual-cycle phase control not described in the abstract
How this entry was checked and changed
Content correction 2026-09-27
Direction reversed: the entry said females had greater knee-extensor fatigue resistance LOSS / greater peripheral fatigue and "may need longer recovery" -> the abstract: females had LESSER reductions in Qtw,pot post-exercise (−15 vs −24%), i.e. greater fatigue resistance; Mechanism and Practical bullets rewritten.
Interval count said 2 × 3 min (Participants) and 3 × 3 min (Protocol) -> 4 × 3 min per the abstract.
"sex × time P ≤ 0.046" was attached to knee-extensor fatigue -> it belongs to the ventilatory (VE/VO2, VE/VCO2) interaction. Sport line "cycling, running, swimming" -> running. Removed the untested "90 s recovery is adequate for males" bullet.