Sex differences in sweating appear only above a high heat-loss requirement, come from sweat gland OUTPUT rather than gland recruitment
And there is no sex difference in skin blood flow
Protocol
n=16: 8 men and 8 women cycled three consecutive 30-min bouts at fixed metabolic heat production per unit body surface area: 200, then 250, then 300 W·m⁻². Fixing the requirement for heat loss removes body-size and work-rate confounds, so any remaining difference is attributable to sex.
Measures: whole-body evaporative heat loss by direct calorimetry, local sweat rate by ventilated capsule, skin blood flow by laser-Doppler, and sweat gland activation by modified iodine paper (back, chest, forearm).
Key Findings
Overall, despite the same requirement for heat loss, women showed significantly smaller increases in evaporative heat loss (EHL) and local sweat rate (LSR) (P ≤ 0.001).
Sex differences were not consistently observed at 200 or 250 W·m⁻²; they became significant in the third bout, at 300 W·m⁻²: EHL 348 ± 13 vs 307 ± 9 W·m⁻² (men vs women); LSR back 1.61 vs 1.20, chest 1.33 vs 1.08, forearm 1.53 vs 1.20 mg·min⁻¹·cm⁻².
At every site, the lower local sweat rate in women was due entirely to lower sweat gland output, not to fewer activated sweat glands.
No sex differences in skin blood flow at any point during exercise.
Practical Application
In 8 men and 8 women cycling at a matched heat-loss requirement, women's evaporative heat loss and sweat rate fell behind only at the highest load (300 W·m⁻²: EHL 307 vs 348 W·m⁻²), entirely through lower output per sweat gland, while skin blood flow never differed — so "women cool through skin blood flow, men through sweating" is not supported here; the sweating gap is per-gland output that surfaces at high heat loads.
Inference, not tested (no performance outcome here): do not pre-emptively derate heat sessions for female athletes. At the lower heat-loss requirements, sex differences were not consistent; the gap appeared at the highest requirement — so hard work in the heat is where the cooling and pacing plan earns its keep.
Inference, not tested: compare like with like before concluding anything about an individual. Part of what looks like a sex difference in the field may be body-size and work-rate differences, which this design (heat production fixed per body surface area) controlled.
Sex is a separate question from cycle phase — for the cycle, see REF-709.
Limitations
n=16 (8 per sex), acute laboratory exposure. Small. Training status and age are not given in the abstract.
Heat production was fixed per body surface area, not as a percentage of VO₂max — the right control for thermoregulatory questions, but it means the two sexes were not matched for relative exercise intensity.
Menstrual cycle phase was not the variable under study here; this entry answers the sex question, not the cycle question.
Single acute session, no performance outcome — thermoeffector physiology only.
How this entry was checked and changed
Why this level
regraded 2026-09-27 from B+: cross-sectional comparison, n=16
Content correction 2026-09-27
Level B+ -> B (cross-sectional comparison, n=16, per rubric).
"No sex differences at 200 or 250 W·m⁻²" -> "not consistently observed"; added the overall lower EHL/LSR increases in women and the abstract's 300 W·m⁻² values.
"Young and non-elite", "unacclimated" removed (not in the abstract); derating and body-size advice labelled as inference; lead ▶ now states the study's finding with numbers.
Sport "general" -> "cycling" (the exercise mode used).