Women really do glow rather than sweat, research has shown.
Researchers studied volunteers of both sexes on exercise bikes and found that women took longer to get sweaty.
Participants were split into "trained" and "untrained" groups and asked to pedal non-stop for an hour.
At intervals they had to heighten the pace in spurts of increasing intensity.
Untrained females took longest to work up a sweat, needing a higher body temperature before they started to perspire.
Sweating helps athletes by keeping their bodies cool and increasing stamina.
Study leader Dr Yoshimitsu Inoue, from Osaka International University in Japan, said: "It appears that women are at a disadvantage when they need to sweat a lot during exercise, especially in hot conditions."
Previous research has shown that men produce larger volumes of sweat than women, partly because of the male hormone testosterone, which promotes sweating.
Physical training reduces the core body temperature point, at which the sweating response is activated.
The new research sheds light on why men and women cope differently in heat waves say the researchers.
Dr Inoue believes there may be an evolutionary reason why men and women evolved to sweat differently.
"Women generally have less body fluid than men and may become dehydrated more easily," he said.
"Therefore the lower sweat loss in women may be an adaptation strategy that attaches importance to survival in a hot environment, while the higher sweat rate in men may be a strategy for greater efficiency of action or labour.
"Both men and women can acclimatise themselves better to heat if they exercise regularly," he added.