Men have a distinct advantage over women in physical strength. But a new study from scientists in a couple of cold-weather states discovered something surprising.

In extremely cold weather, female metabolism appears to be more efficient. That makes them more resistant to fatigue than men during prolonged periods of exertion in frigid temperatures.

Scientists at the state universities in Montana and Wisconsin traveled to Alaska to monitor the performance of men and women participating in the Alaska Mountain Wilderness Ski Classic. The competition occurs in the spring.

This isn’t a leisurely romp on a bunny slope. Participants ski 136 to 161 miles in unforgiving terrain. They traverse mountain ranges under Arctic conditions. Even in spring, temperatures drop as low as minus 2 degrees Fahrenheit.

Researchers tracked a group of volunteer participants by giving them water containing harmless but traceable nonradioactive isotopes. By measuring these isotopes in urine, sweat and respiration, an athlete’s energy expenditure can be measured.

The study notes that women were getting more mileage from each calorie.

Some unrelated studies by the military suggest women might also be more fatigue-resistant than men during warm weather ultra-endurance events. But that’s far from settled science.

This doesn’t mean a physically stronger male athlete would be bested by a female participant in an extreme competition like the Alaskan event. Size and strength still give men a clear advantage.

But they might be more fatigued than women at the finish line, even if they reach it first.