Studies have shown that people who are aerobically fit do sweat more, and begin sweating more quickly, than people who are less fit, when they are exercising at similar relative intensities.
Relative intensity means a fixed percentage, say 80 percent, of individuals' maximal aerobic power, which is ascertained from a person's oxygen uptake and carbon dioxide production during exercise.
Exercise physiologists compare people who are exercising at the same relative intensity, rather than doing an identical task, because they are trying to understand how the body adapts to training, and what happens to sweating, heart rate, oxygen consumption, etc., as people get close to their physical limits, whatever those limits are.
Fit people get more sweaty, more quickly when they are pushing themselves equally hard with respect to their own physical limits. Other individual differences, including gender (on average, men sweat more than women), also influence sweating.
The argument being that fit people sweat more 'efficiently' but there are many factors that influence this.
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