I mean.. nobody smiles in the middle of exercise. I thoroughly enjoy working hard and pushing myself on my bike, but it definitely doesn't make me smile. I might smile 3 hours later when I see I broke a few personal records though.
I do? I mean, I don't consider myself an unusual athlete or anything. But if I'm biking or lifting, I almost always have a smile on my face, even while pushing myself. So do other people I know, so I really don't think it's unusual.
Yes, you are basically an 'unusual athlete', at least in this regard. Going along at top speed or riding up a steep hill takes effort and the last thing on most people's minds is their facial expression - so they might assume an expression that allows easy breathing or possibly tense all their facial muscles.
I have to say, I'm kind of surprised at the negative reaction saying smiling while exercising has gotten in this subthread. It really is something a lot of folks do. It's even something that top-tier athletes do on purpose: https://www.cnn.com/2018/02/12/health/smile-running-energy-p...
Even if it isn't something one does without being prompted, frame of mind is such an important part of performance. Anything that can lower perceived effort is worth taking seriously.
