You probably do pull up most of the time subconsciously. Try riding a bike with flat pedals and you soon notice how often you lift your feet off the pedals on the upstroke.
I also feel a lot less powerful on flat pedals and only pushing down. Hardly a scientific test though and could well be psychological.
I'll have to try next time I'm out on my mtb. I do certainly notice it at the lights though, trying to lift my pedal round to the top. Feels like my foot's fallen off or something



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