Why did he ask me to the gym?

i go to a boarding school with some day students including him and we do backpacking trips in small groups every year. this year he was in my group, and we talked a bit, mostly competitive ab strength. (me challenging him to a core strength contest, him correcting my form on workouts). today he asked if i want to go to the gym w him. i said no because i prefer to work out outside, and he seemed disappointed. i kinda think in hindsight he was asking me out or something, but im not sure.

leaving this open for all to answer in case any girls have experience w something similar.

Why did he ask me to the gym?
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