Very good, I think. Would have been about 43 when he took office, only a few years after leading the Rough Riders, and was known to engage in the most strenuous activities he could at every opportunity.
AFTER his presidency he was still strong enough to go on an extended African safari, get shot and continue giving his speech, and lead an absolutely epic expedition down an uncharted river in Brazil with his son Kermit. (River of Doubt is a great book about this)
His health didn't start declining until after this trip, due to an infection from a leg wound, worsened by the bullet that was still in his chest (removing bullets is for pansies, dontcha know).
So yeah, early in his presidency he was probably strong enough to punch bears for fun.
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