Missoula [1] is a good place to get some exercise after a long car trip.
The university’s [2] indoor Grizzly Pool (406/243-2763) has regularly scheduled public hours and is a good option for lap swimmers.
An indoor water park at McCormick Park (600 Cregg Ln., 406/721-7275), at the west end of the Orange Street Bridge, has two waterslides and places for both lap swimmers and water play.
Splash Montana, at Playfair (3001 Bancroft, 406/542-9283), behind Sentinel High School, is an outdoor pool with features for both kids and adults.
Links:
[1] http://www.moon.com/destinations/montana/missoula-and-northwestern-montana/missoula
[2] http://www.moon.com/destinations/montana/missoula-and-northwestern-montana/missoula/sights/university-montana