Not sure if error or just odd design, but while the game advises to "Sleep to recover" from high Soreness levels, simply hitting any of the "Wait X min/hr" buttons reduces Soreness level by 1, regardless of chosen length of wait, i.e. "Wait 5 min" is just as efficient as "Wait 12 hr" in that it'll reduce Soreness by 1... except using the former will allow you to fully recover from level 9 Soreness in just 45 mins, as long as you're willing to click the "Wait 5 min" button enough times.