90 minutes is a lot of cardio. If you had been doing cardio all along and had worked up to 90 mins - that would be fine, but it sounds like you have just started? That is a recipe for injury. It's one thing to be a little sore the next day, but it sounds like you are in actual pain the next day.
Start smaller - do 30 mins everyday and work your way up. You don't want to injure yourself, b/c that will really put a kink in the exercising.
"I'd rather waltz than just walk through the forrest"
- Sprint Triathlon: 9/11/2011
- Half Marathon: 9/18/2011
- Weigh under 210: GOAL!!! As of 7/16/2010
- Next goal: Get BACK to under 210