I exercise pretty often, usually lifting on my Bowflex 3 times a week & doing 30 minutes on my eliptical machine 4-6 time a week. Unfortunately, a part on my eliptical broke last week, and I had to order another. Not wanting to just stop my cardio while I waited for it to come in, I decided to jog a mile after lifting on Sunday morning. It was a mistake. I didn't push myself too hard. I was barely sweating when I was done, but the muscles on the front of my thighs were killing me. I guess that they don't get worked like the others in my normal workout. I streached, and figured oh well, part of getting older. Unfortunately, as the day went on, the soreness got worse. I woke up Monday morning almost unable to get out of bed I was so sore. Walking down my stairs was agony. Here we are Wednesday, and it still hurts, LOL. I think that I've learned my lesson to stick with what I'm used to. Thankfully, my replacement part came via FedEX today!