Last Wednesday, I had some time so I ran 5k on the treadmill. I felt pretty good so I thought I'd spend a bit of time on the stationary bike. About a minute in my right hamstring kind of cramped up. I reduced the tension and rode my 20 minutes. My hamstring was sore until Saturday. Every time I'd stay seated for a while and get up, i could just feel the tightness. I guess I'm wondering first, what do you think I did, and second, how do I prevent this from happening again? I'm trying to do little bricks like that to hopefully get prepared for a sprint triathlon sometime later in the year. But, if I keep getting hurt then it's not gonna happen. So, what's up with all this?