The outside of my left leg was feeling sore, going down to the knee. It almost felt like the time when I had a little bit of trouble with my iliotibial band. I wasn't taking any chances so resorted to the gym bike again. Not ideal but more ideal than getting proper injured. I ain't getting any younger and I am being reasonably aggressive ramping up the hill run mileage. After the hour on the bike my leg felt fine so I think I was just being over cautious.