Last week I was running 400m intervals at 7:00 min/mile pace. I planned on 8-10 intervals but with about 100m left on the 7th one I could feel my left hamstring start to tighten up and hurt. I pushed on for a few more strides to see if it was really getting ready to let go and stopped as it continued to get worse. Discomfort and soreness are a normal part of exercise and getting in shape. Over time you listen to your body and learn the difference between them and pain. Pain is a different beast and it means that you are doing damage; you are injuring yourself; you are going to have to take time off to heal.
I was a little sore the next day, but I was able to run without pain. But last Sunday I did a 10 mile long run and about 4 miles into the hamstring started to get sore. It didn't get worse and since I was in the middle of a loop I really didn't have any choice but to finish the run. So I slowed down and took frequent walk breaks and finished the run without any drama. Last night was my first run since Sunday and I figured that a 4 day break would have given the muscle time to heal. I headed to the track to do some intervals, but after a 1.5 mile warmup the hamstring was sore again and felt like it was going to pull as soon as I tried to run the first interval. I immediately pulled the plug on the intervals and did a leisurely 6 mile run instead.
It's official: I'm injured. Fortunately, not badly, but I won't be able to do any speed work for a week or two. In the meantime I need to do a little rehabilitation to let the muscle heal. No speedwork, lots of stretching, a good massage, cross training, and good nutrition until the muscle is healed. I've pulled muscles several times and I am fortunate that this is pretty mild. I've done a couple that really hurt badly and took a while to heal.
Why did it happen? Speedwork is very stressful on the body and makes you very prone to injury. Unless you really want to get faster, don't do sprints or speedwork. Just run at a comfortable pace that gets your heart rate in the desired training zone for fitness. I also just started a diet to try to cut 20+ pounds by the end of the summer. So, I was pushing my body hard and depriving it of nutrients at the same time. Probably not a good idea. So, until I'm done losing the weight I'm going to eliminate the speedwork and just focus on easier runs to burn calories.