For a long time, conventional wisdom held that stretching should be performed before your workout, as a means to loosen up the muscles.
The theory behind it being that tight muscles would prevent athletes from being able to perform at peak levels, and that loose muscles were also less likely to get strained. This is still common practice for many recreational athletes.
However, recent studies, like the one mentioned in this article from last years New York Times, have indicated that stretching prior to exercise can potentially loosen you up too much, thereby actually decreasing performance capabilities while increasing susceptibility to injuries. Go Figure.
Personally, I am not a big fan of stretching before a strength training or cardio session; stretching tends to have a calming effect on me, whereas I want to be amped up before a run or training session. Stretching at the end of a workout when my body temperature is already up and I am more relaxed has usually felt better for me.
On the other hand, stretching can be a means of warming yourself up. Flexibility is a cornerstone of yoga practice–and I am a big advocate of yoga (I do it myself, in fact). If you do like to stretch as a warm up, just be careful not to push your stretches too far at the start. You have to ease in.Like I often tend to point out, there are so many different approaches and it’s up to you to figure out what works best for your body. I know a lot of people who want to just be told what to do without having to think, but I urge you not to take that path!
Pay attention to your body while you are working out and experiment with different approaches to see what feels right. Listen to your body and don’t be afraid to make mistakes; there aren’t always such clear cut distinctions between right and wrong. Case in point–this recent article from the Times suggests that having tight hamstrings could actually be beneficial!
For more information, pick up a copy of my new book, Stretching Your Boundaries.