The question: I always stretch before I run, but recently I was told I shouldn't. Why? I feel stiff and want to loosen up. Am I setting myself up for injury?
The answer: There are different types of stretching. I do dynamic flexibility exercises before my runs to mobilize my chronically tight hips and calves. If you also do dynamic flexibility exercises, you are not setting yourself up for injury and should keep doing them. If you are doing static stretches (my guess is you are, since static stretching tends to be more common) save them until after your run.
With static stretching, you are passively holding positions for a sustained period. With dynamic flexibility exercises, you are actively moving your muscles through their range of motion.
Both static and dynamic flexibility exercises will help you feel looser, but dynamic flexibility exercises lubricate your joints, increase blood flow and generally prime you for motion. Static stretches calm you down, which is perfect postrun.
For example, if you currently do a static standing quad stretch (by pulling your ankle to your bum) replace it with bum kicks, the dynamic version of the same exercise: Walk or jog while kicking your heel to you bum 20 to 30 times.
Or, if you do the standing hamstring stretch (by placing your foot on a stable object and bending forward), replace it with Frankensteins: Stand tall and move forward by kicking your legs straight out in front of you so you stretch your hamstrings and mobilize your hip joint.
Switching your stretching routine might be an adjustment – not to mention you might feel silly doing the dynamic flexibility exercises – but it is worth it. I feel peppier and lighter on my feet since I have retrained myself to save static stretches for after my workout.
Trainer's tip: Try doing dynamic mobility exercises when you're waiting at a red light. Here's how to do hip swings: Stand perpendicular to a stable object like a parking metre, fingers lightly touching it. Swing one leg forward and back 20 times. Try and keep the leg that is swinging straight and your core tight. Swing the leg from your hip, not your knee.