Stretching is unique to each individual… whether you do or don’t what’s more important is that you WARM UP before any significant exercise! Whether that means just simply shaking the muscles up and going for a short jog/walk before running and sprinting or a full loosen up (even a massage of muscles in question!?).
So WARM UP before ANY activity whether it’s a game or just lifting a heavy bag at home or work! – Dr Gareth
relieves muscles tension
keeps muscles flexible, which can help your posture and balance
lengthens muscles and increases range of motion, which helps lengthen your stride
helps prevent muscle and joint injuries by elongating and relaxing muscles
Flushes lactic acid out of your muscles.
(Dr D. Musnick and M. Pierce, A.T.C. from their book "Conditioning for Outdoor Fitness")
The best way to decide whether or not to stretch is to try out a few different routines (including not stretching) and see what works best for you. When you find one that works for you, stick to what works for you no matter what your neighbor says. You don't need to fix what isn't broken, right? Most importantly, if it does break, if your routine stops working for you, start back at step 1 and try out some other routines until you find one that works.
When to Stretch?
You may think that stretching after you run seems like an obvious good choice. Think again. You are already warmed up, but now your muscles are pumping and it takes them awhile to adjust to the fact that you've stopped running.
You should wait 30-45 minutes after you stop running to do so.
warm up thoroughly first
ease into a stretching routine
only static stretches (slow, rhythmic movement)
pay attention to your breathing (take deep belly breaths)
make stretching a habit
listen to your body
hold your breath
force a stretch
hurry through your routine
Don't forget the Warm Up and Cool Down!
The warm up and cool down should not be optional in your exercise routine.