A proper warm up can increase the blood flow to the working muscle which results in decreased muscle stiffness, less risk of injury and improved performance.
Additional benefits of warming up include physiological and psychological preparation. Recently there has been a shift in thinking and scientific evidence from the ‘traditional’ warm up consisting of a light jog and then 10-15minutes of static ‘long hold ‘stretching after.
Research work by McNair (2000)  and Knudson (2001)  suggests that the use of dynamic stretches - slow controlled movements through the full range of motion - are the most appropriate exercises for the warm up, and by contrast, static stretches are more appropriate for the cool down.
Here are some ideas on how to warm up before your run or game:
1. Gradually increasing the intensity of your specific sport is always a good start. If about to play soccer, rugby or go for a run, begin with a light jog and then add a few faster paced run throughs. Focus on smooth controlled movements with ‘drive’ and not necessarily at full flat out pace.
2. Movements that are specific to your sport. These could include step lunges or running low and zigzag for netball, soccer and rugby. Short 5-10 meter sprints while changing direction, or swinging/pumping movements of the arms while skipping to warm up the upper body. Sprints and dropping down to touch the sidelines. Use your imagination here. Think of all the drills you may practice at training and use them as your ‘calisthenic-like’ warm up to prepare your muscles for your sport.
3. The ‘Skip with a Twist’ exercise. A simple warm up exercise for the muscles of the core, upper body and legs.
Read more at http://sportsmedicine.about.com/od/sampleworkouts/qt/SkipTwist.htm
Cooling down after your game should consist of a light 5 minutes jog or walk to decrease body temperature and remove waste products from the working muscles such as lactic acid. Follow this up with 5 to 10 minutes static stretching exercises. Static stretches are more appropriate to the cool down as they help muscles to relax, realign muscle fibres and re-establish their normal range of movement.
These stretches should be held for approximately 10 - 30 seconds. Stretching after your game not only has benefits in the physiological state of your muscles and joints, but it also just feels great!
1.MCNAIR, P.J. et al. (2000) Stretching at the ankle joint: viscoelastic responses to holds and continuous passive motion. Medicine & Science in Sport and Exercise, 33 (3), p. 354-358
2.KNUDSON, D et al. (2001) Acute Effects of Stretching Are Not Evident in the Kinematics of the Vertical Jump, Journal of Strength & Conditioning Research, 15 (1), p. 98-101