When I'm teaching group fitness classes and someone joins the class late, I cringe a little. Not because they are late, I'm glad they came no matter what time! I cringe because they missed the warm up. Warming up before you exercise is so important!
A good warm up will gradually increase your heart rate and increase circulation to your muscles, tendons and ligaments. This helps prevent injury. Don't confuse a warm up with stretching. The warm up prepares your body for what is to come. It should be dynamic, that is, not holding a movement like you would when you stretch. Stretching focuses on specifically lengthening your muscles. Your muscles need to be warm before you can stretch optimally so you need to warm up before you stretch!
A warm up can consist of walking, marching or jogging in place and dynamic stretches (i.e. Arm circles). Doing this for 5 - 10 minutes before your workout can help prevent injury by warming up your muscles and making your tendons and ligaments more flexible helping to prevent tears.