I see people all the time at the gym who just walk in, muscles cold and start heavy lifting. I always wonder, why do they do it? For the muscle to reach peak strength it needs to warm up. When you begin your exercise, most of the small blood vessels within the muscles are closed. After 10 to 12 minutes of total body exercise, blood flow to the skeletal muscles increases to some 70 to 75 percent and the capillaries open. You sell yourself short by not allotting time to properly warm up the body. Another reason why warming up is important is to prevent injuries. It minimizes the chances of pulling or straining a muscle. An injury to a vital muscle could cause a setback that wipes away all the hard work you previously did to get in shape.
I also tend to see people finish a workout and head home skipping their stretch. I get it. Stretching isn't fun or glamorous but it is important to the growth of your muscles. It increases flexibility, it improves circulation, reduces lactic acid build up, and helps you recover after a grueling workout. It only takes 2-5 minutes to complete stretching. Be careful though not to stretch before exercising. Stretching a cold muscle can actually lead to a strained muscle, which could also cause a setback.