Warm Up before workouts

Many people just start their workout once they enter the gym. I have seen people taking the dumbells when they enter the gym and start on with that. Thats not a good practice and it will not be advised by the coach in the gyms.It is better to warm up your body so that the temperature increases by few degrees.The main purpose of warm-up is to prepare your body for heavy workouts and avoid injuries.Warming up for fifteen minutes is advisable.The warm must also include stretching exercises so that you can avoid the sprain problems.
The warm-up becomes at most necessary when people do train their thighs and back. So free sit ups and pull ups can help you out.Push ups can also help warming up upper half of the body.
So never forget to do these for efficient body building.