Warm-ups VS. Stretch

Always warm-up before a workout, even before doing stretches. The two are not one and the same. A 'cold' muscle when stretched will likely tear and could take well over a year to recover. This is something you want to keep in mind, especially during winter. The point of warming up is to prevent injuries and muscle pulls during workouts and to get the blood pumping through your body to improve performance. And apparently, since this isn't obvious: you don't work out with the air conditioner or the fan on.