Yes. In order to be ready for an intensive workout, you should perform a thorough warm-up. When your muscles, ligaments and joints are cold, they are prone to injury. A warm-up of 5 to 10 minutes is ideal. You should do gentle cardio on the crosstrainer, rowing machine, skipping rope or just shadow box, do jumping jacks or gentle running (on the spot). If you're using heavy weights and hard exercises, you should also do an additional warm-up set. You can also do a full body warm-up consisting of bench presses (for your chest and triceps), cable pulldowns (for your back and biceps) and leg presses (thighs and calves). Your goal should be 20 repetitions of each. As a whole, your warm-up should stimulate and mobilize your body, but not exhaust it.