Before diving headlong into a resistance training workout, it's a good idea to first warm up a bit. Getting your blood pumping, your mind focused, and your muscles prepped is an important step in preventing injury. But, just like workouts themselves, not all warm-ups are created equal.

Stretching has come under fire as of late, with some experts suggesting that it actually increases the risk of injury. Of course, there exists a great deal of research that states otherwise, so let's just say the jury is still out on stretching. However, just about everyone agrees that performing some light cardio and warm-up sets before resistance training are vital to a proper workout. Therefore, in order to properly prepare your body for the difficult workout that's soon to come, your warm-up must incorporate the use of the muscles to be trained.

While a light jog on a treadmill or five to 10 minutes on an elliptical is a pretty good way to accomplish this, an even better way is to perform the Barbell Duck-Under and the Barbell Step-Over.

To do the first of these two warm-up exercises, set a barbell at waist level on the supports of either a squat rack or Smith machine. Stand next to the barbell and then take a long stride beneath it as you duck (hitting your head will not make you any tougher). Stand up on the other side and then reverse the motion back to the starting position. Repeat until you've done about ten reps on each side.

The second warm-up exercise, the Barbell Step-Over, is done with the bar set a little lower (literally, not figuratively) -- just above your knees. Starting again with your hip facing the bar, lift your leg above it and land it on the opposite side. Immediately follow with your other leg. Once both legs are on the opposite side, reverse the motion back to the starting position. Repeat until you've completed about 12 reps on each side.

To warm-up your arms using these same exercises, hold light dumbbells in each hand throughout the movement. It's also a good idea to perform at least one or two warm-up sets of the exercise you are about to do. Use much lighter weight during these warm-up sets than what you typically use during the actual sets.