"The safest way to use strength machines or dumbbells is: in lifting phase, exhale for two counts and hold briefly at the top of the contraction, then return as you inhale for four counts," says Pillarella. "Always exhale during the hardest part of the work."
7. Giving your abs a free ride. Many people do crunches or abdominal machine workouts without ever toning their abdomens. The problem is that they're using the upper torso, neck, and head to do the work.
"Do mindful exercise," says Pillarella. "The contraction should be from the ribcage to the hip bone. Put your mind into the muscles that are working, and keep all the other muscles quiet."
8. Doing lackluster lat pull-downs. On this machine, you're seated with a bar overhead. Some people stick their heads forward and pull the bar down behind their heads. But doing it this way could injure your spine or neck -- and your back won't get that coveted "V" look.
Instead, "pull the bar down in front of your shoulders and chest, and put your mind into muscle contractions in your back," says Pillarella.
9. Using maladjusted machines. Weight machines are made for people of all shapes and sizes. You must adjust them to fit if you want to get results and avoid injury.
For example, using an improperly set leg-extension machine puts stress on your knees, says Mark Kasper, EdD, a spokesman for the American College of Sports Medicine. "Another problem with improperly adjusted machines is that you don't work your muscles through the full range of motion," he says.
Have a qualified trainer show you the proper settings for your physique, and write them down on a card that you carry to the gym.
11. Bouncing. Bouncing during a stretch can increase your risk of straining or pulling muscles, Pillarella says. Instead, "hold a static stretch with no movement at the joints. Your body should feel lengthened but not to the point of pain."