3. Using Bad Form. Don't just do the exercise; do it right, says Fabio Comana, MA, MS, certification and exam development manager for the American Council on Exercise.
Improper exercise technique not only poses a greater risk of injury to muscles and joints, it also wastes your time.
You may be thinking you're strengthening one muscle when in fact you are straining another or stressing a joint. For example, doing bicep curls with your knees hyper-extended and your back muscles shortened could do more harm to your knees and back than good to your arms.
Fitness trainers or floor assistants are on hand at most gyms to assist you with proper form. Use them. Ask for someone to walk you through the equipment, showing you proper technique with machines and free weights.
4. Being Too Social. "Social support is great," says Trese. "Knowing that a familiar face will be there at the same time" can keep you going with your exercise regimen. "But you don't want to make it just a social hour."
When walking on treadmills with a companion, Lockhart suggests agreeing to chat during the warm-up and cool-down, but to stay quiet and commit to pushing yourself for the time in between.
"Work at an intensity that burns significant calories and is too high to carry on a full-blown conversation," Lockhart suggests. When you work out with a friend or friends, set some rules first to be sure everyone stays on track with time, Trese advises. Try doing 8 to 10 exercises in 30 minutes, and resting no longer than a minute between exercises.
5. Getting Stuck in a Rut. Muscles have memory, says Pillarella. They adapt, they adjust -- and our bodies plateau.
"If you always use the same piece of equipment, your body will become adept at that type of exercise," she says.
Instead, mix it up.
"If you always use the treadmill, get on the bike," Lockhart suggests. "If you always work at the same pace, practice doing intervals -- shorter surges to build your upper-end capacity. It'll jog the body's systems -- make your body wake up and have to regroup."
To add intervals, increase incline or speed for short periods during cardio exercise, says Trese. With your strength routine, change the order of the exercises or rotate from machines to free weights.
"With more versatility, your muscles won't be prepared and your body will not automatically know how to respond," Trese says. This will keep things fresh for your mind, too, she says, "making workout routines less boring."
Lockhart advises varying your exercise program every six to eight weeks if you're working out consistently. This is enough time for the body to benefit from the routine without getting complacent.