By:   Sandra Gordon

Squeezing in several workouts a week may make you feel virtuous and on track with your fitness goals, but before you take a fitter-than-thou attitude, check your form. For the most effective work-out, it's quality, not just quantity that counts. If you aren't paying attention, you could be compromising the effectiveness and safety of your fitness routine.

Exercise can be good for your body for all kinds of reasons, but if executed with sloppy style, it’s little more than a waste of time, according to fitness expert Edward J. Jackowski, author of Hold it! You’re Exercising Wrong. “Without proper form, you don't give your body the chance to change positively,” Jackowski says. “You could even harm it.”

We've listed some of the most common form faux pas. If you find you've been slipping up yourself, no need to feel guilty—our experts’ simple fixes will get you back on the right foot.

The botched crunch.
The abdominal crunch is safer than the old foot-anchored, full-body sit-up as long as it's executed the right way. But most people put their hands behind their necks and yank, jeopardizing the delicate cervical region of the spine supporting the head.

Form fix: Place your fingertips lightly on your temples with palms facing in. Because you'll have nothing to grab onto, your abdominal muscles will do the work as you slowly curl up, lifting your shoulder blades off the floor.

The knee-deep lunge.
Lunges can be great for building the quadriceps and hamstrings, which stabilize and protect your knees from injury. Getting down so low, though, that your knee (and your body weight) extends past your toes can overstretch and weaken tendons and ligaments.

Form fix: To lunge properly, start with feet shoulder-width apart. With your back straight and eyes looking ahead, step forward with your right foot, bending your right knee until your hips are only slightly higher than your knee. Your knee shouldn't be flexed more than 90 degrees, and you should be able to see your toes when you look down. Push off with the right foot to return to the starting position.

The hyperextended head roll.
This standby is supposed to soothe, stretch and strengthen your neck, but it may actually strain it, says Lynne Leary-Khater, a certified personal trainer based in Boston. Typically, you start with your chin to your chest and make a full circle with your head. Leary-Khater suggests eliminating the head-back position of the roll because it makes the disks in your neck vulnerable to injury.

Form fix:Starting with your chin down, rotate your head until your left ear is lined up with your left shoulder. Then tilt your head so your right ear is over your right shoulder, and bring it back down to the starting position. You’ll end up drawing a semicircle with your chin.