Don't waste your time (or risk injury) with these moves the pros won't touch 8.Crunches Do: Horizontal Squats Research shows that people who suffer from spine conditions such as spinal stenosis (a narrowing of the vertebral lumen), disc bulging, or herniation should not do crunches," says Linda LaRue, RN, certified personal trainer and creator of the Core Transformer. The horizontal squat may not be a well-known exercise, but "it's a great move that works your entire core three-dimensionally and involves acceleration and deceleration (most sports injuries happen when you're decelerating). You can also progress this move by adding a side plank or mountain climbers at the end," LaRue says. To do the horizontal squat (pictured), start on hands and knees, keeping belly button drawn into spine and holding a constant kegel (the same feeling as holding in urine when you really need to go). Lift knees off ground slowly, shifting weight into legs, sitting back into hips as if doing a squat. Quickly drive body forward, extending legs into the top of a pushup or plank position. Hold this pose for 2 seconds, keeping head stacked in a straight line with hips, knees, and ankles. Keep shoulders down and stacked directly above hands. 9.Double Leg Lifts Do: Bridges "People do leg lifts to tone the abs, but it's actually one of the worst exercises for the lower back," says Lisa Kinder, certified personal trainer and star of the 10-Minute Solution: High-Intensity Interval Training DVD. "When the legs are lifted, one of the prime movers is the psoas, which attaches to the lumbar spine vertebrae. When this muscle is contracted, it pulls the lower back into hyper-extension and squeezes the discs, which can put a person at risk for a herniated disc." Instead, Kinder recommends glute bridges (pictured). "This exercise will lift your booty, tone your thighs, strengthen your back, and sculpt your abs," she says. To do it, lie faceup with knees bent, hip-width apart, and feet flat on the floor. Gently contract abdominal muscles to flatten lower back into the floor (try to maintain this gentle contraction throughout the exercise). Exhale, and keeping abs engaged, lift hips off the floor and lift toes, pressing heels into the floor for added stability. (Avoid pushing hips too high, which can cause hyper-extension in the lower back. Keeping abs strong helps prevent arching.) Inhale as you slowly return to start. 10. Lat Pulldowns Behind Head Do: Kneeling Band Pulldowns Lat pulldowns behind the head force the shoulders to work at an angle they're not designed for, which can cause inflammation and tears in the rotator cuff muscles, says Matthew Richter-Sand, certified personal trainer, sports nutritionist, and owner of NX Fit. The trouble is that [pulling a weighted bar down behind the head] slowly tears the rotator cuff, so it's hard to realize that you're doing damage. Plus, the only way to avoid smashing your head is to extend your head forward, which puts even more stress on your spine. Kneeling band pulldowns are a better option because you can keep your body perfectly aligned without worrying about a bar hitting your head. Plus, the band allows a full range of motion and provides resistance throughout the entire movement. Doing them in a kneeling position increases engagement of the thigh muscles, which may not be as active during a traditional, seated pulldown, Richter-Sand adds. To do the kneeling band pulldowns (pictured), kneel while holding onto ends of a resistance band anchored at a high sturdy point. Hinge forward about 45 degrees from hips, keeping spine naturally straight. Pull band down, pressing shoulder blades down, and bend elbows by sides. Extend arms overhead. 11. Isolated Biceps Curls Do: Plank Rows While biceps curls aren't an unsafe or "bad" exercise, I'd rather do a three-for-one toning move that strengthens your shoulders, core, and arms at once, says Andrea Metcalf, certified personal trainer and author of Naked Fitness. To do plank rows (pictured), begin in plank position, dumbbell under right hand. Brace abs in tight, and row the weight up to the side of ribcage, bending right elbow in by side. Do one full set (10 to 12 reps) and then switch sides, or alternate arms for each row (just be sure to do equal reps on both sides). 12.Upright Rows Do: Dumbbell Front Raises "[Upright rows] can cause inflammation and pain in your shoulder joints," says Tom Holland, an exercise physiologist and author of Beat The Gym. Dumbbell front raises are a better alternative because they do not require internal rotation of the arms under load, a potentially harmful combination, Holland says. To do the dumbbell front raise (pictured), stand with feet hip width, holding dumbbells in front of thighs, palms facing in. Keeping torso steady, raise arms to shoulder height. Hold for 1 count, and then return to start. 13.Weighted Oblique Crunches Do: The 90-Degree Burn Most people do not perform standing, weighted side-to-side crunches with proper posture, so it creates too much strain on the spine and can lead to lower-back injuries, says Kim Truman, certified personal trainer and owner of Kim Truman Fitness. Since the 90-degree burn only uses your body as resistance, you place less stress on your spine while still working your obliques. To do the 90-degree burn (pictured), lie on right side with legs and feet together, upper-body propped up on right elbow. Bend left arm across chest with fingertips lightly touching the floor. Extend legs and feet slightly in front of body, and lift to about a 45-degree angle, keeping hips stacked. Hold at the top of the movement for about 3 seconds, and then slowly lower legs back to the floor. Perform equal reps on both sides. 14.The Scorpion Do: Kneeling Hip Flexor Stretch The scorpion is typically performed during a dynamic warm-up to activate the glutes and open up the hips, but it places a combination of rotational and extension forces on the lumbar spine which can result in serious injury, says Jon-Erik Kawamoto, C.S.C.S., owner of JK Conditioning. The kneeling hip flexor stretch or single-leg hip lift are both better alternatives because they do not place the spine in a harmful position, he says. To do the kneeling hip flexor stretch (large image) place left knee on a mat with right leg forward, forming a 90-degree angle at each knee. Lift body upright and brace abs. Reach left arm forward and hold onto a body, chair, or wall for balance. Contract glutes and shift weight forward into right foot, pressing pelvis forward to stretch front of left hip and thigh. Hold for 5 seconds. Return to the start and repeat on other side. To do the single-leg hip lift (small image), lie faceup with knees bent, feet flat. Hug right knee into chest with both hands, forming a 90-degree angle with leg. Press left foot into the ground to lift hips up, forming a straight line from shoulders to left knee at the top of the lift. Return to start and repeat on other side. 15.45-Degree Leg Presses Do: Bulgarian Split Squats People often use very heavy weights when performing leg presses, which places a lot of force on the knees and hips and can result in injuries, says Pearla Phillips, certified personal trainer and owner of Fit Body Transformations in Epping, NH. "[Bulgarian split squats] not only will give your legs strength and definition, they also engage your core and work your balance at the same time. This is working smarter, not harder, while reaping better results," Phillips says. To do the Bulgarian split squat (pictured), stand with your back to a box or bench that's about three feet away, holding onto the end of a dumbbell (up to 25 pounds, depending on level) with both hands. Place left foot lightly on top of the box or bench behind you. Bend elbows and bring dumbbell to the outside of right ear. Keeping torso steady, slowly lower into a squat. Press back up to standing.