All the Right Moves

You joined a gym and carved out time in your schedule to go a couple of days each week. It's only a matter of time before you're sporting your skinny jeans and a tank again, right? Not so fast, especially if you hurt yourself while working out. According to a recent study conducted by the Centers for Disease Control and Prevention, gym injuries are the second most frequent reason people see their MD (after the common cold). No, it's not because free weights are falling on people's heads. Using improper form while exercising is a recipe for injury, causing everything from sprains and strains to tendinitis and muscle pulls, says Maren Piefer, CSCS, founder of Fitnetic: Athletic Fitness in Boca Raton, Florida. And, of course, nursing some body part you damaged can leave you sidelined for months, seriously hampering your fitness progress.

If you're new to the gym or haven't been in one since tie-dye was in style, Piefer suggests setting up three or more sessions with a trainer who can show you proper form to protect yourself. When working out alone, use a mirror to inspect your positioning in each move. And use our cheat sheet here. We reveal the most frequently occurring mistakes in some of the most common exercises, then tell you how to fix them.

The Exercise: Lunges

The Mistake: Walking while lunging
"Because momentum is going forward, it's easy for the knees to bend beyond the toes as you lunge," Piefer says. This strains your knees and puts a lot of pressure on the quads (thigh muscles), when the hamstrings and glutes (the muscles of your buttocks) are the muscles that should really be doing the work.

The Fix: Start with one foot in front of the other, about two to four feet apart (depending on how long your legs are). Squat straight down and straight up, making sure your body weight is on the heel of the front foot and both knees are bent to 90 degrees at the bottom of the lunge. "For more of a challenge, try lunges walking backward," Piefer suggests. This forces you to push through the front heel instead of the toes and fires up the posterior musculature — those muscles in the backs of your legs.

The Exercise: Push-ups

The Mistake: Improper shoulder position.
Push-ups are a standard for strengthening the upper body, but a lot can go awry if you don't do them correctly, Piefer says. Without proper alignment you can overtax the shoulders (which can lead to a sprain) and stress the lower back.

The Fix: Start on all fours with hands shoulder-width apart and shoulders directly over wrists. Then press up into a plank position so your arms are straight but not locked. Lower and raise your body, making sure to maintain a straight line from shoulders to toes throughout the movement (translation: your booty shouldn't be flying in the air or sagging toward the floor). To keep correct alignment while doing the move, think about bringing your chest to the floor — not your belly, nose or thighs — and keep your abs engaged.