Fitness magazines abound with exercises that promise to get you bikini ready or provide you with ripped abs. Still, not all exercises are created equally. In fact, some can increase your risk of injury. So, how can you sift through the hype and get to the exercises that actually work? We’ve collected three common exercises to avoid, and the beneficial movements to replace them with.

1. Crunches

If you’re a regular at the local gym, chances are you’ve seen people laying on the ab mat, curling their spines and squeezing their midsections. Perhaps, you, too, have performed crunches in the hopes of trimming your midsection. But according to Spokane, WA-based personal fitness coach Ben Greenfield, crunches don’t really work and are actually dangerous: "Imagine your spine is a credit card," he says. "In the same way that repeatedly flexing and extending a credit card will eventually lead to wearing out the card, repeatedly performing the crunching motion can put a lifetime of damaging strain on your back."

Healthy substitution: Planks. Planks will engage your abs without stressing your lower back.

To perform planks: Start by lying facedown the ground. Lift your body, placing your weight on your forearms and toes. Make sure your back is flat and your abs are engaged. Hold for 20-60 seconds and repeat for 3-5 sets.

2. Seated Hip Adductor/Abductor Machine.

You’ve likely seen one of these machines, which consist of a chair that’s bolted to a footrest and a weight tower. But like crunches or sit-ups, the hip adductor/abductor machine "can injure your lower back and place excessive compression on the spine," according to Greenfield.

Healthy substitution: Side lunges.This lower body exercise is different from the standard lunge in that it targets the inner and outer thighs as well as the glutes.

To perform side lunges: Stand with your feet shoulder-width apart. Step laterally to your left side, keeping your right foot in place and stretching your groin. Keep your upper body vertical as you sink your rear toward the ground. Return to starting position and repeat on your right side.

3. Leg extension machine.

Another machine often used in the gym is the leg extension. Although it’s popular, it may also make you more prone to knee injury. "[The leg extension machine] relies on a non-functional movement and places more stress than necessary on the back of the kneecap. This can cause problems not only for those with existing knee pain, but also others who are predisposed to such issues," says Greenfield.

Healthy substitution: Step-ups. This functional movement engages more than just the quads.

To perform step-ups: Find a weight bench or plyometric box (an exercise box meant for step-ups or box jumps). Place your right foot on the step, and push through your foot to propel yourself upward. Finish by standing atop the step. Lower yourself with your left foot, and begin again. Exercises like this "activate other muscles in the legs and core, as well as create a better sense of body awareness when learning proper form," Greenfield explains.

A Note on Recovery

For anyone starting (or changing up) an exercise regimen, soreness will come into play. Exercise burns magnesium, a key electrolyte for energy, muscle health, and recovery. Most people are deficient in do not get their recommended daily allowance of magnesium, says Greenfield, who suggests supplementing with magnesium citrate powder mixed with water for quicker muscle recovery.

Ben Greenfield reviewed this article.


Interview with Ben Greenfield, August 2014.