There's a reason squats are hailed as the king of all lower-body moves: They recruit a ton of big, calorie-burning muscles, like your glutes and quadriceps. But they may not give you a complete lower-body workout. The squat is not an effective way to work your hamstrings, according to a study in the European Journal of Applied Physiology.

Researchers measured how much the hamstrings were activated during the leg press, an exercise that closely mimics the squat but allows for more consistent form than the actual movement. They found that the hamstrings were only 25 percent as active during the exercise as the quadriceps.

"It's a common belief that the stress placed on your legs during multiple-muscle, lower-body movements—like the squat—increases the size and strength of your hamstrings, even if you're not hitting them directly," says study author Brad Schoenfeld, C.S.C.S., Ph.D., and author of The M.A.X. Muscle Plan. "But that's not the case." 

Your hamstrings contract when you bend your knee and lengthen when you bend your hips. To fully recruit them, you need to either dramatically shorten or lengthen the muscle during an exercise, explains Schoenfeld. When performing a squat, however, you bend the knee and the hip at the same time, so the length of the hamstring barely changes, he says.

You probably don’t rely on squats alone to target all the muscles in your lower half. But does your routine adequately hit your hamstrings? If it doesn’t, your quads and glutes have to overcompensate for your hamstrings, says Schoenfeld. This imbalance can increase your risk of pulled muscles and knee, hip, and ankle injuries. 

Schoenfeld recommends performing two sets of hamstring-activating moves for every three sets of squats or lunges you perform. Alternate between hip-dominant exercises like the deadlift and knee-flexion dominant exercises like the Swiss-ball hamstring curl to work the entire muscle.

Deadlift

Swiss-Ball Leg Curl