A research published in the Journal of Strength and Conditioning Research found that athletes who added single-leg squats to their routines developed the same amount of strength and speed as athletes who added barbell back squats. The study also found that adding more difficult exercises toward the end of a workout regimen increases muscle growth compared to adding them at the beginning. Here's how to do a single-leg squat: Start by standing with your feet shoulder width apart. Bend your left knee and place it against your chest. Without moving your right foot, lower yourself as far as possible while keeping your hips level with your shoulders. When you reach the bottom of the movement, push up through your left leg to return to the starting position. Repeat this motion on the other side. That's one single-leg squat exercise. The study showed that adding single-leg squats to an existing training program resulted in similar strength and speed improvements as adding barbell back squats. This means that these two exercises can be used interchangeably so long as you work each one once per week. Studies have shown that mixing challenging exercises into your routine helps prevent boredom and ensures that you're working all parts of your body during your workouts. This is especially important if you want to see maximum results from your training program.