Strength training has been and still is primarily sagittal plane and double limb. However, we’ve used single limb training for upper body stuff for years and raved about its effectiveness. We call it dumbbell training. Dumbbell bench presses and incline presses are widely accepted, as are dumbbell rows. However, unilateral lower body training has not been embraced to the same extent. Exercises such as Step-ups and Lunges are very rarely used once people have progressed from beginner status.
The idea that single leg squats or lunges done with only bodyweight might be beneficial to athletes or to those looking to gain more muscle mass will be the focus of this article. Physical training really comes down to two things: anatomy and physics. Our knowledge of physics hasn’t changed greatly over the last few decades, but our knowledge of “functional anatomy” has. Single limb training is a logical outgrowth of what we now know about functional anatomy. It promotes greater muscle growth and greater muscle strength because it works more muscles. Knowing the way the body works allows us to develop and utilize exercises that work not just prime movers, but stabilizers and neutralizers.
The anatomical evidence for single leg exercise is overwhelming. When we stand on one leg, as in a one leg squat, we engage three muscles that we don’t use in a two leg squat, i.e. gluteus medius, the adductors, and the quadratus lumborum. I know some will say we use the adductors because the knees move apart in the descent, but this isn’t the same. The key is that we engage these additional muscles in their normal role of stabilizers, not as movers.
In addition, in any single leg exercise, bodyweight becomes a more significant part of the resistance. Therefore, we get functional training, i.e. training the muscles that we’re using in the way that we use them. Bottom line: this doesn’t happen in any version of the double leg squat.
In a conventional double leg squat, we simply strengthen the prime movers and neglect the stabilizers. Using the car analogy, we get a bigger engine, but maybe bad tires. Double leg strength also doesn’t correlate to single leg strength. I can’t tell you how many clients I have seen that can squat a large amount of weight yet can’t do a single leg squat. The reality is that they lack “functional strength.”
Very little in life or sport is done with two feet on the ground - think about all sports that require running. In terms of program analysis single leg training breaks down the same as double leg training; we have knee dominant and hip dominant exercises.
Knee Dominant Single Leg Training
All of the squat variations fall under the category of knee dominant single leg exercises. lunges, step-ups, split squats, Bulgarian split squats and true one leg squats (pistols) are all examples of knee dominant single leg exercises.
The great part about these exercises is that it’s really hard to make them into glute or lower back exercises. Not true with the back squat. The really beneficial (and really difficult) knee-dominant single leg exercises are what we call single leg unsupported.
Static, unsupported single leg exercises consist of single leg movements done on one leg with no movement forward or back. To further explain, a lunge would be dynamic as the center of gravity moves forward and back. It’s supported, as the non-working foot is in contact with the ground. In an unsupported single leg exercise, the non-working extremity isn’t allowed to touch the ground or any other object such as a bench. The only true static unsupported exercises are variations of one leg squats. These may be referred to as pistols, one leg squats, balance squats, or step-downs in various texts.
More and more evidence points to the relationship of the hip rotators and the glute medius to overuse knee problems. In static supported exercises (Bulgarian split squats) the hip rotators and glute medius don’t take an active role in stabilizing the femur. In true static unsupported exercises, the hip rotators and glute medius must actively work to prevent internal rotation of the femur. The exercises are essentially tri-planar as the movement may be sagittal, but the stabilizers must prevent movement in the frontal and transverse plane. Any static unsupported exercise automatically becomes a tri-planar movement as the stabilizers work as what we call anti-rotators.
The bottom line is, more muscles work in an unsupported one leg squat. Either way, if you’re looking for assistance exercises to work more muscle and improve performance, forget extensions and leg presses and add in some one leg squat variations. I’ll bet you that if you don’t know where your glute medius is today, you will after your first day of one leg squats!
Hip Dominant Single Leg Training
The interesting thing about hip dominant single leg training is that it’s in fact not only single limb, but single joint. For years we’ve heard the gurus say that single joint exercises are a waste of time. We advocated multi-joint movements as they gave us the most “bang for the buck.”
Over time, I’ve realized that it’s not about how many joints work as it is about how many muscles work. The “no single joint exercises” mantra may be an oversimplification. I may dislike a lateral raise or a leg extension because it isolates a single muscle in a non-functional manner, but I love one leg straight leg Deadlifts.
In truth, a one leg straight leg deadlift is a single joint exercise. What makes it better than a leg extension or a leg curl? The number of muscles working. It’s not about the number of joints that are moving; it’s about the combined action of moving a joint in one plane while stabilizing in two others.
In the one leg straight leg deadlift, the action is a sagittal plane hip hinge. However, the spinal erectors, lower traps, and rhomboids must work to stabilize the spine and the scapula. The hip rotators and pelvic stabilizers work to keep the pelvis moving in the sagittal plane.
What appears to be a relatively simple single joint exercise is actually an extremely complex exercise in muscle synergy that incorporates a huge amount of muscle. In addition, one leg straight leg deadlifts provide great stress to the glutes and hamstrings while providing 50% less back stress.
The same can be said for the swissball leg curl. Once again we have a single joint action. In fact, biomechanically, some would claim that it’s the same action as a prone machine leg curl. However, in actuality the swissball leg curl is a far superior exercise. Why? because the glutes and hamstrings must work together to hold the hip in extension while the hamstring works alone to flex the knee. The swissball leg curl in effect forces the hamstring to work from both ends in its two joint function as a synergist of hip extension and a prime mover in knee flexion.
Conclusion
I am not saying “single joint is bad, multi joint is good or vice versa as they both have there place.” What I am saying is that if you’re an athlete training to improve performance and reduce injury potential, or a bodybuilder looking to stress some little used muscles, give one leg squats, one leg straight leg deadlifts, and swiss ball leg curls a try.
