One of the drawbacks of having a broad range of exercises available is in determining which exercise is appropriate for which individual and, at what point in training should we use them. Hopefully this article will promote some further thought on the appropriate use of single leg exercises.
Presently we see exercises like lunges, which I would consider an advanced exercise capable of producing extreme soreness, recommended as a cure-all for nearly every lower body issue. The current thought seems to be 'when in doubt, lunge". In reality prescribing an advanced single leg exercise like a lunge for beginner can be a crippling introduction to the world of unilateral training.
When looking at single leg exercises it initially becomes apparent that single leg exercises can be broken down into knee dominant exercises, or those that appear to be variations of a squatting movement and, hip dominant exercises, or, those that appear to prioritize the glutes and hamstrings and generally appear to be variations of straight leg deadlifts or bridging exercises.
After further investigation of the demands of single leg exercises it appears to become necessary to break single leg knee dominant exercises down into static exercises (one leg squats and variations) and dynamic exercises (lunges and slideboard lunges). In a static single leg exercise there is no movement of the feet. One or both feet stay in contact with the ground. The body moves up and down in the sagittal plane or potentially side to side in the frontal plane, as in a lateral squat. Static knee dominant exercise can further be broken down into either static unsupported or static supported exercises.
Static Unsupported Single Leg Exercise- Static unsupported single leg exercises consist of single leg movements done on one leg only. The remaining extremity is not 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 one leg squats, balance squats or step-downs in various texts.
Until recently, I did not feel it was necessary to distinguish between a static unsupported exercise and a static supported exercise. However, Strength and Conditioning Coach Karen Wood convinced me otherwise. Wood's rational was that there was limited functional carryover from the single leg supported category to the single leg unsupported category. In other words performance of exercises like splits squats or rear foot elevated split squats (Bulgarian Lunges in the literature) did not seem to carryover to performance in a true one leg squat.
More and more evidence points to the relationship of the hip rotators and the glute medius to overuse knee problems . In static supported exercises the hip rotators and glute medius take a less active role in stabilizing the femur. In true static unsupported exercises, the hip rotators and glute medius must actively work to prevent adduction and internal rotation of the femur. The static unsupported one leg squats are essentially tri-planar as the movement itself may be sagittal but, the stabilizers must prevent movement in the frontal and transverse plane. A static unsupported exercise automatically becomes a tri-planar movement as the stabilizers work as what we call anti-rotators. Wood's thought process has caused me to perform exercises in a manner we now define as progressive range of motion.
Progressive Range of Motion Exercise- Earlier in my career I would have scoffed at the idea of using any type of partial movement. However, as I became involved in the rehabilitation of athletes with patella-femoral problems I came to realize that in the lower body, range of motion needs to initially take a back seat to femoral control. Often in static supported exercises like a split squat or a rear foot elevated split squat (frequently called Bulgarian lunges ) the athlete or client can move through a full range of motion, often with significant loads, but is still unable to control the motion of the femur in an unsupported environment. In this case, lower body strength is wasted because it does not fulfill its obligation to control the motion of the femur. To illustrate the concept, a single leg squat would be done only to the depth that is both pain free and that demonstrates control of the femur relative to adduction and internal rotation. In other words it is not enough to squat low, the trainee must squat low while maintaining control of the femur from the hip. In progressive range of motion training the load (bodyweight) remains constant while the range of motion is progressively increased. Once the trainee demonstrates full controlled range of motion the programming reverts to basic progressive resistance concepts. Therefore we may simultaneously (in the same program or in the same workout) be performing a single leg unsupported exercise using progressive range of motion ( partial one leg squats) followed by a single leg supported exercise done through a full range of motion.
Single Leg Supported Exercise- Although single leg supported exercises have been alluded to above a more detailed explanation is necessary. Single leg supported exercises describe a single leg exercise done with some level of support from the remaining leg. The non-working leg could either be in contact with the floor as in a split squat or, on a bench or specially designed stand as in a rear foot elevated split squat.
They are not by definition dynamic exercises as they lack translation. The center of mass stays with in the confines of the base of support and the feet do not move. Examples include the split squat seen in figure 2, the rear foot elevated split squat alluded to previously and seen as figure 3, the lateral squat ( figure 4) and a rotational squat ( figure 5).
Single leg supported exercises are a great introduction to single leg training and should always precede the dynamic variations. In other words split squats should precede lunges, lateral squats should precede lateral lunges, and rotational squats should precede rotational or transverse lunges. Failure to do this will result in exceptional soreness, possible disruption of the training program, and often a loss of confidence in the coach or trainer by the athlete or trainee. The reason for the exceptional soreness lies in the sagittal emphasis of most training programs. Many times range of motion is consistently gained in the same plane of motion and motion out of the sagittal plane involves muscle fibers and action never previously encountered.
Figure 3 - rear foot elevated split squat, AKA Bulgarian lunge An additional benefit of single leg supported exercise is that these exercises are excellent for flexibility. In fact many of the single leg unsupported exercises are frequently used as dynamic warm-up exercises and are excellent for more experienced trainees in that function.
Figure 4 - Lateral Squat
Figure 5- Rotational Squat
It is important to add here that some coaches have begun to argue that a static supported single leg exercise is then not by definition single leg. This to me is a semantical argument that appears to be just be for arguments sake. It is like saying an outrigger canoe is no longer a canoe because of the outrigger. Both static supported and static unsupported exercises have value.