As the Yass Method has received more attention it has drawn more people from farther away giving me a greater opportunity to see what types of treatment are being provided widely. One of the most common exercises provided in an attempt to resolve symptoms is the ball squeeze between the legs. It seems to be a fairly widely used exercise as part of the general type of exercise provided when there is a view that exercise should be incorporated in the treatment protocol. Not only is this exercise ineffective in resolving pain but it actually has a deleterious affect which can sustain pain and lead to an increased fall risk.
The premise of the exercise is to strengthen the hip adductor muscles (Figure 2). This the muscles between the legs. I can only imagine that this comes from the theory of strengthening opposing muscle groups like the biceps and triceps, the quadriceps and the hamstrings and in this case the abductor and adductor muscles. Within the Yass Method is the idea that if you are trying to perform functional activities and are getting symptoms by definition some muscle or muscles are not strong enough or are imbalanced to where muscles are straining eliciting symptoms. The goal of diagnostics is to identify just the right muscles that are required to be strengthened so full strength and balance of all muscles is achieved and function can be achieved without symptom. In the case of the hip abductor muscles (Figure 1- muscles that pull the legs out away from the midline and also support you) it would hard to find anybody who has weaker adductors (groin muscles) then abductor muscles (muscles that sit above the hip joint on the side of the pelvis). In most cases the hip abductor muscles are significantly weaker than the adductor muscles. Strengthening of the adductor muscles will only feed into this imbalance. By sustaining this imbalance, the legs are pulled closer together when standing or when walking. This is critical because when standing or walking you want you feet to be below the hip. This causes the leg to be vertical to the ground allowing the skeleton to support a large portion of the body weight making muscle usage much more efficient. If the feet are pulled together, then the legs are angled in and limit skeletal support causing all the muscles including the hip abductors and lower back muscles to have to overwork. What is more important and dangerous is that this moving together the feet during stance or while walking decreases the lateral base of support of the person. This means that the person is more susceptible to falling. A successful base of support is one in which the feet are below the hips.
I have absolutely no idea where the ball squeeze between the knees came from but I see absolutely no benefit from it and if anything I feel it sustains the chance of symptom sustaining and decreases functional capacity. More importantly it can lead to a greater chance for fall risk by bringing the feet closer together as the adductor muscles shorten due to their over strengthened condition in relation to the hip abductors.
Knowing which muscles to strengthen and why is the only way to resolve your symptoms and return you to full functional capacity when the cause is muscular. The information I provide is as guidance for you to understand what you need to do to achieve your goals. I cannot account for why things are performed by others. I can only provide the theoretical basis for what should be done so you have a chance to protect yourself and get the right information to move you forward. Remember, the system will not change for you, you will have to change the system.