Base of Support and How it Impacts Balance

Base of support is defined as the area beneath a person that includes every point of contact that person makes with the supporting surface. This means that when you are standing, your base of support is the area between your two feet. The wider your feet are positioned, the easier it is to balance. In this blog post, we will discuss how and why we modify and vary our base of support in order to help compensate and improve or to challenge our balance.

When we alter our base of support, it also alters our stability. The wider our base of support is (meaning the farther apart our feet are) the more stable we will be and feel. The more narrow our base of support is (meaning the closer our feet are together) the more unstable or off balance we may feel. Think about the “ready stance” that athletes assume in most sports. They typically have some bend in their knees, and their feet are apart. This is a very stable position to be in! Throughout the day, we all stand in different positions and may find ourselves with a more narrow stance at times, and a wider stance at other times. For this reason, when someone is having difficulty with their balance, it is important to train balance in various positions including both wide and narrow stance positions.

Everyone’s balance is different and we all have varying margins for how much we can move our body and still maintain balance. This is called our limits of stability - or how far outside of our base of support we can move and still maintain balance. In physical therapy, our goal is to improve each individual’s limits of stability so that they feel more stable and balanced in their daily life.

The above photo demonstrates the concept of limits of stability and how this can vary from person to person. In both image A and B, the base of support is the same. However, in image B, the individual has a much larger limit of stability (as indicated by the red circle). In physical therapy, our goal is to increase an individuals limits of stability to reduce the risk for falls.

How do we improve one’s limits of stability? By challenging it! In order to be more stable throughout daily life, it is important to perform balance exercises that are challenging but doable. Balance exercises should be performed both statically and dynamically. Static balance involves holding your balance in a stationary position. An example of how to challenge your base of support and limits of stability in static balance is standing with one foot in front of the other (heel to toe) while reaching with your arms forwards, backwards and side to side as far as you can while maintaining balance. Dynamic balance involves maintaining balance while moving. An example of how to challenge your base of support dynamically is walking heel to toe forwards.

As we mentioned above, the more narrow your stance is, the more challenging a balance exercise will be. When starting with balance exercises, it is best to begin with a wider stance and progress slowly to a more narrow stance and eventually to standing on one leg when able. Below is a photo that demonstrates this progression.

While we want to challenge your balance safely while in a physical therapy or wellness program, it is also important to consider safety during your daily activities if you are having trouble with balance. If you feel unstable throughout the day or during certain activities, you can use your base of support to your advantage by widening your stance. When the center line of gravity running through your body lands between your base of support, you will feel much more stable! This is depicted in the photo below. When one is leaning forward for an object (as in image B and C) the center line of gravity is in front and outside of the base of support creating instability. Think about this whenever you are reaching for something or picking something up from the floor. The closer you can move your body to the object, the more you can move that center of gravity so that it is within your base of support thus resulting in a more stable posture.

Another compensatory strategy to help increase one’s base of support is to use an assistive device. While assistive devices provide good feedback and upper extremity support, they can also make you more stable by widening your base of support and therefore increasing your limits of stability through another point of contact with the floor. This is demonstrated in the photo below. Image C shows what happens when someone uses a walking stick (depicted as the blue circle) and how this widens one’s base of support in comparison to standing on one leg (image A) and standing with feet about shoulder width distance apart (image B).

If you have any questions about how to vary your base of support for balance training or how to increase your limits of stability to improve safety and prevent falls, please reach out to us here. For more ideas on how to best incorporate balance training exercises with varying your base of support, check out our balance classes on Wednesdays over zoom!

Phu, S et al, 2020. Postural instability - Balance, posture and gait. Encyclopedia of Biomedical Gerontology (pp.64-76). Publisher: Elsevier.