Standing balance is one's ability to remain upright and steady. Steadiness is maintaining the body's center of pressure (COP) well within the base of support (BOS). Steadiness is characterized by the absence of significant swaying, stepping, reaching, or holding. When balance is challenged (slips, trips, nudges, extended reaches, narrow stances, etc.), the risk of falling increases. Proportionally, the bigger the challenge, the bigger the COP movement, and the greater the risk of falling. Fortunately, the body has 4 natural defenses to fight against falls. These defenses are called as "balance reactions," and they differ depending on the degree to which balance is challenged.
- Ankle Strategy. For "small" balance challenges, the ankle strategy is the body's first line of defense against falls. The ankle strategy is made up of coordinated contractions of muscles around the ankle to oppose COP deviations. For example, if the body sways backward, muscles on the front of the ankle contract to pull the COP forward. Conversely, if the sway is forward, muscles on back of ankle contract and pull the COP backward. Variations in ankle strategy occur during standing with small, imperceptible corrections happening all the time to keep the body's COP well within the BOS.
- Hip Strategy. For "medium" balance challenges, the hip strategy is the body's next line of defense against falls. While muscle contractions are integral to hip strategies, these strategies are better characterized by examining the movements of the hips and arms. For example, a loss of balance going backwards results in the hips quickly extending and creating a back-bending movement. At the same time, the arms quickly elevate up and forward. The result looks like a limbo motion when ducking under a bar, only much faster. The net effect of the hip and arm motions is to slow down the body's COP movement (which is going down and back) and redirect it forward, helping to regain balance. Conversely, for losses of balance going forward, the hips will quickly flex and the arms extend up and back. The effect is a slowing and redirection of the COP. The result looks like someone quickly taking a bow after a play while simultaneously extending their arms back like a ski jumper. Hip strategies occur quickly and typically only happen when the COP nears the edges of the BOS.
- Stepping Strategy. For "large" balance challenges, stepping strategies are the body's best line of defense against falls. As the name indicates, stepping strategies occur when you take a step (or two) to prevent falling. The goal is to change the position of the feet, establish a new BOS, and steady the body. In this strategy, the loss of balance is large (the COP exceeded past the original BOS), and new base has to be established to keep from falling. In stepping strategies, the ability to take a quick and controlled steps is key to effectively recovering balance and preventing falls.
- Reaching/Grabbing Strategy. The last line of defense against falls is the reaching/grabbing strategy. This strategy is defined by reaching out and trying to grab anything nearby, to keep from falling down. It is typically only used when ankle, hip, and stepping strategies are not effective.
In respect to rehabilitation, I've noticed a few trends. In my opinion, patients tend to overly rely on ankle strategies. They use them to correct for medium or large balance disturbances, but they are really only designed to be effective for small ones. They also tend to skip over hip strategies - unknowingly leaving out their best defense against medium level balance disturbances. Additionally, patients are often ineffective with properly executing stepping strategies. They may lack the coordination and/or leg and trunk strength needed to step quickly and sturdily. Lastly, I see patients using reaching/grabbing strategies too frequently. Reaching and grabbing is typically a last-resort strategy. However, patients will often start reaching and grabbing when their ankle strategies haven't helped, skipping over hip and stepping strategies all together! It is in helping patient regain the effective use of their hip and stepping strategies where I see the biggest opportunities for therapists to help patients. Stay tuned for the next blog post or two, as I will attempt to provide practical examples on improving hip and stepping strategies.
NOTE: Shane Haas, PT, MSIE, CPE will be in Dallas, TX on February 24th 2018 teaching Balance Training by ADL. If you are interested in joining use for a great course, please visit www.ADLbalance.com for details.