Sensory Reweighting & How It Should Influence Your Rehab
In order to move efficiently through the dynamic environments of the real-world, we need to gather sensory information from different systems to help us direct our movement well. And because we are humans, we have the ability to recognize patterns of sensory information and use them to predict the best way to move in a given situation or environment. For today’s post, we want to bring your attention to this concept of “sensory reweighting,” the ability to rely on different streams of sensory information in different environments for movement generation and control. This ability to depend on or trust different sensory inputs, from your eyes, your inner ear, or the feedback from your body, is crucial for you to move well in dynamic environments. We have spoken many times before about the big three sensory systems that our nervous systems uses to generate and control movement, which are:
- Visual System
- Vestibular System
- Proprioceptive System
We can break these systems down into many subsystems, and test their ability to tolerate load. Of course, we should always begin with the proprioceptive system first, and progress towards integrating the higher-order sensory systems first, and the research paper attached explains why this is the case.
This research article dives deep into the rehabilitation of ACL tears, and how we can do a better job in order to reduce the risk of a re-tear. What they tried to do in this study is identify if something was missing from traditional ACL rehab, and what they found was that after an ACL tear, many of those who went back to playing sports relied much more heavily on their VISUAL SYSTEM to generate and control their movement. Now, that might not seem like a big issue, but think about what might happen if an athlete is running down the field, their gaze is directed across to the other side, and they have to quickly plant, twist, and push off from their previously rehabilitated lower limb? What if they jump to catch a ball, and must now collide with the ground with their eyes still directed up to the sky? In those moments, they can’t use their visual system to control what’s happening at the knee and lower limb. This might not be something that comes to the surface during rehab in a gym or clinical environment where its controlled, but in a fast-paced sport with lots of uncertainty, we most certainly want to ensure that they TRUST the information coming from the knee and lower limb. That means we need to identify the load tolerance of the proprioceptive system only, without the use of the visual system.
What they ended up doing in this study, is leveraging this concept of sensory reweighting, and design rehab drills to force the athlete to move without the use of visual feedback, and only the feedback from the proprioceptive system. You can check out the article for specific ideas.
What we wanted to draw your attention to here is that, we can’t just assume that our rehabilitation is making an individual a more robust mover. There’s a lot more happening beneath the surface, and we may not be able to identify these load discrepancies throughout different systems in a safe and controlled environment like a clinic or gym. There are many ways to manipulate the sensory systems to add more LOAD to a movement strategy, because our ultimate goal is to allow the nervous system to trust each source of sensory feedback. If it trusts and can rely on each source of sensory feedback, then it’s potentially much less likely to express any kind of unnecessary protective strategy, such as pain or excessive tension. On top of that, we want to make sure that it can protect us when necessary, by increasing muscle tone when to reduce the load on certain peripheral tissues, which is stressed in the attached paper. In order for our nervous system to direct appropriate motor output, it must receive high quality sensory feedback. As rehab and movement practitioners, we’re in a great position to identify any load discrepancies in these sensory systems, and design rehab progressions that target the unique sensorimotor presentations of each individual we work with.
We are all aware of the need for progressive overload to facilitate necessary adaptation in an individual’s movement system. But, what we can gather from the attached research paper, is that there are many ways to increase the LOAD. We don’t have to only add external load to a movement to facilitate change, but we can manipulate the sensory systems to have a similar impact on the individuals system. We’re big fans of specific vector-based isometrics at IKN, and one of many ways that we can increase the load placed on the proprioceptive system, is by closing the eyes. This is not a case of just closing someone’s eyes to challenge their balance, but during an isometric, have the individual bring their full, conscious attention to the area of pain or injury (don’t think of the pain, but just the body part). Then, have them close their eyes to further push the nervous system to pay attention to the proprioceptive input. This would of course be part of a progression throughout rehab, and you’ll need to ensure that they can coordinate their breath simultaneously. Sometimes, in order to facilitate change, we can’t just whisper to the nervous system, but we must scream at it.