by Mitch Hauschildt, MA, ATC, CSCS
I often use the Law of Irradiation to help my patients load movement appropriately and also to prime the nervous system either prior to complex movements or during a workout in general.
Sherrington’s Law of Irradiation states that a muscle working hard recruits the neighboring muscles, and if they are already part of the action, it amplifies their strength. The neural impulses emitted by the contracting muscle reach other muscles and ‘turn them on’ as an electric current starts a motor.
What this basically means is that if we load the system (we can define load a number of ways) to make muscles “work hard”, then we get some great effects throughout the chain that help us improve motor control, stability and movement in general.
One easy example of the law of irradiation is a farmers carry. I have written about carries in the past, as they are one of my favorite exercises. By placing a heavy load in the hands and asking someone to move, we experience an increase in stability proximally. Because the muscles in the hands and arms are working hard, we then get an activation proximally in an effort to assist with the task at hand. I consider carries a moving plank.
I’m always looking for good ways to upregulate the nervous system to improve stability and motor control. One of my favorite methods is whole body vibration. Standing on a vibration platform is a great way to prime the nervous system because research supports this modality as a means to effectively turn on the system as either a priming exercise or part of a training superset to help with power output and strength.
But, what if you don’t have a vibration platform? Or, what if you really want to use vibration in a specific area. This is where I like to use percussive massage units. There are a number of units out there with a wide range of prices, settings, and noise levels. I prefer the Hypervolt for a lot of reasons, but in this instance, I like it because of its 3 speed settings. But, feel free to use what you have access to.
I utilize these massage units on the palm and the bottom of the foot when I want to promote more stability and motor control in that extremity. For example, when I have a patient with shoulder impingement, I have the patient lock out their arm, pack their shoulder in front of them and apply percussion (vibration) through the palm of the hand. This vibration does 2 things:
- We know that there are a lot of Paccinian Corpuscles in the palm of the hand (and bottom of the foot). These mechanoreceptors respond well to rapid pressure changes and vibration and they are responsible for priming the nervous system in general. Stimulating these mechanoreceptors through the palm of the hand (or bottom of the foot) will stimulate the nervous system in general.
- Vibration through a limb provides a fairly high load. If you don’t believe me, try performing a plank on a vibration platform for a while. It is a whole lot harder than on the ground. The repetitive on/off over and over stimulates muscle activity and creates a sizable load. With this load through the hand and arm (or foot and leg), you will find an sizable stimulus to the shoulder stabilizers and trunk (or hip and trunk).
The keys are to perform them with a moderate pressure and I find that the low and medium settings are the best. You don’t want to make it painful or uncomfortable, but you also need a significant enough load to make things radiate. It also doesn’t take a lot of time. Ten to 20 seconds at a time is about all you need.
Here is a video explaining how it works:
Use vibration irradiation early in a training session to assist with movement prep. Or you can use it within a workout to improve neurological efficiency. It is safe, simple and effective.
Leave a Reply