Get Your Power Back After An Injury!
Are you having trouble regaining your quick first step following an injury? Do you consistently struggle to produce force with one shoulder? Is there a reason why a recent study shows that only 55-70% of athlete’s recovering from ACL Reconstruction do not return to competitive sport (Ardern et al 2014.) I believe that a common reason is that much of today’s current rehabilitation model doesn’t ask an athlete to challenge his or her nervous system in the way necessary to produce force…fast! Let’s dive into this concept at multiple levels.
Muscles are like obedient dogs, they do what they are told to do by their master…in the human body this is the nervous system. If the nerves innervating a muscle tell that muscle to contract, an intricate chemical cascade will fire allowing a muscle to shorten and produce force. If that same nerve removes the stimulus to contract, that chemical cascade will stop, and the muscle will “relax” and lengthen. Nerves innervate every muscle in our body and are the only reason why a muscle will contract or relax.
Any time the body has an injury, the brain and nervous system senses a threat or change to the body’s balance known as “homeostasis.” The brain and nervous system go into a protective state where it may “inhibit” or shut off the nerves to some muscles surrounding the injured area. In a larger instance of threat or change (such as a more severe injury or surgery) the body will have a more severe response to shut off muscles to the surrounding area in an attempt to minimize collateral damage. When our muscles don’t work as well, we cannot adapt and push to return to full activities, therefore self-limiting our body from subsequent harmful activities.
Once sufficient time and interventions have been utilized to allow the body to heal, the sense of threat to the body is severely diminished and muscles may begin to turn back on. It is my belief that physical therapy as a profession (whether knowing it or not) has been defined as being able to acknowledge which muscles need to be “turned back on” following an injury and attempting to provide the stimulus needed to allow full return of these muscles. I would argue that two large parts of fully returning our patients’ to sport are…
1. Encouraging the physiological demands of muscles to be prepared for demands of sports.
2. Assuring the nervous system is appropriately ready to turn these muscles on…..fast!
The physiologic demands of muscles can be defined in simplest terms as having the expected length, strength, and the ability to “turn on” to perform the expected tasks of each sport. The length needs to allow an athlete the ability to get into the expected positions needed for optimal performance. The strength component serves as the baseline measure of the muscles ability to produce force. If the muscle has limited strength, the amount of power (producing force….fast) will also be significantly limited. There have been many publications that express the expectations for basic lifts, such as bench and squat, for athletes regarding age/position that can help gauge baseline strength. One such example is Speed & Strength Ratings by Dale Harder, which publishes such statistics as….
–A 165 lb high school lettering male athlete should have an average max squat of 270 lbs. and average max bench of 190 lbs.–
If an athlete is not anywhere near his or her expectation of this 50th percentile of strength, I can not expect optimized power output due to decreased baseline strength.
If an athlete has sufficient baseline strength, it’s time to assure that we have adequately stimulated the nervous system to produce this muscular force…fast. This brings us to a concept of Rate Coding. Rate coding can be described as the relationship between sensory stimuli and the response of the nerves to those stimuli. Simply put…I want to turn this muscle on to move my body this way and how fast can the nerves turn this muscle on. The theory of rate coding measuring is how many times can you create a nerve response to the stimulus in a given amount of time…and yes, in the instances of sports we’re talking milliseconds.
To ensure that an athlete can produce a given amount of force…fast, it is my belief that we need to challenge the nervous system through the theory of rate coding. If the nerves innervating the muscles of a limb have never been asked to move fast, they will not be efficient at producing the expected force when needed. If I want turn on glutes, quads, gastroc/soleus complex and blast into my 100m sprint, I better have trained the nerves to activate into triple extension or my performance will be limited. The theory surrounding training rate coding is that, when stimulated appropriately, we can tap into the nervous system faster and have the nerves controlling the muscles turn on faster. This will lead to increased power output.
Power = Work/Time
Work = Force x Displacement
Much of an athlete’s physical success in any sport is defined by power. How well can they move a limb, or another body, or an object in the least amount of time?
When performing rehabilitation in athletes today, we as a medical community need to recognize the importance of stimulating the nervous system and allowing an athlete to produce the force they need…fast. This will not only allow our athletes to have an increased overall perception of physical function, but will allow your athletes to thrive on the field.
Depending on the sport, the training of rating coding and power production can look very different. Commonly seen in the strength and conditioning literature, there is a force-velocity relationship curve that shows the expectations for balance with force of movement and speed of movement.
The Force-Velocity Curve
This chart shows the inverse relationship that exists between force production and velocity of movement. As force increases, the speed expected in a movement will significantly decrease. Vice-versa, if the load is significantly less, than the speed with the speed of movement performed should go up. Remember, regardless of the load, the INTENT of the training intervention is to move the weight as fast as possible!
TEACHING POINT: How does this apply to me as an athlete?
Is the same power intervention appropriate for an elite dancer as my offensive lineman? Any power movement will fall somewhere along the curve and will work to increase overall power output, but to allow an athlete to best perform at his/her expected sport, it is ideal to match the power movement with the physical demands for a sport during the peaking phase of training. For example, medicine ball rotational throws in a diagonal pattern may mimic the jumps required for her routine more than a traditional power clean. My offensive lineman may benefit more from my traditional power clean to explode off the line and push a 300+ defensive lineman on a run blocking play.
Why Should I Train at Different Loads?
Here are some examples of different exercises at different points of the curve.
Take Home Points:
-Injury will decrease the way that I turn muscles on and how much force they can produce.
-Once healed, these nerves need to be turned back on.
-I need to have appropriate baseline length and strength. (Yes, many norms in strength are published.)
-The nervous system can be used to help me express my strength fast.
-I can use various types of power training to help me produce force…fast!