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Load Management and The Envelope of Function



A good physical therapy plan should always equip you with the tools and knowledge to manage your injury or condition beyond the clinic. Whether it is a set of useful exercises, mobility drills, a conceptual framework, or all of the above, there is both power and peace of mind in autonomy. In many cases, the exercises and programming strategies that are used in physical therapy are not only intended to develop strength and stability but also to increase the level of physical stress that a body region can tolerate. Identifying the optimal ratio of stress and rest that your body needs to adapt and recover is the ticket to a successful rehabilitation process.

Physical therapy is the perfect setting to workshop this ratio and to develop a more acute understanding of how your body responds to various inputs. Although it may sound simple enough, in some cases effective load management can be a moving target. Human beings are complicated and there are a myriad of variables that can influence the experience that a person has with their injury or condition. Whether you are a college athlete recovering from an ACL reconstruction or a weekend warrior with nagging lower back soreness, there are no exceptions to this complexity, and so it is important to possess some type of framework to make sense of things. 




The Envelope of Function


A model referred to as “The Envelope of Function” is an excellent place to start. The model illustrates a continuum of activities that range from high stress with low frequency (i.e. jumping from a high ledge and landing on the surface below) to low stress with high frequency (i.e. walking 5 miles around a track). The activities that fall on this continuum, of course, are relative to the individual and their range of physical capabilities. Every individual has an upper and lower physical threshold, and between these thresholds are the various movement demands that you can withstand. In the case of an injury, whether acute or chronic, the envelope narrows and lowers the level of stress that the body can handle before pain sets in. It is important to acknowledge that there are also a variety of non-physical factors that can influence a person’s pain sensitivity, including (but not limited to) stress, anxiety, sleep quality and quantity, and nutrition. To make positive adaptations, a deliberate effort must be made to press into the boundaries of the envelope of function, even when physical ability may seem highly constrained. Using accessible tools like a fitness watch or treadmill can help you to objectively assess and track your capacity with specific tasks. For example, if you are dealing with a chronic issue like achilles tendon pain and jogging has become aggravating, you can use a treadmill to control variables that are relevant to your condition including distance, speed, time, pace, and incline. To find your baseline capacity, choose one of those variables that you’d like to work on and progressively increase it over the course of the session. If you choose speed because transitioning from a walk to a run is typically painful, gradually increase speed until you start to notice that your pain symptoms are escalating to the point where it is too uncomfortable to continue. Record all of the treadmill data at the point at which you stopped the session. Experimenting with the manipulation of isolated exercise or training variables in this manner can provide insight into current physical thresholds, and also create a clearer path to returning to your activity of choice.


Rest and Recovery Time


Rest is also an integral piece of the rehabilitation process, but should be proportional to total workload and training level. Ultimately, physical adaptations can only occur when the body is given the chance to recover. A general rule of thumb is that rest and recovery time should be higher following situations where you have reached closer to the upper threshold of your envelope of function, which typically indicates close proximity to injury, a pain flare-up, or following intense training. As important as relative rest is, it ultimately does not move the needle when it comes to the amount of physical stress that a joint or tissue can handle in the long term. Excessive rest may be detrimental to the recovery process if it is not coupled with a progressive return to movement that reflects the demands of the desired activity or sport.

No two injuries are ever the same and so no two rehabilitation programs should ever be the same. In the presence of pain or injury, it is important to refrain from dwelling on what you can’t do, and instead identify the extent of what you can do. With a good physical therapist and a simple framework like the envelope of function, you can actively work to identify your physical abilities to begin working towards a full recovery.




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