Inflammation is having a moment. Perhaps due to COVID-19 and the puzzling inflammatory cascade, all health practitioners are diving a bit deeper into the role of inflammation in illness and healing. With that in mind, we present this review of the function of inflammation in acute musculoskeletal injuries. An understanding of injury starts with a... MORE
Bringing training principles to the rehab gym
A recent Sports Injury Bulletin article by Jason Tee explored the complexities of injury prevention programs. He likened injury prevention to taking out an insurance policy to keep injuries from occurring in otherwise healthy athletes. However, do injury prevention principles, particularly the measurement of training load, have a place in the rehabilitation of an already injured athlete?
Athletes with musculotendinous injuries usually suffer damage as a result of either over-training or under-training. Over-training places a chronic burden on the tissues that exceeds their loading capacity. Under-training results in injury from acute stress that the tissues weren’t ready to handle. Healing tissues, especially tendons, respond to loading – particularly heavy slow resistance training. However, even the rehab course must take into consideration the readiness of the muscles and tendons to handle loads.
How to measure training loads
External training loads are readily measurable. For instance, it’s easy to calculate the amount of work done by factoring in aspects such as resistance, rate, reps, or distance. Internal training load, on the other hand, is less easy to gauge. It depends on the physiological or perceptual response to the work done. Some aspects of internal training load are an athlete’s perception of the difficulty of the task, heart rate, age, injury history, hydration, and diet.
Thus, the same external loads will produce differing internal loads depending on the athlete. For instance, imagine two athletes in the gym performing a short-arc-quadriceps exercise to strengthen the vastus medialis obliques (VMO). One is status-post ACL repair, and the other suffers from a quad strain. Both perform the same exercise for three sets of 15 reps and no additional load. Yet, while the external load is the same, the internal load may be completely different. The acute swelling and pain from the ACL repair in a young athlete may delay the firing of the VMO, yet the muscle has the fitness to execute the entire series. The athlete with the quad strain may not feel pain with this exercise, but as a 35-year-old runner with a history of a previous quad injury, he may have to work harder to sustain a very weak VMO for the entire three sets of 15 reps.
Response to training load is individual. Physios should take this into account for each athlete and adjust their rehabilitation program accordingly. Executing activities within a clinical pathway without load adjustment commiserate with the external and internal loads experienced by the athlete may contribute to the high rate of reinjury. The injured tissues may never experience the kinds of loads necessary for healing nor develop the fitness required to withstand the magnitude of loading required in return to sport. On the other hand, overloading in rehab leaves a muscle in a fatigued rather than fit state and highly susceptible to reinjury.
How to progress rehab loading
Athletes who increase their training load more than 10% in a week seem to escalate their chances of injury(1). This rule of thumb works well for most training programs except at the very low end and high end of loading. Say an athlete resumes running after an injury and comfortably runs one mile at a moderate pace. To increase that weekly at 10% would mean adding .1 mile per week, a seemingly ridiculous amount. Athletes typically tolerate a progression of greater than 10% at the low end of loading. Therefore, this approach usually won’t apply to athletes just returning to activity.
There are other methods to assess tolerance to progressive loading. One way is to use post-activity pain as an indicator. Educate the athlete not to confuse delayed onset muscle soreness (DOMS) with pain. Soreness after an increase in load is expected. However, pain that persists for more than 48 hours may indicate that the tissue was over-loaded.
Another way to approach load tolerance is to evaluate the acute:chronic workload ratio. In acute rehabilitation, the chronic load may be more internal than external. The tissues are handling the physiology of healing, which may include inflammation, pain, and decreased blood flow, sensation, and proprioceptive input. Rehabilitation activities, therefore, aren’t started from scratch, but with muscles and tendons already placed under strain.
Typically, chronic training loads are an indicator of fitness; however, in rehabilitation, they may lead to muscle fatigue. Keep this in mind when designing and progressing rehab activities. It’s important to educate the athlete as well. Knowing that their body is already dealing with a substantial load may help adjust expectations for the pace of rehab.
Placing quantifiable units on the training load of healing is difficult. However, keeping a spreadsheet of the rate of perceived exertion (RPE), reps, resistance, position, and pain experienced one to two days afterward for each rehab activity will begin to build a picture of what an individual’s tissues can handle. The rehabilitation process then becomes more tailored, measuring the fitness of a muscle and taking into account the fatigue. Like dollar-cost averaging, an upward trend should emerge in the body’s ability to handle load spikes despite periods of fatigue.
As the rehabilitation process progresses, integrate sport specific-drills and monitor them the same way. Athletes educated during the rehabilitation process to track their training load are empowered to become self-advocates. They have the data to challenge blanket training or coaching agendas and learn to listen to their body. Athletes invested in their wellbeing can establish boundaries that free them from a victim mindset. Making training decisions with tissue tolerance in mind means injuries won’t happen as an uncontrollable consequence of training error. Athlete self-advocacy, through the implementation of training load principles during rehab, could be the secret to decreasing reinjury once they return to sport.
- Br J Sports Med. 2016;50:273-280