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Load and Capacity | Find the right dosage

This is originally an idea I read from the BJSM(British Journal of Sports Medicine), a blogpost written by Tom Goom @runningphysio and by Kevin Maggs @RunningReform. Not only does it apply to tendinopathy but also on issues like lower back pain, neck pain or general sports injury. Similar to the idea of ‘overloading’ in modern training concepts. In order to grow stronger and lift heavier, one must try to accomplish one more rep or add another 10lb plate for it to count as progress. A progress that is physical, that serves as a mark of improvement. So as a physio in my own office, I tried my best to explain to my patients, that having one leg longer than other, or one vertebra stacking not perfectly on top of another is not the source of pain. Rather, loading too much of the body can take is the source of pain.

Load is essentially stress, or pressure on joints on the body. It can be sitting at the desk, riding a bike or reading a book for too long. Load might be not in the form of numerical value. As it often is expressed in a form of activity, or psychologically, load can be tangible or intangible.Capacity, on the other hand, is the ability of someone to perceive, cushion or handle the load. It varies from person to person

This Load/Capacity model entails the social spectrum of the biopsychosocial model which is always too difficult to quantify how much is too much. It is seemingly impossible to say and compare 1 hour office clerk work is more stressful than 2 hours. Or lifting weights faster for 3 mins is more strenuous than lifting heavier weights slower for 2 mins. The upside of this model is that we, as healthcare professionals, are able to explain and elaborate on the cause of pain is not just due to one or multiple biomechanical ‘flaws’. Having pain without an identifiable reason is inequivalent to complete cessation of activities. Similarly, just because squatting with knee pain means the knee is doing more damage than harm. Pain is subjective, in a form of neural sensation, often tells an alarming signal of “ Stop, you are hurting yourself”, but instead these sensations are merely just a bundle of many factors that includes psychological and social behaviours.

By utilizing this model fear instilled by medical diagnosis that has led to kinesiophobia can show patients how graded exposure to loading is better than complete activity avoidance. Here is a figure I have found on an editorial written by Kieran O’Sullivan and Peter O’Sullivan, title “ Pain and fatigue in sport : are they so different? “

Under-loading reduces the capacity of an athlete. This creates the idea of avoiding certain activity or training movements and fear of it. For example, in my clinic patients come in complaining of lifting the arm up from the side with pain, or shoulder pressing movement creates pain. Such sensation of pain generates the thought of vulnerability and fragility. Patients take a step back from routine training schedule and doing nothing. If we ignore the pain signal and keep pushing the patient, we are likely to do more harm than good. The best approach is to find the right dosage. By identifying the main problem, through active listening and positive communication, athletes can maintain certain level of activity without compromising the capacity of recovery.

A very common example of this is take the same client who came in the clinic complaining of pain lifting the arm up from the side. One possible explanation of the pain is rotator-cuff related shoulder pain(RCRSP) due to overuse of the rotator cuff muscles. To apply the same principle of load/capacity model, modification to choices of training exercise and de-loading will be a good strategy. I recommend that athletes instead of doing lateral dumbbell raises, machine side raises with a shorter lever arm puts less stress on the shoulder; instead of jumping straight into workout, do 10 minutes of rehabilitative exercises of moderate loading to test if the shoulder joint is ready for a workout of higher intensity.

Here is a brief infographic I did to illustrate how load and capacity can lead to injury or recovery

When loading exceeds capacity, pain will follow. Vice versa. The goal of physical therapy is take you out of pain to full recovery. With appropriate load modification, that includes adding variation of exercise into the training program, tracking volume/intensity of every workout session, sleep and life stress management and capacity development. Loading the tissues gradually will increase tissue capacity until where it reaches beyond or equal to maximum loading tolerance. This is the best, and by evidence the most scientific to conduct rehabilitation and physical therapy.

CLOSING THOUGTHS: Clinicians in Taiwan are still heavily married to manual therapy, and modalities, as mainstream physical therapy. There has to be a shift in more physical therapy practice to exercise and active interventions. The load/capacity model is by far one of the best to start with, for both new young physical therapists and experienced professors alike. It is something not taught in a lecture in PT school. Basic communication, sentient touch and logical mindset is what comes before finding the structural flaw, or the distressed tissue, when analyzing a problem with a well balanced biopsychosocial model.


James Au (@jamesthephysio) grew up in Hong Kong and is currently a full-time physical therapist registered in Taiwan, and a strength and conditioning specialist. He is the founder of the ACL CLUB TAIPEI and a speaker for multiple fitness centers in Taiwan.

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