After recently listening to Ben Cormack’s interview on the Physio Explained podcast (1), and his Masterclass on Exercise and Pain (2), it brought home to me that as a profession, our ongoing clinical success is in the ability to guide our patients to participate in the most relevant physical activity for their current and future contexts. This got me thinking about refining my big 3 rules to mastering exercise prescription in physiotherapy; which I teach my 2nd year students at the Australian Catholic University.
As you’ll see, the great thing about these 3 rules is that they can be used to help anyone from Gladys down the road with poor mobility resulting from knee OA and a neurological disorder, to elite level athletes in a return to sport context.
But first, let’s brush up on our exercise science nomenclature
Tempo – speed at which the movement is performed
Time under tension (TUT) – reps x tempo
Volume – a proxy for work performed in a session (sets x reps x load)
Load – external metric measuring the forces placed on and created by the body (e.g. kg, %rm, km/h, m/s, height / length of jump). Or an internal measure of the body’s response to the external load (e.g. RPE, VAS, HR, VO2).
SAID – Specific Adaptations to Imposed Demands. This dictates the type and magnitude of the system’s response to a stimulus.
Progressive overload – a function of increasing work being required over a course of training to drive adaptation. This accounts for adaptive responses, and is what we must think about when applying the following rules to guide our patients to their goals.
RULE 1: Know your biological factors brutally well
This is how you reason what the exercise you prescribe is doing to the tissues.
Arthrokinematics / kinetics (every physio’s favourite) – This is our bread and butter and entails the different muscles, joints, contraction types and associated forces that the body utilises and experiences through movement. This is our expert knowledge of modifying body positions to solve movement problems.
Example Problem – Someone experiencing anterior knee pain at a certain load in a squat.
Example Solution 1 – Sit back into the hips to decrease external flexion moment on the knee to within tissue capacity, instead transferring an increased moment at the hip.
Pro tip – Manipulate exercise selection / range of motion to adjust arthrokinematics (3)
Whole System Kinetics
In the previous example, the arthrokinematics and kinetics have changed where the forces are distributed. But the forces acting on the whole system have stayed relatively the same as long as the tempo has stayed equal through an equivalent displacement of the load.
Example Solution 2 – Don’t change the exercise selection at all, instead change the way the exercise is done to decrease the total system ground reaction forces and impulse to within the knee joints capacity.
Pro tip – To modify system kinetics, play with tempo, time under tension, reps and load. Making adjustments here can bring the whole system kinetics to within a tolerable level for the sensitive tissue without having to change the movement or comprise the stimulus. Think isometrics, and heavy slow resistance for tendinopathy for example.
Biomechanics and kinetics summary – change the way the movement looks to deload a sensitive tissue, or change the way the whole system is loaded to deload a sensitive tissue.
Biochemistry / Cellular Biology
A good pragmatic knowledge of the cellular processes that occur when applying a training stimulus will allow the savvy clinician to get the most bang for their buck with exercise prescription.
The following 3 proposed mechanisms of mechanotransduction outline how muscle tissue adapts to our training stimuli. Knowing these will help you minimise disuse atrophy in rehab.
1 – Mechanical tension: Muscle cells have special proteins on them that detect stretch in the cell membrane. This triggers the muscle protein synthesis response. E.g. you grow more with full range exercise compared to isometric exercises for the same volume of work.
Pro tip – train through a full range of motion and with higher external loads to achieve this.
2 – Muscle damage: When muscle tissue is broken down through high volumes, especially of eccentric exercise, the body goes into repair mode by recruiting surrounding satellite cells. These satellite cells differentiate into more muscle so that a subsequent bout of stress will be spread across more tissue.
Pro tip – increase total volume load and eccentric load to maximise this
3 – Metabolic stress / accumulation: In response to high volumes of work, especially with reduced rest periods, in a muscle certain metabolic by-products accumulate. Chemoreceptors in our hypothalamus pick up the disruption to homeostasis in pH and energy balance, in turn kicking off a hormonal cascade resulting in muscle protein synthesis. Think the burn you feel doing high rep or isometric exercises.
Pro tip – increase TUT, minimise rest, and work at or above lactate threshold to maximise this process.
Example Problem – Acute post-operative rehab
We are often limited by the ground reaction forces or shear / compression forces that can be tolerated. This will mean we can’t apply much mechanical tension or can only create moderate levels of muscle damage (i.e. low external load, decreased ROM, low training volumes / volume loads).
Example Solution – Maximise metabolic stress to maintain an anabolic stimulus – use lower load, decreased range of motion, high TUT, and/or low inter-set recovery periods.
Training cellular biology summary – In most circumstances our patients will not be able to use 1 or 2 of these mechanisms due to injury or pain, so you better know how to maximise the one they can use to minimise the effects of deloading (4-7).
RULE 2: Know the goals of your patient and the exercise – Make sure they match!
Don’t butcher the SAID principle.
This should be the most obvious principle and is probably the one most physios do pretty well at the surface level. We are highly trained at analysing physical tasks and choosing appropriate exercises to help our patients achieve that.
However, specificity relates to the person, not just the tasks. As Ben Cormack describes, our analysis of the person and traits they require help with (e.g. resilience, adherence, kinesiophobia, graded exposure, etc) should also guide our exercise prescription (1,2). Sometimes people need exposure to tough things in exercise to build psychological resilience. Sometimes they need exercise to be flowing, melodic and relaxing as they are already running in high stress mode. Using exercise / movement to facilitate this is something we all need to think about (8,9).
Where I see clinicians and students most struggle in clinical reasoning around the SAID principle, is how to effectively train around an injury.
Example Problem – How do we keep training the athlete struggling with loading closed chain knee dominant exercises, with high enough loads to be protective against further injury?
If we fail here by JUST focusing on low level rehab it often leads to local tissue and systemic deconditioning relative to peers. Resulting in either higher risk of subsequent injury on return to sport, or longer times in rehab.
Example Solution – Find the most specific exercise on the spectrum of lower limb exercises that you can still train with relative high external loads to maintain training tolerance in local tissue, as well as total systemic training load response. Remember there are many ways to vary an exercise to suit the individual, just as there are various exercises to achieve any goal. There is no one right way to squat, deadlift, press etc. Find solutions, not problems. It’s our job to remove barriers by finding the technique that best suits the patient in their context where possible, not the opposite.
RULE 3: Know your patient’s personal preferences
Arguably there is no more important guiding rule here. You can know all of the above and have performed an amazing needs analysis of your patient’s context; but without patient buy in, it won’t work.
Ben states in his podcast that ‘saying exercise does or doesn’t work is like saying food does or doesn’t work’ – it’s a nebulous statement. Food only works if the person eats it and exercise only works if the person actually does it.
I like to use the great Dr Robert Sapolsky’s, of Why Zebra’s Don’t Get Ulcers, famous 4-point checklist to maximise buy-in to my exercise prescription (9).
1- Some level of control / autonomy:
- Likes, dislikes, ability to “feel” the movement, tolerance levels, exercises prescribed and dictated vs. described and collaborated.
2- A sense of belonging:
- Shared patient-centred journey vs. going it alone.
3- Some sense of predictability:
- Rough prognosis, what if they do the intervention, what if they don’t, acceptable pain levels, barometers for improvement, progressions and regressions.
4- An outlet from life’s stress:
- Program should fit into the patient’s life, not add undue stress
To summarise, here are my 3 rules of exercise prescription in shorthand:
1 – Know the biological impacts that exercise has and how the body adapts in response.
2 – Know the goals of your patient and your exercise prescription.
AND MOST IMPORTANTLY
3 – Know the personal preferences of the person in front of you.