Rehabilitation Isn't Just About Getting Stronger

Written By Wayne Armour

How we progressively teach the body to tolerate, control, absorb and produce force.

When people hear the word rehabilitation, they usually think about getting rid of pain. Maybe you have injured yourself. Maybe you have had surgery. Maybe something has been niggling away for months. Or maybe you are moving again, but you do not quite trust your body to do what you used to ask of it. This is where rehabilitation gets interesting. Rehabilitation is not simply about finding an exercise that makes something feel better. It is about rebuilding capacity. Your body needs to progressively learn to tolerate load, produce force, control movement, absorb force and eventually respond at the speed and intensity that your life actually demands.

That is why I often think about rehabilitation through three broad types of loading:

ISOMETRIC -> ECCENTRIC -> PLYOMETRIC

Before anyone decides that I have invented a three-step recipe, let me stop you there. This is not a universal sequence. Not every injury starts with an isometric exercise. Not every person moves through these stages in this order. Not everybody needs plyometrics. Rehabilitation should be based on the individual, including the tissue involved, the injury, current capacity, symptoms, training history and what the person is actually trying to get back to. Clinical guidelines increasingly support criterion-based progression rather than progressing simply because a certain number of weeks have passed. This is best demonstrated in return-to-sport rehabilitation, where strength, movement quality, functional performance and psychological readiness all contribute to the decision (Meredith et al., 2020; van Melick et al., 2016).

Think of these three methods as different tools for progressively challenging the body. At its simplest:

  • ISOMETRIC: Can you tolerate force?

  • ECCENTRIC: Can you control force?

  • PLYOMETRIC: Can you produce and absorb force quickly?

That is the part I want you to understand. Once you know why you are doing an exercise, the exercise starts to make much more sense.

1. ISOMETRIC: Establishing force and control

An isometric contraction occurs when a muscle produces force with little or no visible movement at the joint. Consider holding a wall sit: your muscles work under load to produce force without repeatedly moving through the joint range. Isometric exercise is utilised in both rehabilitation and physical preparation to drive muscular, strength and neuromuscular adaptations. However, because the response depends heavily on variables such as muscle length, intensity and intent, the word "isometric" on its own reveals little about the actual training stimulus (Oranchuk et al., 2019).

The core question we are asking is simple: can you produce force here and tolerate it? Depending on the exercise and the individual, this approach can develop force production, muscular activation, positional control, load tolerance, joint control and confidence under load. Crucially, the nervous system is heavily involved throughout this process. Your brain and spinal cord coordinate the recruitment of motor units and regulate the force being produced. We are not simply asking a muscle to work. Instead, we are practising how the body organises and produces force. Resistance training research consistently shows neural adaptations occurring alongside muscular ones, particularly during early strength development (Siddique et al., 2020; Lecce et al., 2026). The tendon is part of this system too. It transmits force from muscle towards bone and responds to mechanical loading in its own right. Systematic reviews of human studies show that chronic loading can alter tendon stiffness and material properties, with the magnitude of loading being a principal factor (Bohm et al., 2015; Lazarczuk et al., 2022). That does not mean doing a single isometric hold instantly strengthens your tendon. Adaptation is far more complex than that. It simply means mechanical loading serves as one of the primary stimuli to which tendon tissues can adapt.

WATCH

Do not just watch the exercise. Notice that the individual produces force without repeatedly moving through the joint (0:42).

Keynote: ISOMETRIC = TOLERATE. We are establishing a foundation of force production and control.

2. ECCENTRIC: Learning to control force while moving

This is where things become more demanding. An eccentric muscle action occurs when a muscle produces force while lengthening. Think about slowly lowering yourself from a squat: you are moving, yet you are not letting gravity take over. Your muscles produce force while controlling the movement. The question then becomes: can you control force while you move? This adds a layer of demand by combining movement, force and control.

Eccentric loading has been studied heavily in rehabilitation, particularly regarding tendon disorders. This is also where some traditional rehabilitation messaging needs correcting. Eccentric exercise is not automatically superior to every other loading strategy. Reviews comparing loading programmes for Achilles and patellar tendinopathy have found that isolated eccentric loading does not consistently outperform other approaches, including combined eccentric-concentric work or heavy slow resistance (Malliaras et al., 2013; Head et al., 2019). That matters. The useful lesson is not that eccentrics are best. Rather, it’s that eccentric loading is one way of asking the body to produce and control force while tissue length changes. That approach can be extremely useful.

Time under tension

One variable we can manipulate during controlled resistance exercise is time under tension. Instead of dropping quickly through a lowering phase, we might deliberately control it over several seconds. However, we must avoid creating another fitness myth, longer is not automatically better. Time under tension is simply one variable among many, sitting alongside load, repetitions, sets, range of motion, contraction type, speed, rest and total training volume. Research shows that repetition duration and tempo can influence the adaptive response, yet they need to be considered as part of the overall training dose rather than treated as a magic number, and very slow tempos are not reliably superior (Burd et al., 2012; Wilk et al., 2021). Therefore, if I ask you to take three seconds to lower something, there is a reason. I am changing the demand and asking you to maintain control for longer.

Deceleration

This reality explains why eccentric work matters well beyond the gym. Your body constantly has to put the brakes on during daily life. Consider tasks like walking downstairs, running downhill, landing, stopping, changing direction, lowering a heavy object or catching yourself when you stumble. The ability to produce force is only half the equation. You’ll also need to absorb and control it.

WATCH

University Hospitals Plymouth NHS Trust physiotherapy videos:

Watch the lowering phase specifically. That controlled descent is the working part of the exercise.

Keynote: ECCENTRIC = CONTROL. We have moved from "can I tolerate force?" to "can I control force while moving?"

3. PLYOMETRIC: Learning to produce and absorb force quickly

This is where rehabilitation starts to look more like the activity you are trying to return to. Plyometric exercise involves rapid force production and absorption, commonly utilising the stretch-shortening cycle.

LOAD → ABSORB → TRANSITION → PRODUCE!

A jump is the obvious example, yet plyometrics are not simply jumping exercises. They are a way of challenging the body to handle higher-velocity movement and rapid transitions between braking and propulsion. Meta-analytic evidence in previously untrained people indicates plyometric training can improve aspects of physical fitness including muscular power and strength. Which is part of why it belongs in the general toolkit rather than being reserved exclusively for athletes (Deng et al., 2024). Also, plyometric work becomes particularly useful later in rehabilitation once capacity and goals require faster movement. It has been described as a vital component of functional recovery. For example, this will be seen through an ACL reconstruction, with progression based on task intensity, movement quality and individual recovery status rather than introducing harder jumps simply because enough time has passed (Buckthorpe & Della Villa, 2021). The question now is: can you produce and absorb force quickly? That is a vastly different question from "can you hold a position?" or "can you slowly control a movement?" Real life is not always slow. You might trip, jump, land, sprint, change direction, catch yourself, step off a kerb, lift something unexpectedly, react to another person or play sport. Your body has to respond and adapt safely.

Nervous System and Plyometrics

The nervous system matters here. As movement becomes faster and more complex, the nervous system has to coordinate force production and movement timing. Resistance training is associated with neural adaptations including changes in voluntary activation and motor-system responses (Siddique et al., 2020). However, we must avoid the internet version of neuroscience. Notably, we are not rewiring your brain every time you perform a squat. The defensible version is that repeated practice and training produce neuromuscular adaptations that influence how the nervous system recruits and coordinates movement. That matters most when the demand becomes fast.

WATCH

For rehabilitation, the important idea is rapid loading, then transition, then force production rather than jumping as high as possible.

Keynote: PLYOMETRIC = REACT. We have moved towards absorbing, producing and redirecting force quickly.

So, what are we actually training?

It is easy to say that we are strengthening your calf (for example), though that is only one part of the whole story. Depending on the exercise, we are influencing a combination of muscle, tendon, joint structures, connective tissue and the nervous system. The contribution of each structure is not identical. We should not pretend that one single exercise trains every tissue in the exact same way. Let look dive deeper into the muscle, tendon, ligament, fascia and the nervus system.

  • Muscle

Muscles produce force. Resistance exercise can change muscular strength and size, with the specific response depending on loading, volume, intensity, exercise selection and training history. However, strength is not just about a bigger muscle. Tt is the ability to produce force when you need it. Therefore, the question is not how strong a muscle is in isolation. It becomes: can this muscle produce the force I need when I need it?

  • Tendon

Tendons transmit force between muscle and bone and possess mechanical properties that shape how the whole muscle-tendon unit behaves. Human studies show tendons adapt to chronic mechanical loading through changes in stiffness and material properties (Bohm et al., 2015; Lazarczuk et al., 2022). Herein is the important distinction. Muscle adaptation and tendon adaptation are not the same thing, rather they do not necessarily occur at the same rate. Feeling stronger does not mean every structure has developed the same capacity, which is one of the primary reasons rehabilitation needs to be progressive.

  • Ligament

Ligaments contribute to passive joint stability and have sensory roles associated with joint position and movement. Ligament rehabilitation is highly specific to the context. For example:

  • Which ligament was injured?

  • What type of injury occurred?

  • Was there surgery involved?

  • Where is the individual in the healing process and what forces are involved?

When looking at research, modern rehabilitation guidelines utilise criterion-based progression involving strength, functional performance and movement quality rather than relying on one specific exercise or simply counting weeks since surgery (van Melick et al., 2016; Brinlee et al., 2022). Consequently, for me, I would never tell a client that a particular exercise strengthens their ligament. That is too simplistic. I would rather explain that we are progressively restoring the capacity of the entire system around the joint.

  • Fascia

Fascia is connective tissue that surrounds and interpenetrates muscles and other structures. Research supports the idea of the role connective tissue has when it contributes to force transmission within the musculoskeletal system. Although, the magnitude and clinical significance of those pathways remain under active investigation (Wilke et al., 2018; Ajimsha et al., 2022). This is where we need to be particularly careful. There is a vast amount of content online suggesting fascia explains almost everything. However, this is also not what the evidence is currently says. Systematic reviews of myofascial chains have found reasonable anatomical evidence for continuity between structures alongside a genuine lack of evidence regarding the functional significance of that continuity (Krause et al., 2016). The defensible concept is simple. The body's connective tissues contribute to mechanical continuity and force transmission. This means the mechanics of movement cannot always be understood by solely looking at one isolated muscle. That said, this is interesting enough without making it magical.

  • Nervous System

Your nervous system helps determine the when, how strongly, how quickly and in what sequence muscles are activated. Resistance training has been associated with neural adaptations involving both cortical and subcortical systems, although the precise mechanisms and their relationship to performance are still being worked out (Siddique et al., 2020; Lecce et al., 2026). As rehabilitation progresses, the demand shifts from "can I activate and hold?" to "can I control?" and finally to "can I react?" This serves as an incredibly useful way of explaining progression without pretending the nervous system is a simple switchboard.

Now, Let Build Even Further!

Load doesn't just mean adding more weight…

This is one of the most important concepts to understand. For me, when I talk about progressive loading, I do not necessarily mean adding another five kilograms to the bar. Load can be changed in many ways:

  • Load: How much external or internal force are you producing?

  • Time: How long are you working for?

  • Time under tension: How long is the tissue producing force during a repetition?

  • Range: How far are you moving?

  • Volume: How many repetitions and sets are you completing?

  • Speed: How quickly are you moving?

  • Velocity: How quickly are you producing or absorbing force?

  • Complexity: How much does your body have to coordinate?

  • Reaction: Do you know what is coming or do you have to respond?

  • Environment: Is the movement predictable or unpredictable?

You can make an exercise harder without adding a single kilogram. Sometimes the most appropriate progression is not more weight at all. It might be more range, better control, greater speed, less predictable movement or eventually greater confidence in your body's ability to handle the task.

Why, Then When, Then How?

This is probably the most important part of the article. For me, I do not want you doing exercises simply because somebody prescribed three sets of ten. Instead, I want you to understand why you are doing them. For instance:

  • Why: What are we trying to improve? Is it strength, load tolerance, movement control, deceleration, power, reaction, confidence or function?

  • When: Is your body ready for that level of demand? Your progression should be informed by your current capacity, symptoms, performance and goals. In return-to-sport rehabilitation especially, evidence-based guidelines explicitly recommend criterion-based progression rather than time alone (van Melick et al., 2016; Meredith et al., 2020).

  • How: What load, what range, what speed and what level of control are required? What should you feel and what should you avoid? What happens afterwards? These questions are crucial to be asking yourself! Also, your response to loading, should matter too.

Rehabilitation isn't always a straight line…

Your rehabilitation might need to broadly move from tolerate, to control, to absorb, to produce, to react and finally to perform. However, your body does not read a textbook. You might be strong but lack confidence. You might have excellent slow control but struggle with speed. You might tolerate heavy resistance but struggle with impact. You might jump forwards comfortably but struggle to change direction. You might move beautifully in a predictable environment yet struggle when something unexpected happens. That does not necessarily mean you have gone backwards. Instead, it reveals something incredibly useful: there is another specific part of your capacity that needs attention. This is why return to sport is better understood as a continuum rather than a single moment when someone suddenly becomes rehabilitated (Meredith et al., 2020).

From rehabilitation back to life…

The exercise isn't the goal. The exercise is the tool. The goal might be walking without restriction, getting back into the gym, running, hiking, lifting your child, returning to work, returning to sport, jumping, changing direction, playing with your kids, or simply moving without constantly worrying about what might happen. That's why I want rehabilitation to make sense to you. You shouldn't just know what you're doing. You should understand why. Because when you understand the reason behind the exercise, you understand what we're trying to change and what progression actually means.

The “Simple” Version!

  • ISOMETRIC = Tolerate: Produce force and hold.
    ECCENTRIC = Control: Produce force while controlling movement as the muscle lengthens.
    PLYOMETRIC = React: Absorb, transition and produce force quickly.

Beneath all three, the muscle, tendon, ligament, fascia and nervous system interact as part of a much larger interconnecting system. Crucially, that system is constantly adapting to the demands we place on it.

That said... your body is not broken!

This is the core message I want people to take away. Your body is not necessarily something that needs to be fixed. It is an adaptable system that responds directly to the demands we place on it. Sometimes those demands have been too much. Sometimes they have been too little. Sometimes an injury temporarily reduces what your body can tolerate and sometimes fear becomes part of the equation. The answer is not always to avoid loading the body. Usually, the answer is to reintroduce the right amount of demand at the right time, in the right way and build progressively from there. For example, rehabilitation might look like:
• Load it
• Control it
• Challenge it
• Progress it
• Trust it again

Your Body Mechanic Advice

This article explains the general principles of exercise loading and rehabilitation. It is not a diagnosis, nor does it take away from such spaces! An individual rehabilitation programme or a substitute for assessment by an appropriately qualified healthcare professional is always more valuable than making assumptions. Also, the appropriate exercise, loading strategy and progression will all depend on:

  • The individual

  • The tissue involved

  • The nature sustained

  • The severity of the injury

  • The healing status

  • The current capacity

  • The symptoms

  • The training history

  • The activity they want to return to

If you have experienced significant trauma, surgery, a suspected significant injury or symptoms you are unsure about. Its self-explanatory, seek clinical assessment before progressing your exercise.

One decisive point worth stating clearly!

An exercise is not good simply because it is difficult. Rather, it is good when it provides an appropriate stimulus for the individual and their specific set of needs. For me, that’s why I do not want rehabilitation to be solely about handing someone a list of exercises and sending them on their way. From my perspective, I want you to understand your own body and its needs. Additionally, it’s in a therapist's best interest for you to be able to comprehend why you are being asked to do these exercises, what we are trying to change and where we are trying to get you to do. Which all needs to be clearly understood and held accounted for, to ensure the best outcome measurements for success. Ultimately, rehabilitation is about becoming capable of doing the things you actually need your body to do for the best outcome you are seeking to achieve. Whatever that might be, it simply cannot be the therapist's problem to solve for you.

 Wayne Armour, Your Body Mechanic

References

Ajimsha, M. S., Shenoy, P. D., Surendran, P. J., Jacob, P., & Bilal, M. J. (2022). Evidence of in-vivo myofascial force transfer in humans: A systematic scoping review. Journal of Bodywork and Movement Therapies, 32, 183–195. https://doi.org/10.1016/j.jbmt.2022.05.006

Bohm, S., Mersmann, F., & Arampatzis, A. (2015). Human tendon adaptation in response to mechanical loading: A systematic review and meta-analysis of exercise intervention studies on healthy adults. Sports Medicine - Open, 1, Article 7. https://doi.org/10.1186/s40798-015-0009-9

Brinlee, A. W., Dickenson, S. B., Hunter-Giordano, A., & Snyder-Mackler, L. (2022). ACL reconstruction rehabilitation: Clinical data, biologic healing, and criterion-based milestones to inform a return-to-sport guideline. Sports Health, 14(5), 770–779. https://doi.org/10.1177/19417381211056873

Buckthorpe, M., & Della Villa, F. (2021). Recommendations for plyometric training after ACL reconstruction: A clinical commentary. International Journal of Sports Physical Therapy, 16(3), 879–895. https://pubmed.ncbi.nlm.nih.gov/34123540/

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Deng, N., Soh, K. G., Abdullah, B. B., Huang, D., Xu, F., Bashir, M., & Zhang, D. (2024). Effects of plyometric training on health-related physical fitness in untrained participants: A systematic review and meta-analysis. Scientific Reports, 14, Article 11272. https://pubmed.ncbi.nlm.nih.gov/38760392/

Head, J., Mallows, A., Debenham, J., Travers, M. J., & Allen, L. (2019). The efficacy of loading programmes for improving patient-reported outcomes in chronic midportion Achilles tendinopathy: A systematic review. Musculoskeletal Care, 17(4), 283–299. https://doi.org/10.1002/msc.1428

Krause, F., Wilke, J., Vogt, L., & Banzer, W. (2016). Intermuscular force transmission along myofascial chains: A systematic review. Journal of Anatomy, 228(6), 910–918. https://doi.org/10.1111/joa.12464

Lazarczuk, S. L., Maniar, N., Opar, D. A., Duhig, S. J., Shield, A., Barrett, R. S., & Bourne, M. N. (2022). Mechanical, material and morphological adaptations of healthy lower limb tendons to mechanical loading: A systematic review and meta-analysis. Sports Medicine, 52(10), 2405–2429. https://doi.org/10.1007/s40279-022-01695-y

Lecce, E., Amoruso, P., Felici, F., & Bazzucchi, I. (2026). Resistance training-induced adaptations in the neuromuscular system: Physiological mechanisms and implications for human performance. The Journal of Physiology, 604(1), 81–115. https://doi.org/10.1113/JP289716

Malliaras, P., Barton, C. J., Reeves, N. D., & Langberg, H. (2013). Achilles and patellar tendinopathy loading programmes: A systematic review comparing clinical outcomes and identifying potential mechanisms for effectiveness. Sports Medicine, 43(4), 267–286. https://pubmed.ncbi.nlm.nih.gov/23494258/

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Oranchuk, D. J., Storey, A. G., Nelson, A. R., & Cronin, J. B. (2019). Isometric training and long-term adaptations: Effects of muscle length, intensity, and intent: A systematic review. Scandinavian Journal of Medicine & Science in Sports, 29(4), 484–503. https://doi.org/10.1111/sms.13375

Siddique, U., Rahman, S., Frazer, A. K., Pearce, A. J., Howatson, G., & Kidgell, D. J. (2020). Determining the sites of neural adaptations to resistance training: A systematic review and meta-analysis. Sports Medicine, 50(6), 1107–1128. https://pubmed.ncbi.nlm.nih.gov/31993949/

Van Melick, N., van Cingel, R. E. H., Brooijmans, F., Neeter, C., van Tienen, T., Hullegie, W., & Nijhuis-van der Sanden, M. W. G. (2016). Evidence-based clinical practice update: Practice guidelines for anterior cruciate ligament rehabilitation based on a systematic review and multidisciplinary consensus. British Journal of Sports Medicine, 50(24), 1506–1515. https://doi.org/10.1136/bjsports-2015-095898

Wilk, M., Zajac, A., & Tufano, J. J. (2021). The influence of movement tempo during resistance training on muscular strength and hypertrophy responses: A review. Sports Medicine, 51(8), 1629–1650. https://doi.org/10.1007/s40279-021-01465-2

Wilke, J., Schleip, R., Yucesoy, C. A., & Banzer, W. (2018). Not merely a protective packing organ? A review of fascia and its force transmission capacity. Journal of Applied Physiology, 124(1), 234–244. https://pubmed.ncbi.nlm.nih.gov/29122963/

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Wayne Armour
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