Hi there. Welcome to I think to post 76 in this S&C for therapists series. In this post I want to talk about priority of rehabilitation. Something that comes up a lot in my conversations and teachings is the question whether we should focus on hypertrophy or strength first in our rehabilitation efforts.
Hypertrophy, Strength & Body Building
Right, the terms hypertrophy and body building are often used interchangeably on social media and in the ‘BroScience’ type arenas. This isn’t necessarily very helpful when your patient Googles what they’ve heard, especially if they don’t have aspirations to grow some guns in their rehab. Might we also for clarity specify here that strength training and body building are not the same either, which I’m sure you’re very aware.
What’s the aim of hypertrophy training?
Very simply put, it’s to increase the size of the trained musculature. Whilst this is also a remit of body building, within rehabilitation the aim is often focussed on a single limb with a view to restore inter-limb symmetry, or to reverse the atrophy process following injury, surgery or disuse.
Hypertrophy: “…an enlargement of total muscle mass and cross-sectional area, (usually) occurring from hypertrophy of the individual muscle fibres. … During muscle hypertrophy the rate of muscle contractile protein synthesis is greater than decay, leading to greater numbers of actin and myosin filaments in the myofibrils.”
Cifu, 2021. Braddom’s Physical Medicine and Rehabilitation
What’s the aim of strength training?
Here we want to increase the maximal force production capabilities of muscle. For more on muscle strength see here .
Establishing the Priority within Rehab
Okay, back to the question hypertrophy or muscle strength first? What do you think, and importantly why do your think that?
Often, I hear therapists say that it’s important to train hypertrophy first. Why? Well you can actually see the difference compared to the opposite limb. And that’s true, how often have you noticed the rapid atrophy of the musculature of an injured limb, whether that be following casting or just disuse? It happens quickly and this has been demonstrated in the literature, many fold.
For example, following casting a single lower limb of health male participants, Wall et al. (2014) measured quadriceps cross-sectional area (CSA) after its removal. After only 5 days of immobilisation CSA decreased by 3.5%; after 14 days CSA had decreased by to 8.4%. And remember, people aren’t even injured here.
Wall et al (2014). Mean ( SEM) percentage loss of quadriceps cross sectional area (CSA) after 5 (n = 12) or 14 days (n = 12) of one-legged knee immobilization in healthy, young men
Kubo (2010) shows this also in a training-detraining study. For 3 months healthy participants trained isometric knee extensions at 70% MVC (x 10 reps), 4 times per week, they then ceased training for 3 months. Data on muscle strength, CSA (cross-sectional area), EMG (electromyographic activity), and tendinous properties were collected throughout. As we’d expect, the morphological characteristics (CSA, tendon properties) took longer to change by comparison to the neural changes (see table below). This why you don’t see sudden changes in muscle size as you get stronger, it’s principally neurally driven.
But what’s really interesting, is that there was a reversal of change order during detraining; whilst CSA changes were observed at 3-months post training, the CSA had reverted to baseline following 1 month of detraining. You may also note that muscle strength didn’t change over detraining, in effect the neurally-driven training adaptations seemed to have been retained.
Now, this might prompt you to stop reading – got the answer, it’s hypertrophy first! Just hold on though, not all studies show this. I’ve written a few posts on detraining and many studies have shown quite marked changes to strength and power early on in the deconditioning process (see here on power and here on strength). AND, we’ve not really considered the utility of the tissue here. We’re only treating what we can see.
Maximise Tissue Utility
What do I mean by tissue utility? I mean its force producing capabilities. The deconditioning process, especially if associated with injury, pain and disuse, is also associated with quite marked reductions in muscle strength and power.
The Wall et al. (2014) study mentioned above, which casted healthy participants’ legs showed a loss of knee extension strength of 9% following 5 days of casting and a huge 24% loss following 14 days of immobilisation (see below). These changes are greater in magnitude than that seen in muscle CSA.
Wall et al (2014). Mean ( SEM) percentage loss of quadriceps strength after 5 (n = 12) or 14 days (n = 12) of one-legged knee immobilization in healthy, young men.
Many other studies, such as those employing bed rest show this non-uniform loss of muscle strength and CSA. Typically the greatest losses to muscle performance happen in the first few days of disuse, whereas the greatest morphological changes tend to occur a little later (Marusic et al. 2021).
Bigger Muscles Mean More Strength
But I hear you say, larger muscles can produce more force, so we should still focus on CSA first. This is true, there is a relationship between muscle size and strength, with greater muscle CSA being associated with greater force generating capacity. However, the relationship is not a perfect 1.0. This means that not all improvements in force production are explained by an increase in muscle contractile proteins. As we highlighted above, neural changes can explain much of the early changes in force production. Furthermore, the relationship of muscle CSA and strength can vary by sex, training, methods used, training history and age, to name just a few variables (Jones et al. 2012).
Train Hypertrophy or Strength First?
So what’s the answer? Well, how much time do you have and what’s the goal? Yes, we can clearly see muscle atrophy, but this might distract us as we can’t see losses to muscle strength (unless we’re testing it!).
Within a conceptual framework for joint stability muscle strength is an important factor (Minshull, 2021). Chose another population like post ACL reconstruction and we see persistent strength deficits post rehab, which might be a risk factor for increased risk of second injury (Grindem et al. 2021). In the older adult and elderly, reduced strength is associated with joint pain (Muraki et al. 2015), ADL dependence (Wang et al. 2020) and even all cause mortality (Shailendra et al. 2022) and independent of muscle CSA.
Also, consider how much time both you and your patient has to invest in training. If there’s only the opportunity to have a few weeks with someone, especially if they’re novice to resistance training, is it worth focussing on a hypertrophy programme when we know it’ll likely take >6weeks to effect a change (especially in novice trainers) versus optimising the environment for strength adaptation where changes can be achieved in a shorter time?
Strength First
So my answer? I almost always go with a strength first approach. Maximise the utility of the muscular tissue, then if you have the opportunity focus on CSA. Don’t forget there’s potentially a behaviour change piece here as well. If patients haven’t trained like this before and knowing that hypertrophy-type training is all about volume of training (that’s another post), asking a person to engage in a lot of resistance training exercise could be confronting, present too may barriers and then nothing gets done.
References
- Marusic et al. (2021) Nonuniform loss of muscle strength and atrophy during bed rest: a systematic review. J Appl Physiol. 131(1):194-206. [Link]
- Minshull (2021). Conditioning efficacy; a road map for optimizing outcomes in performance-based rehabilitation. Elsevier. [Link]
- Grindem et al. (2016). Simple decision rules can reduce reinjury risk by 84% after ACL reconstruction: the Delaware-Oslo ACL cohort study. Br J Sports Med;50:804–808.
- Wang et al. (2020). Muscle mass, strength, and physical performance predicting activities of daily living: a meta-analysis. J Cachexia Sarcopenia Muscle.;11(1):3-25 [Link]
- Shailendra et al. (2022). Resistance Training and Mortality Risk: A Systematic Review and Meta-Analysis. Am J Preventive Med 63(2):277−285 [Abst]
