The Rotator Cuff… Too fatigue or not too fatigue?

So the final blog for 2014, and I take a quick look at the question of should we be asking our patients with shoulder issues to exercise their rotator cuffs to fatigue. Enjoy and have a Happy New Year
This debate was triggered after I had a discussion around an old blog of Mike Reinold’s here. Now I really like Mike’s work and have a lot of respect and time for what he has to say. Mikes an incredibly smart guy, has a wealth of knowledge and experience, and does some great work on his website and has produced some interesting research. However, in this blog he argues that you should ‘never’ exercise the rotator cuff to fatigue, and when I questioned him on it recently he still stands by this statement.

I disagree

I actually think the exact opposite. The cuff needs to be worked to fatigue, or very close to fatigue when its in rehab or recovery from injury! Let me explain why…

First I simply disagree with Mike’s use of the word NEVER. One thing I have learned over these last few years is nothing is absolute and there are always exceptions to EVERY rule.
However, semantics aside, I believe exercising to, or very close to fatigue is far superior for developing, strength, endurance, and hypertrophy. There is however, some conflict in the S&C research on this topic with some studies showing fatigue is not always essential. However in general there is a trend for most studies to show that exercising to fatigue is superior for strengthening gains. For more on this see Chris Beardsley review here, and regardless of the research you just don’t argue with the Austrain Oak…

The last three or four reps is what makes the muscle grow. This area of pain divides the champion from someone else who is not a champion. That’s what most people lack, having the guts to go on and just say they’ll go through the pain no matter what happens.Arnold Schwarzenegger

Now exercising to fatigue in the injury rehab world is a little bit different than what Arnold was referring to during bodybuilding, with it having different goals and different priorities! But I aruge that exercising to fatigue is vitally important for any muscle/tendon lacking strength or endurance, and the rotator cuff certainly experiences its fair share of these problems.
In Mike’s blog he uses a study here done in 2008 to support his reasoning of never fatiguing a rotator cuff. They measured the humeral head movement in 20 males with normal healthy shoulders before and after a fatiguing exercise. They found that when they fatigued the cuff, the sub acromial space was reduced significantly when elevating the arm. They attribute this to the cuff being unable to control the humeral head against the upward force of the deltoid allowing an increase in its upward translation. This could potentially mean for those already with sub acromial issues that fatiguing cuff exercises could cause further compression, impingement and therefore pain.
However, there are a couple of major flaws with this study, and so issues when using it to support a belief that we can not exercise the cuff to fatigue. The first and most obvious limitation is that this study was only conducted on healthy males, so we can’t reliably say if the same things happen in those with shoulder pain or with cuff pathology, or even females? It probably does as some other studies have shown that when the cuff is artificially inhibited humeral head translation does increase significantly (ref, ref, ref)

So what!

The next question we have to ask is, so what if the humeral head moves up more! Does this matter? 
For example there are many studies that show that humeral head superior translation is perfectly normal, and highly variable from person to person! Some studies have shown that in normal pain free subjects the humeral head can move up to 12mm off the centre of the glenoid (ref).
Next, are we really that surprised when the cuff is fatigued it doesnt do its job well? This study used by Mike found on average an extra 0.79mm humeral head movement after fatigue, which in context of how much the humeral head can move for some, I really don’t think its that much to worry about.
We also know that many people have torn and deficient rotator cuffs with no pain or issues (ref, ref). Do they have more or less superior humeral head translation than those that have pain? Well, we simply don’t know, but I’d hazard a guess its more.
So can we say increased humeral head translation is solely to blame for sub acromial issues and shoulder pain? Of course we cant! There are many other factors that contribute to sub acromial pain, occupation, BMI, genetics etc etc its not just about the mechanical compressive forces, maybe even they may have little to do with it at all (ref ref)
So why are we so focused and concerned about the mechanical compression, and not all the other factors? Why should we worry about possibly creating a little more excessive humeral head movement, and ignore the many other more positive effects exercising to fatigue has?

Other flaws

This study also choose to fatigue the cuff with an exercise that in my opinion doesn’t represent what most therapists use or consider as a cuff exercise. In fact this exercise, the prone horizontal raise (shown above) heavily targets other key shoulder and scapula muscles such as the Deltoid, Rhomboids and Trapezius.
So how can the researchers differentiate fatigue of the cuff causing humeral head translation, to fatigue of the other scapula muscles causing the cuff to reduce its activity or maybe leading to more scapula downward rotation or altering scapulo-humeral kinematics that could also reduce the sub acromial space?
The simple answer is, they can’t.
However, the biggest flaw in this study is they only observed this extra humeral head movement for only 30 seconds AFTER fatigue!
This means we only know this increased humeral head movement occurs briefly after fatiguing exercise. Why they didn’t look at it for longer, checking humeral head translation at regular time intervals to see when it returned to normal is beyond me. This would have been so much more useful, knowing when the cuff recovers after fatiguing exercise to restore humeral head control.
This I very much suspect would have been after a shortish rest period, I’d guess around 2-5 minutes.

Making sense

Yes, of course it makes sense that when the cuff is fatigued it will be unable to stabilise the humeral head, just like when you have performed squats to fatigue, you cant walk for a while. However, this is only a temporary effect, all muscles when exercised to fatigue don’t function well for a short period of time.
However, that doesn’t mean the exercise induced discomfort of exercising to fatigue will go quickly! It may still ache for quite a while longer, maybe a few days after, which Mike suggested in our brief conversation means the humeral head is still being poorly controlled. But there is no evidence of that. I would simply suggest that this post exercise soreness, this being nothing more than some temporary increase in interstitial tissue oedema increasing the tendon thickness and so maybe increasing pressure in the sub acromial space (ref). This maybe an issue as it could increase the compressive forces on the tendon, but it could also be perfectly fine. 
Yes ok exercising to fatigue hurts, that doesn’t automatically mean its harmful or dangerous.

And what does exercising to fatigue really mean?

For most its a perception or feeling of not being able to do any more exercise, but that doesn’t mean the musclotendinous unit has truly worked to its maximal capacity.
The bit of reading I have done around the subject of fatigue is that the central neural system will always stop the body from exercising to the point of damage by giving signals of distress and discomfort long before actual adverse structural or biochemical harm is done (ref). It seems to take years of training to over ride this neural safety switch, sometimes referred to as the ‘central governor’ to reach true fatigue, most of us mere mortals stop well before!

Positives

Exercising to ‘perceived’ fatigue over multiple sets has a host of positives that in my opinion far outweigh any negatives.
Exercising to fatigue although as I mentioned has some controversy around it, is well known and well accepted by most to produce significant stimulus needed for increases in musculotendionous strength and endurance, and has research and literature to support it, check PubMed if you don’t believe me (hey its New Years eve give me a break).
Exercising to fatigue is also known to produce many beneficial therapeutic effects for myotendinous problems as well as producing pain relieving analgesic effects, again check PubMed if you don’t trust me…

Recognising when it is best to fatigue the rotator cuff is better than NEVER doing it.

For example you simply wouldn’t fatigue the cuff just prior to going swimming, or playing tennis, nor would you fatigue the cuff before going to the gym to throw some iron around! You also wouldn’t fatigue your cuff first thing in the morning when you need it to work during the rest of the day, especially if you have a manual or over head job, this is all common sense.
How you choose to fatigue the cuff, which exercise you choose, how much load to use, the amount of sets and reps depends on a whole host of other variables and really is for another blog or even for you to ask on one of my courses, shameless plug right here.

Summary

So I hope I have made my case that you can exercise a rotator cuff to fatigue!
In my opinion, mediocre, half arsed exercises, have never helped anyone or anything, especially in a rehab setting.
Now, of course there will be exceptions, as I said at the beginning, exercising to fatigue isn’t suitable for all. Also exercising to fatigue doesn’t suddenly mean you can start being all ‘gung ho’ or hardcore and macho with your patients with a “go hard or go home bro” attitude.
It simply means using your judgement, clinical reasoning and most importantly your exercise physiology knowledge to get the most out of any exercise, and that more often than not means working them to or very close to fatigue, and the rotator cuff is no exception.
As always thanks for reading
Heres to a healthy, happy 2015 to you all
Cheers
Adam