Preventing Injuries…Fatigue Changes Everything

I’m an assessment guy.  I do a pretty extensive assessment on everyone we train at IFAST.  I do a very broad spectrum of testing because I know that there are few if any definitive tests. I also realize that when it comes to predicting potential injury, anything I do during my controlled assessment will have limited validity in certain situations.

Why?  Because fatigue changes everything.

Fatigue will alter trunk muscle function and therefore balance. (1)

Fatigue alters technique. (2,3)

Fatigue changes landing mechanics and motor control that can result in ACL injuries. (4,5,6)

Fatigue measured as low aerobic power increased risk of injury for rugby players. (7)

Fatigue altered the coordination (acuity) of the entire arm of overhead throwers. (8)

It’s obvious that injuries are the result of multiple factors.  We can never rely on one test or even a battery of tests if they don’t take into consider fatigue and forces similar to those that are experienced in a play situation.

So should we just ignore the whole concept of injury prevention.

No, I don’t think so.  Not by a long shot.

I think the first key concept to address is to train your athletes effectively in the first place by addressing their specific needs and those of their sport. 

Do they have a foundation of general physical preparation to allow them to train at an intensity that will support their performance in game situations?

Do they demonstrate sufficient mobility to perform the required activities without compensation? (Can you identify compensation?)

Do they demonstrate appropriate energy system development for their desired sport?

The next key concept to understand is that everything is an assessment.  It just doesn’t stop when game starts or when the training session begins.

Watch for obvious signs of fatigue (open mouth, heavy breathing, distressed appearance, etc.) and the not so obvious (changes in technique, ability to change direction, signs of instability, etc.).

Give rest when needed (even if it’s not programmed or it’s a crucial point in a game).

Change the training program to adapt to the athletes current reserves.  Nothing is written in stone and your “perfect” program may not be so for every athlete on every day.

We all want our athletes to be successful, and yes, there are times that you must push them harder than they want to be pushed to assure that they are prepared.  However, you must focus on the quality of your athletes’ performance in training or in a game if you’re serious about preventing injuries.
1.  J Sport Rehabil. 2008 Nov;17(4):380-6. 
2.  IEEE Trans Biomed Eng. 2008 Nov;55(11):2666-74.
3.  J Orthop Sports Phys Ther. 2009 Mar;39(3):210-20.
4.  Am J Sports Med. 2008 Mar;36(3):554-65
5.  Med Sci Sports Exerc. 2006 Oct;38(10):1836-42
6.  Am J Sports Med. 2005 Jul;33(7):1022-9
7.  Am J Sports Med. 2005 Mar;33(3):428-34 
8.  J Athl Train. 2007 Jan-Mar;42(1):90-8

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Please note: I reserve the right to delete comments that are offensive or off-topic.

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  • Great post Bill.

    The tough part is convincing some “professionals” out there that you don’t need to run a client in to the ground to get results.

    I guess the same could be said about some of the clients themselves who want to be pushed to the extremes each time.

    I like how you sum it up as “quality of performance”. Definitely a great take home point.

    Dev Chengkalath

  • Bill, you cited some effects of fatigue at the beginning of the post. Having recently re-watched your assessment presentation from last years seminar, I guess its unclear if you’re suggesting it may be smart to test both without and with fatigue??

    Further down the post you mentioned you have to also assess whether the athlete/client has the GPP to perform their sporting actions at an approriate intensity. Does the athlete’s GPP/work capacity play a role in determining how your going to assess (fatigued/not fatigued)?? — basically like if the athlete has poor work capacity, why stretch in a non-fatigued state since they perform most of their training and sporting activity activity in a fatigued state?

    Thanks Bill, its always educational!

  • At IFAST we do assess in both rested and fatigued states whenever possible. If we can observe a client in their competitive environment, it’s even better as we can then identify issues related to work capacity. For instance, alterations in technique and performance when/if the athlete experiences significant fatigue. This combined with energy systems testing gives us a pretty solid background from which to program more specifically.


  • Nice Bill

    This has been my most exhausting year of my life, EVER!

    To go w/your post and a real world example, I strained my low back 2 x as you know, which took a good 6 months to finally alleviate the pain in my glutes, low back and hips – and still the back is problematic

    I also tore my meniscus and will get my 3rd knee surgery

    lack of sleep, w/excess stress has certainly made me the definition of fatigue

    Im looking forward to being healthy again and will keep you posted brother


  • Navjot

    Hello Bill,

    Forgive me if this is the wrong place for this but I have a question that is a bit off topic. I’m currently a physical therapist student whom wants to know what you believe students whom yet to go to pt school, should be focusing on ? Any advice would be great to what makes a great P.T. also. Thanks

  • Lauren

    I just got the shapeshift ebook, and I read your case study on the 106 lb women who was skinny fat. I am like this and have been strength training to fix it and was unsure if I should add cardio to the mix (I want fast results as summer is around the corner). After seeing this, I think I will, but I was concerned with overtraining my legs, especially with the body circuit. I just did that today, and my legs are pretty sore and I’m supposed to do more strength training tomorrow. How can you tell if you are overtraining? I was going to stick with strength training 3x per week plus the body circuits (after strength and on off days) , is this something that is too intense to maintain over a certain amount of time? Also should the circuits/complexes be performed before or after the strength training exercises?

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