In the last year or two, one of the hottest topics in the world of strength of conditioning has been the question of whether or not to include crunches and/or other exercise that includes spinal flexion in training programs. A few experts say “yes”, most these days seem to be saying “no”, but countless articles have been written on the subject and endless discussion has taken place on training forums across the internet.
Those on either side of the debate often cite a long list of reasons why they believe doing crunches and the like is either a back injury waiting to happen and should be avoided at all costs, or why such exercises can and should be used as part of an overall core training program depending on the athlete or individual.
Originally, I planned on writing an article to give my thoughts and opinions on this topic, but the more I looked into the discussion, the more it struck me that such debates and discussions often completely overlook the big picture of injuries to begin with. Doing this not only greatly oversimplifies a vastly complex topic, it fails to give athletes and coaches the right perspective needed to take an intelligent and holistic approach to injury prevention and management.
This is because the truth that you’re not hearing is that what’s being lost amongst endless citation of research, theoretical models of spine function and dogmatic proclamations of which exercises are “good” or “bad” for everyone, is a real understanding of the most important principles of injury prevention and management.
In the real world of performance, injuries are almost always about far more than the inclusion or exclusion of an exercise, or even a particular set of exercises. It would be nice if it was just that simple and if we could solve all the lower back problems of the world by eliminating one particular movement, but unfortunately, the human body is infinitely more multifaceted and dynamic than that.
So, instead of weighing in on whether doing some crunches or sit ups or other similar exercise are like a ticking time bomb that will destroy your back one rep at a time, or if they have their place, I’m going to discuss the bigger picture of injury prevention, treatment and management.
Why Do Injuries Happen?
The best place to get started is to answer the most important question of all, “Why do we get injured to begin with?” After all, if you don’t know why injuries happen, how can you go about doing your best to prevent them?
For the purposes of this discussion, we can break injuries down into two categories: acute and chronic. An acute injury is just like it sounds, a sudden sharp shooting pain that you feel in your hamstring in the middle of a sprint or an elbow that makes a loud popping noise before your arm stops working right, for example. Just about every athlete out there has experienced an acute injury at some point in their training career.
Likewise, most athletes have also experienced a chronic injury at some point as well – perhaps a shoulder that hurts and gets sore after every training session or a low back problem that comes and goes.
Regardless of the type of injury that we’re talking about, the fundamental mechanism that leads to it is one and the same and it’s not what most people think. Rather than the often cited causes – the wrong exercise(s) being used or used too much or not enough of the right exercises used in training – all injuries stem from the same underlying cause: too much stress.
The kind of stress I’m talking about is not the kind most people typically think of, the kind of stress most often associated with the feeling you get when you’ve got a big deadline coming up, a hectic family life, financial struggles, relationship drama, or any other number of issues faced in our daily lives. Instead, the kind of stress I’m talking about is biological stress – some also refer to this as “physiological stress”
While mental stress is something we talk about in terms of a feeling, biological stress is a measure of the physical demands placed on our bodies. Everything from walking around, to typing on a keyboard, to lifting weights and training, all places a measure of biological stress on our body to one degree or another.
This is because a whole lot goes into producing and supporting the production and absorption of muscular force. Our lungs have to get oxygen into our blood, our heart has to pump that blood to our working muscles, the cells in our muscles have to produce the ATP the fibers rely on to contract and relax, our fascia and connective tissue have to provide support and stability, our brain has to carefully orchestrate which muscles produce force and how much force they produce, etc.
This huge myriad of complex biochemical processes all takes place in the blink of and eye and it happens each and every time we do any sort of muscular work. Obviously, the more work we ask of our muscles, i.e. the higher the intensity and volume, the greater the demand placed on all these biological systems necessary to produce force and support movement.
Different types of biological stress
We can break down this demand into two kinds of biological stress: mechanical stress and metabolic stress. Of course the two are always inherently related to one another because metabolism supports muscle function, but mechanical stress is a measure of the force produced and absorbed by the entire neuromuscular skeletal system.
This means it includes everything from the muscle fibers themselves to tendons, ligaments, fascia, bone, etc. All of these tissues are involved in the production and absorption of force and all are placed under mechanical stress any time we put our muscles to work.
Metabolic stress, on the other hand, is a measure of the demand placed on all the tissues involved in energy production – which means it involves pretty much every major system in the body. Tissue in our heart, lungs, vascular network, muscles, brain, etc. all must work together to create the energy our working muscles need so of course the greater mechanical stress we put on our muscles, the greater the metabolic stress as well.
So far, all of this probably seems pretty simple and fairly obvious. Where things start to become much more complex, not to mention interesting, is when we start talking about biological adaptation. It’s the body’s fundamental ability to adapt to the demands placed on it that both keep us alive and set us up for potential injury when its limits are pushed.
You see, it all comes back to the fact that the body isn’t really a big fan of stress in general. The more stress the body is under, the harder it has to work to maintain homeostasis and the greater the stressor – whatever is placing the demands on the body – is perceived as a threat.
In the context of training, the stressor, of course, is in the form of the lifting weights, running, jumping, skill practice, etc. because all these require a ton of muscular work.
In order to try to make sure it doesn’t have to work as hard next time to same stressor is faced, and thus homeostasis is less disrupted, the body responds by making physiological changes to the mechanical and/or metabolic tissues that were stressed. These tissues are made stronger and/or more metabolically efficient and thus they become better equipped to handle the same level of mechanical and/or metabolic stress it previously was faced with.
The adaptive machinery seen in the diagram above is not just what allows us to become bigger, stronger, faster and better conditioned by challenging our bodies through training, it’s what keeps us alive. If we were not designed to adapt to biological stress, we wouldn’t last long in the real world and we certainly wouldn’t be able to improve our performance by practicing our sport, lifting weights, running, etc.
In recent years, one of the most interesting areas of research has been studying the process of adaption in response to training in great detail, down to the molecular level, in fact. What scientists have been diligently trying to unravel is exactly how the body figures out what just what kind of stressor, i.e. what level of mechanical and metabolic stress, it faced and how it then goes about subsequently remodeling the tissue involved.
Unlocking the details to this process of stress, signaling, and tissue remodeling as seen in the diagram below holds the keys to putting together the most effective training programs possible. If we can understand precisely how the body responds to different training methods, i.e. stressors, and how much stress is needed to elicit an adaptation, then we can figure out the best way to put them all together.
For now, however, training is often more a matter of guesswork, intuition and experience than a process of science. When we get things right, fitness and performance improve and all goes well. When we get things wrong, however, we often end up injured.
The Stress-Adaptation Balance
Training can most accurately be described as “the targeted application of stress designed to disrupt homeostasis and put the body’s defense mechanisms at work, remodeling, strengthening and improving the efficiency of many different systems throughout the body.” I know that might sound like a mouthful, but if we look at the process, it’s actually pretty straightforward.
First, we choose the type of stress that we’re going to apply by first selecting the mode of exercise, i.e. practicing our sport, lifting weights, running, swimming, etc. Next, we choose which area or areas of the body that we’re going to target by choosing the exercises we’re going to perform in the training session. Finally, we decide how much stress we’re going to apply by determining the overall volume and intensity.
These simple variables are what define the training session, the mix of mechanical and metabolic stress, where it’s applied in the body, and how much is applied. Of course the goal is always to apply the right type of stress in the correct amount and targeted to the right areas necessary to improve performance.
Of course, even if we’re able to accomplish this goal within the training session, we have to consider that it takes more than a single training session to improve performance and so this process gets repeated over and over again. The training session becomes the training week, the training week becomes the training month, the training month because the training phase, and so on and so on.
What makes this training process infinitely more complex than it may first appear is what happens in between sessions as our body’s respond to the stress of the training session. The complexity stems from how many variables are involved in how we adapt to the stress imposed by training.
Everything from our genetics to our diet, our level of mental stress, our training history, to our sleep all play a huge role in how quickly our tissues are able to rebuild and adapt to the training process. Get enough sleep, eat well, have the right genetics and a long history of training and you’ll respond much quicker and adapt much faster to the same level of stress than someone who is under chronic mental stress, has problems sleeping, a poor diet and lesser genetics Even subtle differences in any one of these many variables can have a dramatic impact on the ability to adapt to a given level of stress.
The Stress-Adaptation Balance
Unfortunately, the importance of all these variables and their ability to dramatically influence how well a person responds and adapts to a training program is often overlooked. Everybody is different and many of these factors change over time. This means that not only is the ability to adapt to stress a highly individual ability, but it’s also quite dynamic as well. This means and that we must always look at both sides of the stress-adaption equation if we want to do an effective job of developing and manage training programs.
Rather than in some particular inclusion or exclusion of exercises, it is this delicate balance between the application of stress and the body’s ability to adapt is where the true difference between improving performance and getting injured lies. Find the right balance and apply the correct amount of stress and you will be rewarded with increased strength, power, conditioning, or whatever physical qualities you are training to develop. Apply more stress than your body can handle over time, however, and decreased performance and injury become an inevitability.
Stress Overload and the Injury Cycle
Although it may be obvious on the surface why placing more stress on your body, either acutely or over time, than it can adapt to can lead to injury, it’s worth a quick discussion on the details.
First, it’s important to understand that when faced with more stress than it can handle, the body takes specific steps designed to preserve homeostasis and minimize the impact of the stressor. Again, this is the body’s defense mechanism at work, doing what it can to keep you alive. While the changes that happen during periods of overstress and overtraining do just that, they also inherently set you up for injury as well.
During the early stages of overtraining – which is really just another name for what happens when we apply too much stress over time –the body attempts to handle this by turning down the peripheral sensitivity to the stress response hormones.
Imagine you’re having a feud with a neighbor and they insist on blasting their stereo so loud that you can hear it throughout your entire house. If you wanted to get some sleep, you’d first make sure all the doors and windows were closed and then put in some ear plugs so the sound would be minimized.
This is basically what the body does when you start imposing too much stress on it, it turns down the response by muting the effects of hormones released when you’re training. During periods of intense stress it can still make sure these hormones do their job, however, by producing more of them than it did before. This would be the same as if your neighbor realized you were wearing earplugs and just turned up the music even louder.
If you insist on working the body too hard despite its attempts to mitigate the stress, it then has no choice but to “turn down the music” completely so to speak. In other words, rather than just turning down tissue sensitivity to the hormones, it decreases production of them entirely. This results in a completely muted stress response and it represents the body’s final efforts to deal with chronic stress using the biological weapons at its disposal.
It is in both of these periods of too much stress that the body’s chances of becoming injured become greatly increased. The reason for this is that maintaining a normal response to stress is vitally important for making sure your muscles, tendons, ligaments, bone, etc. can handle the biomechanical and metabolic stresses of training and performance.
When extremely powerful chemical messengers like adrenaline, noradrenaline, cortisol, growth hormone, testosterone, estrogen, dopamine, etc. are not within the appropriate ranges needed for your neuromuscular system to produce force, bad things can, and often do, happen. Indeed, an entire range of hormones and neurotransmitters can all become altered to levels far above or below norms during periods of overstress and overtraining. Even the immune system becomes compromised and can lead to higher or lower than normal levels of inflammation.
In other words, the body’s attempt to cope with a chronic stress overload inherently put us at greatly increased risk for injury during periods of intense stress such as training and competition. Loads and forces that may not have caused any problems before now may all of a sudden exceed our capacities and next thing we know, we pull a muscle or tear a ligament.
Such events may happen either because tissue becomes less able to produce or absorb force, or because errors in the motor control system may activate muscles at the wrong time. Whichever the case may be – and science can offer few solid answers to such questions at this point – it’s clear that any time the stress response is altered as a result of an imbalance between stress and adaption and we continue to ask our bodies to perform at a high level, we are setting ourselves up for injury and failure.
Even worse, it’s also clear that the single greatest predictor of future injury is the existence of a current or previous injury. This principle too, is the result of the body’s adaptive machinery at work because any time tissue becomes damaged and can’t work correctly, the body will always try to accomplish what’s being asked of it by calling other muscles into action. This is known as compensation and it’s why rolling an ankle or tearing an ACL may lead down the road to low back problems or shoulder problems or any other number of injuries up the chain.
Any time we damage one area, we put the other areas that pick up the slack at risk for injuries because they are often not most well equipped to handle the same level of force as the muscles and supporting tissue that they are compensating for. Over time, this is why we often see acute injuries become chronic and how seemingly unrelated injuries are frequently far more connected than we may realize.
This vicious injury cycle can be seen in the diagram below.
The Injury Cycle
The Bottom Line on Injuries
By now, I hope you’ve gotten the idea that looking at injuries merely from the standpoint of the use or misuse of particular exercises doesn’t paint a very complete picture of why they happen. Even when such discussions extend into the realm of analyzing various movement patterns and joint function while trying to predict or minimize risk of injuries purely through improving quality of movement, they still completely overlook the fundamental importance of the stress-adaptation balance.
Although there is certainly value in assessing the specific stress given exercises may place on particular joints and whether or not they are appropriate given an individuals needs, limitations and goals, focusing the entire discussion in this area often fails to consider the underlying role of stress and tends to lead to a surface level approach to injury prevention based purely on exercise selection rather than on a holistic approach to biological stress management.
The truth that’s missed and rarely discussed is that every athlete and individual truly are different and no two people will ever respond the same to a given training program and level of stress. In recent years, the days of personal training have been replaced with bootcamps, CrossFit, P90x and other such programs that blatantly and blindly encourage anyone and everyone do the same thing.
Not only do such approaches always fail miserably to consider a person’s individual ability to adapt to stress, they often preach that results are a direct result of nothing more than intensity. The “more is always better” approach to training with high intensity coupled with a lack of individualization is a literal injury recipe for disaster and only demonstrates a clearly misguided sales pitch/business model rather than an appreciation and understanding for how the human body works as a whole.
Today’s youth are also under attack from a similar approach as well and this is why it’s become sadly common to see athletes as young as 14 suffering from chronic stress injuries like tendonitis. The multi-sport athlete has been replaced with the club season and private instruction. An endless amount of year round skill practice coupled with a lack of time dedicated to all around physical preparation and athletic development is largely to blame for the huge increase in youth sports injuries in recent years.
Once again, it all comes down to stress and the inability to properly balance stress with adaptation. While some are capable of adapting to far more stress than others, no one is immune from the effects of a poorly designed training program designed to make money rather than produce results and/or an unhealthy lifestyle that only serves to magnify the stress level rather than facilitate recovery and adaption.
Whether you’re an athlete, coach, therapist, doctor, or just train to be healthy and stay in shape, my interest in writing this article was to present you with a more complete view of the injury process than I think is often being presented and discussed. In my opinion and experience, a great many of the injuries that occur today could be prevented with the right approach to training.
Rather than endlessly discuss which exercises are “bad” or which exercises are “good,” it’s time to shift the debate to one based on a much more comprehensive viewpoint and a real understanding of the true nature of stress and injuries. Although this article is really nothing more than an overview of the topic, my sincerest hope is that it makes some people think and starts some discussion along these lines.
Of course, I’ll be expanding greatly on this topic and providing a complete injury prevention, treatment and management plan based on the principles discussed in this article in my new project (read about it here) and even more so in another new project I’ll be announcing shortly. If you haven’t read my book yet, you’ll also find a great deal on the subject of stress and how to design individualized training programs that apply and manage stress effectively.
As always, discussion and feedback is welcome and please feel free to pass this article along to other coaches, athletes, trainers and therapists and anyone else in the training community as well!
Nice work Joel! You may have caught my recent interview with Stuart McGill on my blog at http://www.MyRehabExercise.com/blog. In a follow up conversation we had re: the fall out in the forums on crunch vs. no-crunch, his points came back to what you’re pointing out. In essence, no good or bad exercises, but injury will occur when repetition, volume, intensity are added to a system not ready for it. That unprepped system may be due to imbalances, poor overall training, inadequate recovery, etc. As you point out, the assessment of the INDIVIDUAL athlete’s status on that given day of training is key. I like what you’re doing here Joel!!
Dr. Phillip Snell, Portland, OR
Thanks for the comments, I did get a chance to listen your interview and I like McGill’s work in general, but I”m not sure that I agree with his model of there being some finite number of spinal flexion cycles. I think this concept isn’t in alignment with the principles of adaptation and as I laid out, it comes down to how much stress is applied vs. what the body can adapt to and I’m not sure I see any reason why movements that include spinal flexion within normal ranges of spinal lumbar motion would be any different.
I do like that he mentioned that different people have different shaped spines and I could certainly see that some spines may be better suited towards adapting to the stress of particular movements than others, I’m just not convinced that blanket statements about any joint having some finite number of movement cycles is an accurate way of looking at how the body works.
Great article Joel.
I really like the bit about compensation, something I feel gets overlooked. I experienced this first hand, I tore off my MCL in a BJJ injury and once I rehabbed the knee back to full strength, my back started giving me issues, I’m sure it was down to compromised movement patterns post knee surgery. Its an excellent point to note that past or current injuries can be a predictor for future issues and a lot of things can be headed off at the pass with a bit of awareness and good coaching
Good article, I fully believe that everything that was said is true, but I was wondering if you know of any research backing this?