As a sports scientist, one of things I love getting to do is taking concepts from research and applying them in practice to see what the outcome is for an individual. If there is a specific problem i’m trying to solve i’ll comb the research for some solutions, then put them to the test and observe the results. Sometimes clear trends emerge through this process and these protocols trickle down into my coaching practice, and other times the observed responses are so variable between individuals that it’s difficult to parse out why something did or didn’t get the desired effect.
Recently i’ve been interested in seeing why some athletes’ lower backs always ‘blow up’ during metcons (even metcons that don’t have a meaningful hinging component) while other athletes almost never experience this. I’ve observed a trend that the Crossfit athletes who have these lower back issues tend to be stronger and more heavily muscle individuals, and often times they’re also the athletes with weak cardiac output who have to regulate their arterial blood pressure through extremity muscle vasoconstriction.
On a quick literature sweep I found a paper titled, “Assessment of lower-back muscle fatigue using electromyography, mechanomyography, and near-infrared spectroscopy”. According to this paper the restriction of blood flow due to high intramuscular mechanical pressure is one of the most important factors in lower back muscle fatigue and that the availability of oxygen in the lower back muscular is strongly linked to muscular endurance capabilities.
In the study they also saw that mechanical pressure drives blood out of the muscle and then blood volume remains low for the remainder of the contraction. This is a compression reaction and it’s something I can easily identify with a Moxy Monitor.
A compression reaction is when muscle tension squeezes blood out of the muscle. This occurs within several seconds of the onset of tension and is diminished upon the release of tension.
So, essentially what is occuring in individuals who suffer from low back ‘pumps’ during Crossfit metcons is that the mechanical pressure on their spinal errectors and stabilizing muscles is creating a scenario where blood is being squeezed out of the muscle at the onset of muscular contraction and steady flow to those tissues is not returning until tension is released. This means that those muscles will be prone to desaturating since oxygen utilization will supercede oxygen delivery. Because metcons typically entail a lot of volume done in a very short period of time this means that the stabilizing muscles in the lower back will not experience complete recovery and as a result fatigue will ensue.
So, I set out to test these theories and see what happens in the spinal erectors of atheltes that do and do not experience issues with their lower backs ‘blowing up’ during metcons. The primary tool I used for this investigation was the Moxy (muscle oxygenation) Monitor. Muscle oxygenation is a measurement of how much hemoglobin is carrying oxygen in the capillaries of the muscle and the subsequent transfer of oxygen to myoglobin, the oxygen carrying molecule located within the muscle. Muscle oxygenation is a localized measure that depends on level of blood flow, and changes in the hemoglobin dissociation curve. Muscle oxygenation is measured optically with NIRS, so it is completely non-invasive.
What does NIRS measure?
“NIRS measurements reflect the balance of O2 delivery to working muscles and muscle O2 consumption in capillary beds” -Ufland et al. 2012
“Combining NIRS with simple physiological interventions, such as venous or arterial occlusions,allows quantitative measurements to be made from skeletal muscle. This provides a tool for assessing two major determinants of the capacity of muscles to exercise: O2 delivery and O2 utilization. The non-invasive nature of NIRS makes it an appealing technique for use in adynamic environment and for activities of daily living.” -Jones et al. 2016
Above you’ll find a sample NIRS trend from the spinal erectors of one of my athletes doing a 60 second long isometric back extension hold on a GHR. This serve as a nice baseline so you can see what a strong contraction in the spinal erectors followed by a relaxation looks like. Notice that upon the start of contraction muscle oxygen saturation (SmO2) drops rapidly then through the contractile period oxygen saturation stays depressed until the contraction ends and SmO2 rebounds. You’ll also notice that upon the start of contraction THb drops rapidly, plateuas at a low level, and then returns to baseline after the end of the contraction. This THb trend represents a compression reaction, which closely matches what was observed in the paper titled, ““Assessment of lower-back muscle fatigue using electromyography, mechanomyography, and near-infrared spectroscopy” that I mentioned earlier. This athlete also reported that they felt a significant lower back pump after this set. Being that this matched the findings from the aforementioned paper I wasn’t too surprised, but this did get me excited to test this out in a metcon.
Below you’ll find a NIRS trends from the spinal erectors of an athlete who struggles with their back ‘blowing up’ during metcons. I had them do the following for time: 30 cal Echo Bike, 20 Deadlifts (225#), 25 Wall Ball (20#).
In the NIRS trend above you’ll see that it’s broken up as three distinct work bouts (the dead lifts and wall balls were completed unbroken) with a short rest in between. During the Echo bike you can see a compression reaction in conjunction with a steady drop in muscle oxygen saturation in the spinal erectors. This reaction shows that high intramuscular mechanical pressure in the spinal erectors is driving blood out of the muscle, and blood volume remains low for the remainder of the contraction. Between the echo bike and dead lift we see blood flow returning to the spinal erectors in conjunction with oxygen being resupplied. Then during the deadlifts we see an initial compression reaction followed by a venous occlusion, which indicates a stronger contraction force where venous outflow from the muscle is restricted. Because arterial blood is still entering the muscle this creates a ‘pooling’ effect in the muscle as well as the feeling of a muscle ‘pump’. At this point the athlete experienced their back ‘blowing up’. Finally, we see that during the wall balls this athlete gets another compression reaction. Note that muscle oxygen saturation stays depressed through both the dealifts and the wall balls, which is associated with muscle fatigue and reduced muscle endurance capabilities. This is a case where the observed response very closely matches what was reported in the literature.
Venous occlusion is when muscle tension restricts the outflow of blood from the muscle. This occurs over tens of seconds to minutes and upon the release of tension blood is able to leave the muscle.
Now that we’ve identified a potential issue the next step will be to assess other athletes that struggle with this problem and then create an intervention to try and address it. While the obvious answer may seem like doing more back extensions, high rep hinging, and so forth that is seldom an effective long term solution for addressing this issue.
In order to determine what protocol is effective for solving a problem, it’s important to understand WHY the problem is occuring in the first place. Part of the way I make sense of coaching is through analogies. This problem reminds me of a lesson that I learned when reading a computer science textbook. In the section on algorithms there was a snippet that read “when we try to find an algoritm to solve out problem we should check that our problem meets the requirements of the algorithm, otherwise the algoritm won’t work.” Because computers cant talk they can’t tell us whether or not we’re selecting an appropriate algoritm. So, if we implement an algoritm it will still executre it’s steps even if it doesn’t make sense to do so and it will produce a nonsense answer. It’s upto the coder to make sure they’re using the right tool for the job. This isn’t disimilar from coaching.
We may be able to see that an athlete’s lower back blows up when they do high rep deadlifts, and as a result we might give them more high rep deadlifts in their training. The athletes is like a computer — they will carry out the ‘algoritm’ whether or not it makes sense to do so, and like the computer they may produce a nonsense answer — in this case, that means not improving what they wanted to improve.
As a coach it’s upto us to make sure they’re using the right tool for the job. One of the great things about technologies like NIRS is that it helps us parse out how tools work and if they’re getting us the desired result.
After identifying athletes that struggle with their lower backs blowing up I tried out a handful of different methods, then I monitored week to week NIRS trens to see if they were accuring the desired adaptations or if we misses the mark. Once I found some protocols that seemed to be working I tried them out on other clients who struggle with the same issues and i’ll observe if I get the correct gross outcome. If the protocol then seems promising i’ll start experimenting with different ways of tweaking it and modifying it with my coaching clients and eventually these protocols trickle down into my coaching mentorship program as well as educational courses I create.
Below i’ve posted a sample concept model to help you determine the causes of lower back muscle fatigue in an individual, as well as how to go about addressing this issue. I’ve also posted some sample protocols that may fall into some of these categories.
Jones S, Chiesa ST, Chaturvedi N, Hughes AD. Recent developments in near-infrared spectroscopy (NIRS) for the assessment of local skeletal muscle microvascular function and
capacity to utilise oxygen. Artery Res. 2016;16:25‐33. doi:10.1016/j.artres.2016.09.001
Ufland P, Lapole T, Ahmaidi S, Buchheit M. Muscle force recovery in relation to muscle oxygenation. Clin Physiol Funct Imaging. 2012;32(5):380‐387. doi:10.1111/j.1475–097X.2012.01141.x
Yoshitake, Yasuhide & Ue, H & Miyazaki, Masami & Moritani, Toshio. (2001). Assessment of lower-back muscle fatigue using electromyography, mechanomyography, and near-infrared spectroscopy. European journal of applied physiology. 84. 174–9. 10.1007/s004210170001.