Improving Oxidative Capacity For Increased Strength, Speed, and Power

In an depth guide to training athletes with oxygen extraction (utilization) limitations

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This newsletter is part four of a four part series. If you haven’t already checked out Understanding Bioenergetic Limitations, Enhancing Oxygen Delivery For Maximal Performance, and Breath To Win- Enhancing Respiratory Muscle Strength And Endurance I recommend you read those before continuing here.

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🧬 What Are Muscle Oxidative Capacity Limitations?

Before discussing training interventions for utilization limited athletes it’s important to acknowledge that the underlying causes of utilization limitations are quite broad, and as a result we cannot have once catch all set of foundational components that need to be addressed for these individuals. For example, a lack of mitochondrial density, a disruption to the normal muscle fiber structure following injury, changes in intramuscular and intermuscular coordination, chronic overtraining, and a left shift in the hemoglobin dissociation curve from hypocapnic breathing can all impair skeletal muscle oxygen extraction.

In order to reconcile this, I suggest we zoom in on mitochondrial density as that will have a meaningful impact on both the magnitude of oxygen extraction, as well as the rate. Additionally, that falls within the sphere of influence of coaches, whereas some of the other contributing factors for utilization limitations are less easily assessed and influenced without bringing other trained professionals into the fold. 

What I find interesting about training utilization limited athletes is how tightly changes in their physiology are linked to improvements in performance. Assuming a utilization limited athlete is not overtrained or injured, the primary adaptations they’ll want to target in their training are increased mitochondrial density, increased enzyme concentrations, improved coordination and recruitment, and increased metabolic oxygen utilization. With a quick internet search, you can look up any of these key terms and find a host of protocols that claim to improve mitochondrial biogenesis.

However,  I’m always skeptical when I see cookie cutter protocols and programs that claim to elicit a highly specific adaptation without any instruction for how to adapt the program to the individual or any inbuilt auto-regulatory components. 

There are plenty of protocols that should elicit a given adaptation in theory. They may even consistently improve performance. However, we don’t always have a reliable way of knowing how and why they lead to performance improvements. As a coach, or athlete, you may not even care why something works, as long as it does work, but there’s a good argument to be made for why you should care.

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🧬 How Can We Ever Truly Know If Our Training Methods Are Working?

At some point you're bound to encounter an athlete who doesn't respond to cookie-cutter training protocols. If you don’t understand what that individual's underlying limitations are and how to target that specific limiter effectively you may be at a loss for how to modify their training. In that scenario you can throw your hands in the air and tell them they’re a non-responder, or you can select another protocol at random and throw darts at the board with a blindfold on. Alternatively, you can use the process of inductive reasoning to come up with an educated guess as to what they need, then follow that hypothesis to its natural conclusion and put it to the test.

A low cost way to better understand the effect of your training methods and how they relate to increases in performance is through basic statistical methods. In the image below we have a tactical athlete’s rate of change of muscle oxygen saturation recorded with a NNOXX One wearable, termed ΔSmO2, plotted against maximum power output on the Echo Bike over a 36-week training period. ΔSmO2 clues us into the balance between oxygen supply and demand — the more negative ΔSmO2 becomes, the greater skeletal muscle oxygen extraction is relative to skeletal muscle oxygen supply. 

When I began coaching the athlete whose data we can observe above, we identified that their maximal rate of oxygen extraction and utilization was a primary limiting factor for increasing their VO2max. Additionally, through speed preservation testing we determined that they needed to improve their maximum sprint speed (MSS) while maintaining their ability to preserve a fixed % of MSS over a set distance. My hypothesis is that these energetic limitations and sport specific limitations had a common cause. In testing we found that this individual's maximum rate of oxygen extraction was 4.5% SmO2 per second and that their maximum sprint speed on the echo bike was 1,315 watts. Over thirty six weeks of training we had them repeat the exact same training protocol and we tracked the highest power output elicited in that session as well as the most negative ΔSmO2 value. In the figure above you can see these data points plotted against one another. 

Over the thirty six week training period we saw a 31% increase in maximum oxygen extraction and a 20% increase in maximum power output. But, the real kicker is that when we calculated the correlation between their ΔSmO2 and maximum power output trends we saw an inverse linear relationship between changes in oxygen extraction and changes in power output. In other words, for every increase in oxygen extraction and utilization we saw a proportional increase in maximum power output. Furthermore, when we calculated the correlation between their training progress on a weekly basis and their increase in power output the correlation coefficient was +0.84. Collectively, these data points give us a strong understanding of how the protocol we used works, how it changes the individual’s underlying physiology, and how it relates to increases in performance.

In order to confirm that these findings extrapolate to a larger population, I then recruited 21 subjects to perform a six week exercise trial where they performed the same repeat desaturation training session weekly and we tracked percent changes in maximum power output and ΔSmO2. You can find the data from that experiment in the figure below, which shows a strong correlation between changes in maximal oxygen extraction and increase in power output such that the individuals with the greater percent change in ΔSmO2 also had the greatest increase in maximal power output.

In another instance I had an athlete who wanted to improve their performance on a 30-second Echo Bike for max calories. After assessing this athlete we determined that they need to improve their maximal power output to get better at this test since they were holding a very high percentage of their maximal sprint speed already.

Additionally, we found this athlete was limited by their rate of oxygen utilization. Over a ten week period we had this athlete complete one developmental U2 training session as well as a 30-second Echo Bike test. In figure eighteen you'll find their five most negative ΔSmO2 values captured during their U2 training sessions plotted against their performance on the 30-second Echo Bike test. Over the ten week training period they consistently hit more negative ΔSmO2 values, and they also improve their score on the Echo Bike test nearly every week.

When calculating the correlation coefficient between ΔSmO2 and performance, I got a value of -0.97. This tells me that the training intervention not only yielded the correct physiological outcome, which is an increase in the rate of maximal oxygen extraction, but also that this physiologic change drove the desired performance outcome. Now imagine that you apply these concepts to the bulk of your training protocols and you have a streamlined system for identifying an individual's limiters — rather than guessing what protocols to use when, you can create a surgical system for spotting and training limitations. 

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🧬 Basic Training Interventions For Utilization Limited Athletes