How to Leverage Technology to Improve Endurance Performance

I recently presented a webinar titled, How to Leverage Technology to Improve Endurance Performance. Below you’ll find a recording of the webinar, as well as a section-by-section written version (for those who prefer written word to video 😊).

🧬 What Is Muscle Oxygenation?

Muscle oxygenation is the percentage of blood in a muscle that is carrying oxygen, and it’s an easy to interpret measurement, reflecting the balance of oxygen supply and demand in the working muscles.

🧬 Basic Muscle Oxygenation Trends and Analysis

When muscle oxygenation is decreasing, it means that oxygen utilization is greater than oxygen supply. Under normal conditions muscle oxygenation declines during high intensity exercise, or at the start of an exercise bout, as you can see in the image above. The harder an athlete works, the more rapidly muscle oxygenation declines and the lower the level it gets down to. Additionally, a normal muscle oxygenation value after an athlete pushes themself to task failure ranges between 10-40%, depending on the individual. 

When muscle oxygenation is steady and unchanging, a metabolic steady state has occurred, which means that oxygen supply and demand in the exercising muscles are balanced. The highest output an athlete can sustain with a stable muscle oxygenation value is called their maximal steady state intensity. 

Finally, when muscle oxygenation increases, it means oxygen supply is greater than oxygen utilization. Under normal circumstances this occurs during low intensity exercise, or during the rest period after exercise, as demonstrated on screen. The fitter an athlete is the faster they will reoxygenate their tissues during rest and a normal peak muscle oxygenation value after exercise is 65-85%. 

🧬 Advanced Muscle Oxygenation Trends and Analysis

In order to gain maximal insights from your muscle oxygenation (SmO2) data, it's important to contextualize it against external measurements of load such as power, speed, or weight. For endurance athletes using a power meter, tracking their speed with GPS, or using indoor exercise machines that track their pace, it's easy to cross-compare NNOXX's muscle oxygenation and nitric oxide measurements with external load data. 

However, there are instances where this is not feasible, such as sports practice where athletes are on the field. NNOXX has solved this problem by embedding accelerometers within its wearable device, allowing it to measure athletes' external load and display this data within its web-based high-performance portal. Now, for the first time, coaches and athletes can perform advanced muscle oxygenation trend analysis no matter the training environment. 

Under normal circumstances muscle oxygen and external load are negatively correlated, which means that as power increases, muscle oxygenation decreases and vice versa. The image above summarizes the expected relationships between muscle oxygenation (SmO2) and external load. However, there are circumstances where the above relationships do not hold, and in these cases the observed data trends provide important clues about an athlete's internal physiologic state.

NNOXX is the first and only device to measure both internal and external measurements of exercise intensity. 

Before moving on I want to quickly emphasize how big a value add being able to measure internal and external load with a single device is. Over the years i’ve used many devices that can measure muscle oxygenation, and the biggest limitation for being able to interpret data is the lack of external load data.

 NNOXX is the first and only device that can measure both muscle oxygenation and acceleration, making it easy to interpret data. For example, in the picture above we have my muscle oxygenation and acceleration data during a warmup, three 1 mile bike intervals, and a sprint. During my warmup you can see muscle oxygenation steadily declining. Since we have my acceleration data, we know that the reason for that is that i’m steadily speeding up across the warm-up period. Towards the end of the workout you can see that I utilize much more oxygen during the sprint than during my bike intervals. Without having external load data we wouldn’t know exactly why this is the case, but with that data we can see my acceleration was ~50% higher, resulting in an additional ~15-20% deoxygenation. 

🧬 What Is Nitric Oxide?

Now that we’ve covered muscle oxygenation in depth, I’ll briefly talk about NNOXX’s nitric oxide measurement and interpretation before discussing targeted use cases for NNOXX One and NNOXX One Elite.

Many endurance athletes are familiar with nitric oxide and its benefits, but most don’t know that there are many different forms of nitric oxide in the body, and the effects of nitric oxide depend on its source. 

“Given that NO contributes directly to blood flow, oxygen delivery, glucose uptake, muscle velocity, power output, and muscle growth; a higher NO level may enhance an athlete’s overall performance and endurance — even among athletes who were already fit and healthy.” -Dr. Rick Cohen, MD

NNOXX specifically measures nitric oxide released from red blood cells, which play an essential role in the respiratory cycle, increasing blood flow and oxygen delivery to tissues.

🧬 Basic Nitric Oxide Trends And Analysis

During intense exercise muscle oxygenation levels decline, since oxygen demand in the muscle’s exceeds oxygen supply. When oxygen levels in the muscle decrease, nitric oxide  is released from red blood cells passing through the muscle’s small blood vessels, signaling the small blood vessels to dilate and increasing muscle blood flow. 

When an athlete rests, muscle oxygenation increases and there is no longer a need for increased blood flow. As a result, nitric oxide levels go back down, as demonstrated in the image above.

This system makes sense when you consider the need to regulate blood flow at the level of individual tissues. When oxygen levels in a tissue are low, nitric oxide is released from the red blood cells, causing the blood vessels to widen, which results in greater blood flow and oxygen delivery. Then when oxygen levels in a tissue are high nitric oxide is not released and blood flow is evenly maintained. Thus, nitric oxide increases and decreases based on a tissue's needs. 

In order to gain maximal insights from your nitric oxide data, it must be contextualized against both muscle oxygenation  and external measurements of load. Under normal circumstances nitric oxide and external load are positively correlated, meaning the harder you work the more NO is released and vice versa.  

🧬 Real-Time Pace Guidance With NNOXX

Traditionally systemic physiological responses such as changes in VO2, heart rate, and blood lactate have been used to quantify exercise intensity and inform athlete’s pacing strategies during training and racing.

However, these approaches all have limitations. Metabolic analyzers are cumbersome and difficult to use, blood lactate measurement are invasive, and heart rate lacks accuracy for guiding intensity. 

An alternative approach is to use local indicators of a working muscle’s status, such as muscle oxygenation, nitric oxide, and muscle oxygen consumption, which can be monitored with a NNOXX wearable device in real-time.

“This [NIRS] 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 a dynamic environment and for activities of daily living.” – Jones et al., 2016

NNOXX’s non-invasive biomarker measurements provide a simple, safe, and reliable way to determine exercise intensity based on changes on the metabolic status of working muscles, which are associated with systemic changes in whole-body metabolism. As a result, athlete’s can use their NNOXX data to adjust their pacing and exertion during training and racing to maximize performance.

🧬 Real-Time Pace Guidance For Beginners

Every athlete has a different minimum and maximum muscle oxygenation value, which they can learn from experience. For example, my resting muscle oxygenation level ranges from 60-70%, and my minum muscle oxygenation level during maximal effort exercise gets as low as 20-30%.

 In addition to learning their own minimum and maximum muscle oxygenation values, athlete’s can learn to identify what ranges of values are easy or challenging for them to maintain, which can be used as a real-time feedback tool to guide exercise intensity.

Once an athlete intuitively understands how different muscle oxygenation values relate to their level of exertion and fatigue, they can begin to associate different bodily sensations with their data trends. For example, when my muscle oxygenation goes below 55%, my breathing begins to elevate, but I can still hold a conversation and sustain that output indefinitely.

However, when my muscle oxygen is between is between 40-50%, I’m breathing heavy and feel a mild burning sensation in my muscles. This level of exertion is comfortably challenging, and I can sustain it for an extended duration if needed. 

Once my muscle oxygenation is between 30-40%, my breathing becomes labored and my muscles have an uncomfortable continuous burning sensation. This exertion level is unsustainable and i have a limited amount of time I can spend here before fatigue mounts. 

Finally, when my muscle oxygenation is below 30% I can no longer coordinate my breathing, and my muscles rapidly fatigue. Often, i’ll see my SmO2 in this range if i’m climbing aggressively on my bike. Since I know the time I can spend below 30% SmO2 is limited, I use this as a sign to reduce my power to avoid spilling over to such a degree that I can’t recover. 

🧬 Real-Time Pace Guidance For Intermediates

To make the most of monitoring muscle oxygenation for real-time pace guidance, it’s important to also monitor your power or speed as well, which can be done with a power meter, or GPS-enabled mobile phone or smart watch. 

Under normal circumstances muscle oxygen and external load are negatively correlated, which means that as power increases, muscle oxygenation decreases and vice versa. The image on summarizes the expected relationships between muscle oxygenation (SmO2) and power.

However, there are circumstances where these relationships don’t hold up, and in these cases the observed data trends provide important clues about an athlete's internal physiologic state. There are instances where an athlete is holding a stable power output muscle oxygenation, then suddenly their muscle oxygenation level begins to climb upwards. This is an indicator that the athlete is changing their muscle recruitment pattern, which could be intentional or unintentional. For example, let’s say I'm biking at 300 watts and an SmO2 level of 40% and my outer quadriceps are starting to feel fatigued. I may decide to use my hamstrings to pull on the pedals more, which will reduce the load on my quadriceps muscles, resulting in a slight increase in their SmO2 level. 

There are also cases where an athlete is holding a stable power output and muscle oxygenation, then suddenly their SmO2 level begins to gradually decrease This means that the athlete’s muscles are having to work harder to maintain their power output, and is an indicator of increased fatigue. For example, let’s say I’m biking at 300 watts and 35% muscle oxygenation, but after forty minutes my respiratory muscles start to fatigue and I can no longer supply oxygen to my working muscles at as fast a rate. In this case, my oxygen consumption in the working muscles would begin to supersede my oxygen supply, resulting in a progressive SmO2 level as I fatigue. 

Like I mentioned earlier, it’s important to build awareness around your own normal muscle oxygenation and power output levels. For example, you should know your minimum and maximum SmO2 levels, as well as your normal SmO2 ranges during easy, moderate, and hard exercise intensity boutsYou should also have an understanding on your maximal power output level in your selected exercise modality.

With this information, you can begin to build awareness around the relationship between your power output and muscle oxygenation levels, and these relationships change over time as you get fitter  or how they change within a workout as you fatigue.

Through trial and error, you can learn to manipulate your muscle oxygenation level during exercise by altering your power or pace, cadence, breathing volume and frequency, and body position. For example, let’s say you’re on a long training ride and you’re aiming to keep your muscle oxygenation within a certain range. You could try adjusting your gears and cadence to see if you can increase your power without impacting your muscle oxygenation, or you could try experimenting with different breathing strategies, altering your respiratory frequency and tidal volume. 

🧬 Performing Physiologically Guided Training

The next way that you can leverage technology to improve your endurance is by performing physiologically guided workouts. 

One of the biggest mistakes coaches and athletes make is conflating internal and external workloads. For example, let’s say I run a 5:00 mile today, then again next week. My external workload in both cases is identical since I covered the same distance in the same time, but I may experience different degrees of physiological stress during these two workouts and as a result my internal load would be different. 

“While external load provides information about the work completed and the athlete's performance capacity, internal load is the trigger of training-induced adaptations. The daily monitoring of internal load can help identify recovery needs, predict performance decrements, and adjust training and competition programs.” -Francis Gazzano

This same concept applies within a workout as well. For example, I can run 400m repeats on the track at a fixed pace, but that doesn’t mean my body will experience the same metabolic response on each of those intervals, and as a result It’s difficult to know exactly what adaptation i’m getting from the workout. To truly individualize exercise with precision, you need real-time physiological and performance data. 

With NNOXX, I can do my workout and stream my biomarker data in real time, allowing me to auto-regulate my training and make off-the-cuff decisions about my intensity, volume, and recovery.  For example, let’s say I want to do maximal steady state intervals. In this case, I’d self select the highest power output I can hold each set while keeping my muscle oxygenation level stable, which can easily be accomplished using the NNOXX mobile app. I may even find that the appropriate power output not only changes from set to set, but can change within a given work set. 

Or, let’s say I just want to do an easy recovery session. Generally, athletes will use heart rate as guidance during easy sessions, assuming that a low heart rate below 140 BPM means they are doing recovery work. However, that’s not always the case. I’ve seen athletes meaningfully deoxygenate their muscles, even while biking at 120 BPM. What might be a low-intensity training stimulus for one individual may not be for someone else. Just as we individualize hard developmental training, we should also individualize recovery sessions.

🧬 Tracking Changes In Physiology and Fitness

In addition to guiding your training in real-time, NNOXX allows you to perform comprehensive post-hoc data analysis, using our web-based high performance platform. Anytime NNOXX One elite users collect data in real-time using NNOXX’s mobile app, it will automatically appear in their account in our online portal, making it easy to analyze and extract insights. 

By collecting data regularly, in real world-environments, you can get a more  complete picture of your performance and how it changes over time. Continuous data collection also allows you to discover unique athlete performance fingerprints, which is how an individual responds to a given exercise stressor. Identifying an athlete’s performance fingerprint allows them to see how they are adapting to their training week to week, in turn allowing them to more effectively manage their training program. 

There are two ways you can use NNOXX to track changes in physiology and fitness over time. First, you can perform physiologically guided training and see how their performance changes week to week. 

For example, in the image above we have an athlete’s data from two different days where they performed bike intervals at 30-40% SmO2. The first week they used 325 watts, and the second week they were able to use 350 watts while staging in that muscle oxygenation range. The ability to hold a higher power output at a given muscle oxygenation level indicates improved fitness. 

Second, you can perform performance guided training and see how physiology changes week to week. For example, the image on bottom shows an athlete’s muscle oxygenation data while performing a bike interval at 300 watts on two different weeks. The first week the athlete’s muscle oxygenation at this power output it 300 watts, and the second week their muscle oxygenation is closer to 50%. Being able to do the same workout at a higher muscle oxygenation level is an indicator of improved efficiency and fitness.

🧬 Identifying Physiological Limitations

Finally, the last major use case for endurance athletes is to identify physiological limitations, which are defined as rate limiting factors for increasing an athletes’ VO2max. 

“Physiological testing provides a here-and-now picture of how an athlete’s body is responding to training, which is monitored over time. ‘Quicker race times only tell part of the story. Physiological testing shows the athlete and their coach why they have improved.”– Paul Hough, Lead sport scientist, St Mary’s University

NNOXX users can easily identify their physiological limitations to determine which form of training is best for them. This is a whole topic in and of itself, so rather than fleshing it out here i’ll save this for a future newsletter if it’s a topic of interest (let me know in the comments below).

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