The Use of NIRS-Moxy in Exercise Selection & Training
My previous post in December of 21’ discussed the new implementation of the NIRS-Moxy device into the testing protocol for Cardinal Metabolic & Performance. I wanted to discuss more of what Moxy is, and the benefits that you can derive from the data pulled from the Moxy monitor. To quote Evan Peikon through his work in exercise physiology & bioenergetics as well as to cite from the work of Kirby & colleagues;
“It has previously been observed that as exercise increases up to a heavy exertion level, or close to a maximal power output, there is a progressive decrease in muscle oxygen saturation to a minimal point or plateau which gives rise to exhaustion. Given this information, and the relationship between oxygen delivery, critical power, and work (W)’ it stands to reason that muscle oxygen saturation can be used as an indicator of proximity to failure.” -Evan Peikon
What Does Moxy Actually Do?
Below I’ve included some screenshots of the use of Moxy on the Vo2 Master metaabolic analysis platform. The two isolated metrics pulled from Moxy are percentage of muscle oxygen saturation (Smo2%) and total hemoglobin (THb).
*In the below graph- Moxy monitor has been placed on the left Vastus lateralis muscle*
We can view this individuals warm-up period, squat set & dead lift with recovery period in between these. The purple line is representing the change in (Smo2) from beginning to the end of the exercise set thereby looking at recovery ability. The red line is representing the total hemoglobin (tHb) in comparison. For the sake of time, and also attention span, I’m going to only discuss the Smo2 trends we see within the two charts. You’ll notice that the red tHb line will increase when Smo2 decreases. Below is an example from the Vo2 Master platform and the PNOE platform is further down. This is a great example to highlight how Moxy is used in resistance or weight training activities.
Points to emphasize
When looking at the lowest points on the graph, represented by the purple lines, you should be able to see three separate groupings. An initial (single) drop at the beginning: (warm-up period). Four drops there in the middle (warm-up set & 3 sets of squats following). And lastly, three drops of Smo2 from 3 dead lift sets. You can clearly see some utilization of Smo2 before the last sets of dead lifts but often this will stem from the loading/unloading of plates in barbell workouts as in the case here.
Warm-Up Period
Resting Smo2 level prior to warm-up (high 60%). I’m looking at the highest point before the first big drop of the purple line.
We see after that initial drop in Smo2, signifying the utilization of oxygen within the muscle site that recovery has now established a new baseline trending upwards until our session of back squats begin.
Back Squats
Utilization: Four clear utilization markers during back squats. When identifying intensity or quality of the lift: Does each exercise set, following the initial warm-up set reach its Smo2 “performance” baseline (where Moxy registers that initial endpoint of Smo2)? We can see the third set does reach it but lifts two & four do not.
Recovery: Understanding and monitoring the utilization of oxygen by the muscle is very important (the large dips we see) but understanding an individuals recovery capacity is equally, if not more important for programming exercise. We can observe this by acknowledging the time, and highest point that the Smo2 (purple line) reaches before the next set begins. I’ve mentioned the “performance baseline” we work off of. Are you able to continuously hit that low point time after time. Recovery is the exact same thing. Is oxygen able to load (be delivered) back into the muscle? Although certainly not a drastic miss, we do see that recovery seems to be getting less and less to our original “recovery baseline” that was established.
Dead Lifts
We move now to dead lifts and assessing the same metrics as previously with the three sets (+ warm-up) of back squats. Again, can be difficult to parse out but we’re looking at those last three large dips before the end of the reading.
How was our utilization of oxygen? Although it seems lifts 2 & 3 hit slightly more of a utilization level, all three are very similar around the mid to high teen%.
How was our recovery? Off the cuff, we can see our recovery metric was well above our previous squat exercises which are around the mid to high 70% range.
Takeaway’s/Future Recommendations
It’s important to emphasize that every person’s makeup regarding exercise tolerance, capacity and ability to produce output is extremely individualized but VERY trainable. This individual during the warm-up phase at the very beginning engaged in one set of single leg squats for each leg. You can clearly see the muscle utilizing oxygen as evident in the drastic drop of Smo2. Did this correlate with their inability to properly recover during the next session of back squats? Altering the warm-up during the next exercise session would be interesting data to collect and analyse.
Exercise protocol & client goals are important to understand and well. This individual had planned and executed the number of lifts they intended to. What if they were wanting to do more? When observing their sets of dead lifts, you could say this individual was certainly able to do another set if they were wanting to do so. As far as the back squat exercise; I would be comfortable allowing them another set if that was something they wanted. I would carefully monitor the muscle utilization and recovery/delivery trend though, through the Smo2 reading. If either metrics failed to reach its set-baseline, I would advise to discontinue the back squat at that time and hit it again the next time this lift was planned. It simply comes down to getting a negative return on your investment and also increasing the chances of injury (2).
Science Break
Let's break down Smo2: Hemoglobin is the molecule in red blood cells that transports the majority of the oxygen in the blood. When oxygen flows through the lungs, hemoglobin binds to it, then releasing it when it passes through the capillaries of the tissue that requires it (3). Myoglobin is a molecule found in muscle cells that has the ability to bind and release oxygen as well as act as an oxygen store (4). The percentages of hemoglobin and myoglobin that carry oxygen are referred to as oxygen saturation. From the time blood leaves the lungs until it reaches the capillaries, oxygen is attached to hemoglobin molecules. The amount of oxygen released from hemoglobin in capillaries is determined by the dissolved oxygen levels in the surrounding environment, as seen by the hemoglobin dissociation curve (5). Moxy, then, is a basic concept that evaluates the supply and demand for oxygen in the tissue surrounding the capillaries. The oxygen saturation will decrease if more oxygen is requested than is given, as indicated by decreased dissolved oxygen levels in the tissue.
Applying the Moxy monitor allows for a true full spectrum look at how the body is functioning from the respiratory system inhaling and exhaling oxygen (O2) & carbon dioxide (Co2), the pulmonary system breaking the oxygen down & regulating airway and blood pressure (6), the cardiac system pumping oxygenated blood, and finally the metabolism of the muscle.
Remember in high school biology, we sat there bored to death listening to the teacher talk about mitochondria? Turns out at least for me, I just needed a different spin on things to make it way more interesting. The health of your mitochondria throughout your body is critical, not only for exercise performance but your entire health overall. Two big points I’m looking at specific to muscle metabolism is its ability to efficiently deliver oxygenated blood to the muscles and then to extract & utilize that oxygen in that specific muscle site.
If all this sounds a little weird, let’s look at a few examples:
“How Would This Relate to Me?”
The real value of Moxy is in seeing how the athlete’s body responds to loads and changes in loads. These assessments allow trainers to identify:
What are the optimum training intensity zones?
Which physiologic systems are limiting performance and which are compensating?
How fast does the athlete recover after load?
What is the athlete’s recovery state from previous workouts?
What is the level of mitochondrial function in the muscle?
Putting Data Into Practice
Intensity - Moxy provides a better indication of an athlete's physiologic training intensity than external measurements such as pace or power since it evaluates the intensity that the body is experiencing rather than just the mechanical output intensity. A runner could be told to run at a rate that keeps their SmO2 level around 65 percent. This could better handle environmental elements like heat and the athlete's level of regeneration than merely running at an 8 minute/mile pace.
Duration - Moxy more properly guides training duration than relying on a fixed time. A weight lifter could keep completing reps until their SmO2 drops below a certain level, then rest. Moxy can thus assist in determining the best number of reps to complete at various stages during a workout.
Recovery - During an exercise, Moxy helps you recover. A hockey player may do an interval training-style drill in which they wait until their SmO2 returns to a specified level after each interval before commencing the next. The interval session may be over if they do not recover to the target level.
Competition
Moxy also improves performance and helps coaches make better decisions during competitions. For example, based on an athlete's actual physiologic characteristics collected in real time, the Moxy device can be used to optimize the pace of a race. It can tell whether an athlete has fatigued to the point where their performance is deteriorating, or when they have recovered sufficiently on the bench to return to the game.
Sport Specific
Endurance Sports
Endurance sports include long-distance cycling, running, and swimming, in which the athlete exerts a sustained effort for several minutes or hours. In relation to endurance sports, Moxy has created a number of assessment techniques. The data from the Moxy device can be used alone or in conjunction with the information or other devices that trainers already have. In endurance sports, Moxy is ideal for guiding intensity and monitoring recovery. Muscle oxygen can be a particularly useful technique for assessing physiologic intensity since it takes into account external elements like temperature and the athlete's recovery condition in a way that external metrics like pace or watts cannot.
Acyclic Sports
Acyclic sports are those in which athletes frequently start and stop, such as soccer, hockey, or football. Athletes in acyclic sports are typically assessed by putting up an all-out effort in drills that are meant to mirror their sport's usual movements. Moxy has the advantage of being able to conduct these assessments while the athlete is on their own field (or court, or pool) and performing their own sport. Linebackers can push sleds, and wide receivers can run patterns in these drills, which are suited to the type of work demanded by the athlete's position or role in a given sport. Trainers can use the assessments to determine which physiologic systems limit performance, allowing them to more accurately track progress in training and assist athletes in learning to recover faster.
Strength Training
Moxy can be utilized as a strength-training assessment tool to establish which fiber system is being loaded. Moxy's SmO2 trends throughout strength training can help determine how the body's systems are adjusting to different loads. Moxy can also be used to help with strength training workout duration and recovery. Monitoring the level of deoxygenation, for example, can be used to calculate the appropriate number of reps, and the recovery time between sets can be optimized based on the level of reoxygenation.
Kirby, B. S., Clark, D. A., Bradley, E. M., & Wilkins, B. W. (2021). The balance of muscle oxygen supply and demand reveals critical metabolic rate and predicts time to exhaustion. Journal of Applied Physiology, 130(6), 1915–1927. https://doi:10.1152/japplphysiol.00058
Lee, E. C., Fragala, M. S., Kavouras, S. A., Queen, R. M., Pryor, J. L., & Casa, D. J. (2017). Biomarkers in Sports and Exercise: Tracking Health, Performance, and Recovery in Athletes. Journal of strength and conditioning research, 31(10), 2920–2937. https://doi.org/10.1519/JSC.0000000000002122
Hsia C.C.W. (2021) Respiratory Function of Hemoglobin: From Origin to Human Physiology and Pathophysiology. In: Magder S., Malhotra A., Hibbert K.A., Hardin C.C. (eds) Cardiopulmonary Monitoring. Springer, Cham. https://doi.org/10.1007/978-3-030-73387-2_40
Hendgen-Cotta, U. B., Kelm, M., & Rassaf, T. (2014). Myoglobin functions in the heart. Free radical biology & medicine, 73, 252–259. https://doi.org/10.1016/j.freeradbiomed.2014.05.005
Gomez-Cambronero J. (2001). THE OXYGEN DISSOCIATION CURVE OF HEMOGLOBIN: BRIDGING THE GAP BETWEEN BIOCHEMISTRY AND PHYSIOLOGY. Journal of chemical education, 78(6), 757. https://doi.org/10.1021/ed078p757
Byrd, J. B., Newby, D. E., Anderson, J. A., Calverley, P., Celli, B. R., Cowans, N. J., Crim, C., Martinez, F. J., Vestbo, J., Yates, J., Brook, R. D., & SUMMIT Investigators (2018). Blood pressure, heart rate, and mortality in chronic obstructive pulmonary disease: the SUMMIT trial. European heart journal, 39(33), 3128–3134. https://doi.org/10.1093/eurheartj/ehy451