By Carl Valle
Most coaches who ask me what is the hardest quality to develop in team sports are surprised that I say it’s developing aerobic capacity without compromising speed. With talented athletes being faster and more skilled, the days of pure workhorses are long gone. As this summer’s World Cup taught us, players are not slowing down or running less than before, so the new normal is fit and fast.
I have shared countless articles on ways coaches can monitor conditioning and design better aerobic workouts, and I even wrote a blueprint on repeated sprint ability. This article is straightforward: how to evaluate athletes coming in and out of your program with testing and by modeling training. It doesn’t matter if you are a team coach, a strength coach, or an athlete, some aerobic capacity is needed to thrive during the season, not just to finish a game strong.
If you are not targeting the aerobic system with laser precision, it’s likely you are missing out on maximizing improvement in your sport or your athlete’s sport. While this article is mainly for team sports, endurance sports can benefit from a few advancements in the science.
What Is NIRS and Why Should Coaches Care?
You are probably reading this article because the popularity of monitoring local muscle groups is at a tipping point and you want to know if it’s worth trying with your own athletes. Shining light through a muscle can collect specific physiological data effectively, but revealing true insight from monitoring oxygen in a specific muscle sounds like it’s more trouble than it’s worth. NIRS stands for near-infrared spectroscopy, the technique of using light to measure changes in nature, and in this case, biological tissue for sports performance and sports medicine. For decades, the evolution of athlete bioenergetics progressed slowly thanks to non-invasive methods like heart rate telemetry and now NIRS.
In 2014, I wrote about NIRS, and specifically the Moxy Monitor, in sports performance, and today we are seeing more research on muscle oxygen saturation in sports medicine and sports nutrition. Some coaches got on the bandwagon shortly after that article was published, and while I knew about NIRS back in 2010, I didn’t feel that it was ready for prime time then. Therefore, I waited a full eight years before recommending it as standard for coaches today. It’s not that the science wasn’t useful or valid, it’s that the technology just wasn’t ready for the average coach.
If you were to ask the average coach about NIRS or muscle oxygenation, they likely would not be able to articulate how those values connect to workouts. The reason for much of this lack of awareness of muscle oxygenation science is that most of the research on athlete conditioning focuses only on lactate testing and heart rate monitoring. As of today, the bulk of the research still looks to cardiology of the heart and invasive biomarkers for data collection, but expect this to change soon.NIRS is shifting the paradigm from heart rate and acidosis measures to non-invasive methods. Click To Tweet
Coaches should be very interested in NIRS because the paradigm is shifting from heart rate and acidosis measures to non-invasive methods. It’s not that lactate testing or heart rate monitoring is inappropriate or dying off, it’s just that muscle oxygenation has independent value. NIRS does not add another “flavor of the week” metric; the system can answer questions that most coaches would be foolish to guess at. To cut to the chase, NIRS answers the following questions.
Medical: Return-to-play programs can tell if the training is appropriate and aggressive, without risking reinjury.
Performance: Coaches can observe the conditioning trends of local muscle groups instead of systemic global changes. More importantly, coaches can discover which physiological system is holding their athletes back from improvement.
Nutrition: Researchers and dietitians can explore how nutrition interacts with vasodilation, and other health and performance effects of food and supplements.
Recovery: Professionals, whether coaches or even sport scientists, can see how modalities and training facilitate recovery or if the restoration application is invalid.
Obviously, there are other reasons that sports staff would use NIRS with athletes, but for the most part, these four demands in four categories are great examples that illustrate the potential of the technology. Frankly, my main interest is to give confidence to anyone guessing at what is happening to a muscle group or body and reveal direct objective information.
What Is the Moxy Monitor?
As you can guess, the Moxy Monitor is a NIRS device that measures muscle oxygen levels during training. The Moxy unit is wearable, connects wirelessly to a smart device such as a tablet, and includes software for analysis. In addition to the native software included by the company, other developers have extended the software selection for added value analysis. A few consumer products have come and gone, but Moxy succeeds because it’s credible for the experienced coach but still consumer-friendly for individual athletes. You can attach one sensor alone, but many power users connect multiple sensors to compare injured to non-injured muscles, different muscles that are stressed, or the changes to muscle groups that are not heavily used during the exercise.Moxy is credible for the experienced coach but still consumer-friendly for the individual athlete. Click To Tweet
Most of the confusion over the Moxy Monitor can be cleared by explaining what and how the system measures. The Moxy Monitor is exactly what the product name sounds like: muscle oxygenation, hence “Moxy.” The product measures by using near-infrared light through the skin and detecting part of the light after it has travelled into the muscle fiber and returned to the surface and back into the sensor.
Visible and infrared light can travel through biological tissues, and the red and near-infrared regions of the spectrum are useful for instrumentation. As light moves through muscle, fat, and skin, it scatters and identifies oxygenated and deoxygenated blood cells. Like veins and arteries having illusionary colors of blue and red, light can help identify the precise physiological status of regions of superficial muscles. By extracting that light data, coaches can really get insight into what is going on during training. However, like anything, it requires education and a good plan to use the data after it’s collected.
Readings require a process of algorithm development because of sweat, the amount of body fat, and other real life factors. Creating these calculations involves a lot of hard work by the companies that make NIRS sensors. Still, enough data quality exists with the NIRS market that they are useful to coaches for collecting valuable information in the wild. Therefore, trust that if you invest a little extra time, the information collected represents what is happening below the skin’s surface.
Why You Should Measure Local Muscle Oxygenation
It’s perfectly reasonable to stick with a stopwatch and notebook of workouts and not bother with any measuring or monitoring of training. The human body is very compliant and is marvelous at adapting to different training programs. Unfortunately, an athlete is mortal, and some workouts may either cause injury or ruin a career. If you want direct answers to training, you need to assess what is holding an athlete back.
If I was to rename this article, I would use the term “unlocking” in the title, as the goal of the Moxy Monitor is to help solve the mysteries of conditioning. It’s not that we don’t know how the body works—we already have a good idea—it’s that we don’t know precisely how each athlete can improve when they are approaching their genetic ceiling.The goal of the Moxy Monitor is to help solve the mysteries of conditioning. Click To Tweet
When the rubber hits the road, physiologically speaking, working muscles are the limiting factor to conditioning. Simply put, not enough oxygen comes into the muscle at the work rate required to win; hence, the need to improve the efficiency or the ability to transport more oxygen. Our bodies naturally have adaptable organ systems that can accommodate stress by improving their function, but the finite details are guesswork unless you know the exact state of development. Talented athletes will always make pen and paper workouts look elegant and brilliant, but those athletes who slip through the cracks or those seasons when an athlete is not at their best are the reasons the Moxy is useful. Leave no results to chance, as a season can make or break an athlete’s career.
The intersection of biomechanics and exercise physiology is where the value of Moxy lies. Based on sport science feedback and my own experience, the strength of NIRS is measuring muscle oxygenation. Besides cardiorespiratory or heart rate training, Moxy directly and ecologically targets specific muscle groups and movement patterns. Heart rate is great, and doing gas exchange testing is useful for extreme endurance athletes, but performing a VO2 max test for a basketball player isn’t very helpful. Lactate testing is very relevant and useful, but the difference between blood sampling and local muscle testing is that the first is a global representation versus a local phenomenon.
A muscle doesn’t represent an entire body, but has enough value to make choices that are actionable. Click To Tweet
An easy way to look at Moxy is that it’s continuous like a heart rate monitor, more anatomically specific than lactate testing, and more connected to mitochondrial changes than gas exchange testing. It’s not that the other measures aren’t valuable—science supports their inclusion—it’s just that coaches need a useful way to know how muscles respond to training immediately and chronically. One muscle does not represent an entire body, but it does have enough value to make choices that are actionable.
Is NIRS Scientifically Valid for Sports Monitoring?
The most important question with sport technology is validity, or having the device properly measure what it’s supposed to measure. It’s also common for the coach or professional to interpret the data to get a proxy of what is going on physiologically. The most straightforward need of coaches is that the test data represents what goes on during training or testing. The level of accuracy and reliability with the device is also important, but all the data quality answers start with the question of the device being valid in the first place. NIRS is non-invasive, so while it’s convenient, it’s an indirect measure to begin with. However, it is sophisticated enough to be right up there with a gold standard measurement.
Most coaches are going to be unaware of Moxy and NIRS evaluation; the equipment has a long history, so while it’s new to sport, it’s not new to science and medical technology. In the early 2000s, the technology hit an inflection point with sports training and sports medicine. The benefit of the equipment is that there has been enough time to refine the algorithms, and the software and hardware. NIRS devices have been tested in the past in underwater environments, in the heat, on cyclists or cycling training, on team sport athletes such as rugby, and even after eccentric exercises.
One area that seems to be problematic is motion artifacts with high-velocity limb motions and capturing a NIRS reading. Based on the research, it makes sense to use a very firm attachment process or the Moxy can fail to capture data at higher efforts. We learned from motion capture and EMG with sprint studies in the 1970s and 1980s that the timeless challenge of placing wearables on a body moving at high speeds isn’t easy for any company to solve. Still, running fast in conditioning tests is much different than sprinting a 100m. The core issue is not the device or body signal; it’s simply ensuring the device is secure enough for a great reading without creating occlusion from being too tight.
Starting out, the use of NIRS is valid and reliable for specific tests and metrics, and it’s been evaluated in sport and sports medicine for years. Specifically, the MOXY Monitor was evaluated and found to be perfectly acceptable in applied settings. Recently, I reviewed the Moxy Monitor comparison study on Science for Sport, as it was compared to a higher-priced research product and the investigation concluded it was appropriate for sports performance. Also important from the research findings was that both systems reported slightly different data. At the end of the day, coaches need to know that NIRS is a sound measurement option, and that Moxy, as a specific device, collects data that they can use for decisions relevant to basic measures.At the end of the day, coaches need to know that NIRS is a sound measurement option. Click To Tweet
The verdict is a little cloudy with NIRS and what its limitations are, but if simple bike routines with COPD patients utilizing the technology are common, it’s a logical conclusion that the data is useful for the scientific community.
What Are Good Tests for Monitoring?
I can list the best tests to use the Moxy Monitor for or share the best approach in using the technology. Generally, if the test is a good indication of athlete conditioning, adding a Moxy Monitor gives even more value and could be the essential piece to solving complex problems. It’s fine to keep things as simple as possible in training, but make sure it’s honest. I would rather put most of my time into methodology than cookie-cutter protocols, but both examples of testing and methodology are likely appropriate for professionals.
Without distilling testing into a binary approach, field tests and laboratory tests are typically the paths for collecting data. It’s expected that the field testing approach is limited but convenient, and lab testing is the gold standard but not practical. Researchers understand the limitations of lab testing because those investigations may get answers, but they don’t help coaches manage, monitor, or train very well. For the most part, coaches want to improve their field tests so that the tests are more precise and accurate. Sport scientists, stuck between the research demands and applied setting, look for the right compromise or elimination of friction or barriers that impair data collection.
- The Moxy Monitor is useful for researchers who know the capabilities of the system to perform laboratory tests.
- Coaches and sport scientists can use the Moxy for added information to field tests, such as shuttle runs or time trials.
- Strength coaches can evaluate metabolic relationships by placing the Moxy on superficial muscles that are propulsive.
- Sports medicine professionals can benchmark progress over a season or return-to-play period with at-risk muscle groups or zones of the body.
- It’s possible to get great value from just one sensor, but multiple units on the body add value to understanding how the local and global systems interact.
For the most part, the Moxy is robust enough for actual research but nimble enough to make daily use possible. I am in the middle; meaning, most of my efforts are to get insight into training methodology, and I will use the system to monitor an athlete daily if necessary. Since the system requires a favorable coaching ratio, it is not yet designed to serve as an enterprise product to monitor teams. It’s possible to monitor multiple muscles with multiple athletes at once, but logistically, the bottleneck comes from reacting to live data in a sensible fashion.For the most part, the Moxy is robust enough for actual research but nimble enough to use daily. Click To Tweet
Most of my recommendations are to help make very strong decisions or polarizing choices in training. As a simple summary, the purpose for Moxy in my world is to know whether a training approach is worth spending time and effort on. I prize changes locally now because the rise and fall of enzymes is difficult to see outside of invasive research. If you want to get basic trends, you need one Moxy Monitor; if you want to compare right and left muscle groups for locomotive activities, you need two.
Finally, if you want to see true changes, you will need an independent location or control sensor that monitors a low active muscle group such as the upper trapezius. It is a breath of fresh air to be able to contrast a muscle that isn’t working hard, if at all, with specific muscles that are being pushed to the limits. Regardless of the test, coaches will know whether an athlete is being held back by neuromuscular power, cardiovascular restrictions, pulmonary function, or the mitochondrial development internally. The approach is a bit of a process of elimination, but it works.
Who Should Invest in a Moxy Monitor?
Due to the relevance of the data to different professions, anyone in performance sport should invest in one sensor, and most teams will want a dozen to do small group assessments. It’s nearly repetitive to mention who would be interested in the Moxy data, but for the most part, everyone except a few purist sports psychologists will want it.
The primary candidates for the Moxy are the conditioning professionals that are either experts in endurance training or in repeated sprint ability with team sports. On average, those who use the Moxy Monitor the most are progressive ice hockey coaches, but expect soccer to match the interest coming from rugby. After strength and conditioning coaches will be the sport scientists, as they want hard physical data, not crude field tests. After the science crowd, medical staff who are progressive and able to do reconditioning training will round out the last group of professions.
A small percentage of applied nutrition science specialists make up perhaps the most intriguing group, because they connect dietary interventions with sport science. I am not saying this niche isn’t large enough to discuss; just the opposite—it is the future of sports performance because it evolves the sports nutritionist from the inappropriately labeled “food therapist” to part of the coaching staff. This paradigm shift from the unfortunate ivory tower stereotype to someone in the trenches is the change we need to see. Most solo coaches will likely want to either control their destiny by collecting the data or outsource the collection process to a private company or similar.
While hospitals and clinics do use NIRS, the Moxy Monitor is for exercise, not medicine. Click To Tweet
The Moxy Monitor is an investment, as the cost and time required to learn how to use the science and the system means it’s not for everyone. Generally, private facilities, college programs, and professional levels will reap benefits, but I am sure youth sports will demonstrate value down the road. It’s not a medical device, meaning that while hospitals and clinics do use NIRS, Moxy is for exercise, not medicine. Sports medicine professionals can use it for return-to-play programs, but it’s not appropriate for diagnosing a medical condition. As a training tool, Moxy is reliable and useful for making sharper choices in conditioning and power development.
The Final Recommendation with Monitoring Muscle Oxygenation
I don’t recommend coaches use the Moxy Monitor if they just want to look relevant or inflate their resume. Sports technology at high levels of sport is a must now, and coaches obviously feel the need to adopt the latest and greatest equipment to appear competent in sport science. In reality, they should spend most of their energy on polishing the basics by really understanding the core science.
What I love about the Moxy Monitor is that it forced me to be accountable with my conditioning approach by moving toward a more precise way of planning workouts. Getting to use the Moxy Monitor a few times a year with athletes is more than worth its price, and getting one for a team can make a difference in training and recovery.