Exercising With Fitness Wearables: Which Metric Is Best?
Not long ago, athletes had limited ways to objectively measure their exercise intensity. For example, until recently, chest strap-based heart rate monitors were the standard tool used by athletes for measuring intensity and guiding training.
However, in recent years wrist-worn heart rate monitors, muscle oximeters, VO2 estimates, and even foot-worn power meters have become more common. Which raises the question, what’s the best metric for tracking exercise intensity? Read on to find out!
What Is VO₂? And Can It Be Accurately Measured With Wearables?
VO₂ or VO₂max has become a common way that people are evaluating their fitness level and heart health as they exercise. Some of this is due to the growth in VO₂ features on popular wearable devices. But what is VO₂, is it a true measure of your health and fitness, and how is it different from your muscle oxygenation (SmO2) level?
VO₂ is the volume (V) or oxygen (O₂) your body uses when you exercise. VO₂max, on the other hand, is the maximum amount of oxygen your body can consume, and it represents the maximal integrated capacity of the pulmonary, cardiovascular, and muscular system to uptake, transport, and utilize oxygen respectively. The higher your VO₂max, the more oxygen your body can consume and, in theory, the more fit you are. Over time, you should be able to improve your VO₂ with consistent and varied exercise.
However, measuring VO₂ is not a simple task. Accurately measuring VO₂ requires a lab-grade metabolic analyzer, requiring users to wear a cumbersome mask over their face, and wearable devices that display VO2 measurements are simply providing estimates based on the user's heart rate which have questionable accuracy.
Muscle Oxygenation, It’s all About the Muscles
The NNOXX One, on the other hand, directly measures muscle oxygen saturation (SmO₂), as well as oxygen consumption (mVO₂) in exercising muscles. SmO₂ is the percentage of blood in the skeletal muscle that is carrying oxygen, whereas mVO₂ is a measurement of local muscle oxygen consumption.
In simpler terms, SmO₂ measures a muscle's oxygen supply, while mVO₂ measures the amount of oxygen muscles use for energy production. Thus, SmO₂ and mVO₂ are more direct measures of oxygen supply and demand in active muscles and can provide valuable insight into how well those muscles function.
Additionally, SmO₂ and mVO₂ measurements give trainers and athletes an indication of when they need to rest or reduce exercise intensity to prevent fatigue and maintain optimal performance. VO₂, on the other hand, measures total body oxygen use and does not directly quantify muscle performance and fatigue.
What About Heart Rate? Where Does That Fit In?
Heart rate refers to the number of times your heart beats per minute, and it is one of the most used biomarkers for monitoring exercise intensity. During physical activity, your heart works harder to supply oxygen and nutrients to your body's muscles. As your exercise intensity increases, so does your heart rate.
The theory is that by monitoring your heart rate during exercise, you can adjust your workout intensity to match your fitness goals. For example, it is often said that if you want to improve your cardiovascular fitness, you should aim to exercise in a target heart rate zone that is between 50-70% of your maximum heart rate. However, heart rate may not be the most accurate or reliable indicator of physical exertion.
A recent study found that while heart rate was unaffected by continuous changes in terrain and intensity during exercise, SmO₂ reflected these changes and was strongly correlated with changes in oxygen consumption.
These findings suggest that SmO₂ may offer a more accurate alternative to heart rate for monitoring exercise intensity, particularly during running in hilly terrain. Additionally, compared to heart rate, SmO₂ provides a more direct and precise measure of exercise intensity and the body's ability to maintain performance. For example, two people with the same heart rate may be experiencing different levels of muscle oxygenation, meaning that one person is working harder than the other. This can make a significant difference in the metabolic benefits they get from their workouts and could impact their fitness goals.
Practical Takeaways
In conclusion, while VO₂, and heart rate are still worth measuring as whole-body systemic indicators of exercise intensity, muscle oxygenation (SmO₂) and oxygen consumption (mVO₂) offer more reliable indicators of how exercise is affecting the working muscles. This can be particularly helpful for monitoring and optimizing resistance training, where muscle activation and local muscle oxygen consumption are critical factors in achieving the desired results
By incorporating SmO₂ and mVO₂ measurements into exercise monitoring, athletes and fitness enthusiasts may be able to optimize their workouts and achieve their fitness goals more effectively.
Start Monitoring Your Muscle Oxygenation (SmO₂) And Oxygen Consumption (mVO₂) Levels Today
NNOXX One is the first and only wearable that can measure your muscle oxygenation, oxygen consumption, and nitric oxide levels in real-time as you exercise, helping you to optimize your exercise intensity, duration, and recovery time.
NNOXX One will help you make the most of your time spent exercising, whether your'e performing high intensity interval training, longer workouts to improve your cardiovascular health, or lifting weights to increase your lean body mass and muscle size.
NNOXX coaches you to measurable improvements in your fitness and performance. For a limited time you can save up to $200.00 off your NNOXX yearly membership.
