If you're new to muscle oxygen monitoring with NIRS technology like the Moxy Monitor, you might be wondering about the two main metrics displayed: SmO2 and THb. Let's break down what these measurements mean and how they can help optimize your training.
What is SmO2 (Muscle Oxygen Saturation)?
SmO2, also known as muscle oxygen saturation, or muscle oxygenation, represents the percentage of hemoglobin and myoglobin that are carrying oxygen in your muscle tissue. Think of it as a gas gauge for your muscles - it shows the balance between oxygen supply and oxygen demand in real-time.
SmO2 is expressed as a percentage from 0-100% and while the number itself doesn’t mean much from a training perspective, HOW it’s changing does!
- Increase values: Your heart is supplying more oxygen than the muscles need, meaning you have plenty of oxygen available
- Stable values: Your heart is supplying the same amount of oxygen that the muscle is using.
- Decreasing values: Your muscles are working hard and consuming oxygen faster than it's being delivered
SmO2 responds immediately to changes in exercise intensity, making it an excellent tool for understanding training zones and pacing strategies.
What is THb (Total Hemoglobin)?
THb measures the total amount of hemoglobin and myoglobin present in the muscle tissue under the sensor. This metric reflects blood volume changes in the muscle and is measured in arbitrary units.
THb tells you about:
- Blood flow changes to the muscle
- Indications of metabolite build-up within the tissue
- Potential vascular adaptations over time
Unlike SmO2, THb doesn't have a standardized 0-100% scale. Instead, it shows relative changes from your baseline values.
Key Differences at a Glance
|
SmO2 |
THb |
|
Oxygen saturation percentage |
Blood volume indicator |
|
0-100% scale |
Arbitrary units |
|
Shows oxygen supply vs demand |
Shows blood volume changes |
|
Primary metric for training zones |
Secondary metric for blood volume analysis |
|
Changes rapidly with intensity |
How to Use Both Metrics
For most athletes, SmO2 is your primary focus for training optimization. Use it to:
- Identify training zones and breakpoints
- Monitor fatigue during workouts
- Optimize warm-up protocols
- Guide real-time training intensity
- Autoregulation of interval training
THb provides supporting information about:
Getting Started
When you first start using a Moxy Monitor, focus on understanding your SmO2 patterns during different types of workouts. As you become more experienced with muscle oxygen monitoring, THb can provide additional insights into your body's physiological responses.
Remember, both metrics work together to give you a complete picture of what's happening in your muscles during exercise - helping you train smarter, not just harder.
Want to learn more about using NIRS technology for training? Download the Training and Racing with Moxy eBook below to learn more about effective training and racing with Moxy Monitor.
