The Moxy’s SmO2 Sensor Helps Make Base Training Even More Effective

This week on my VQ Velocity Virtual Studio, we are focusing on a week of Periodization and Taper. We are not performing hard intervals, but instead, we are focusing on easier rides. I wear my Moxy for all my rides, but most of the time, I focus on Desaturation and Resaturation. This blog post is about SmO2 and Base training. We can use the Garmin Connect Ecosystem to highlight the PHYSIOLOGICAL BENEFITS of low-intensity rides.

SmO2 and Base Oxygen Saturation Levels

SmO2 (Saturated Muscle Oxygen) readings show cyclists just how much Oxygen Supply is in the muscles. When a cyclist is riding for BASE, there should be plenty of oxygen available. As a ride progresses, the body warms up, and the blood vessels dilate. This offers the muscles more available oxygen. Think of SmO2 as ‘Volts’ in a car battery. When there’s a heavy draw on the engine (Demand), the volts may drop, like when the ignition is engaged. On electric vehicles, computers monitor watts (torque), volts, and Amps. I compare Amps with Total Hemoglobin, which I’ll discuss later in this post.

Since 2012, when I first started using SmO2 monitors from Moxy, I’ve discovered that SmO2 reveals great information about Base Training. When you first place a Moxy monitor on the left Lateralis, you usually get a reading of about 30-60% SmO2. I call this ‘Active Resting SmO2’. As you warm up, SmO2 will definitely drop a bit. If a cyclist or runner does NOT perform my trademarked Warmup Protocol, SmO2 dilation does NOT reach its’ full potential, and in my opinion, restricts some of the benefits of visualizing this feature. But IF the cyclist DOES perform my Warmup Protocol, then SmO2 can become a highly effective, visual method of visualizing just what Base provides.

Base Training Is an Energy-Positive Ride

Watch this 30-second advertisement for Del Monte Green Beans. Specifically, watch what happens when this young lady goes on a bike ride. This is EXACTLY what a ‘Base’ Ride should provide a cyclist or a runner. It should be ‘Energy Positive’ for mental wellness and spiritual fulfillment. It’s literally the way most of our bike rides should occur. The time you spend out there performing this may depend on goals, etc., but SmO2 can provide a window into exactly what is happening when a ride like this occurs.

SmO2 and Base Lead to Greater ‘Volts’ of Available Power, While Drawing Less ‘Amps’ (ThB) for the Same Amount of Physical Output

In this graph, you can see how my post-warmup Base ride begins with roughly 52% SmO2. While power output changes very little, vasodilation occurs, and available SmO2 rises at roughly the 45:00 mark, with a small dip in power output. The Smo2 continues to rise after that, until I perform a single 1-minute standing effort to change my saddle position.

***Standing Power is INCREDIBLY INEFFICIENT.

If you watch old videos of Alberto Contador, there are times before he had a serious crash, when he would climb seated, and honestly, he was a GC or stage threat. After his crash and long recovery, his body was never the same, and he climbed standing for even longer periods of time. It was very powerful, but very costly. 

However, after that single effort, SmO2 rose further, with little change in power.

Why Did SmO2 Start to Decline at the 1-hour mark?

Right around the 1:05 timeline, SmO2 began to decline. When we use Garmin Connect to zoom in, we can see that it began with a slight rise in power output. This was further exacerbated by another minute of standing and pedaling. SmO2 dropped further. Once I sat down, SmO2 Resaturated, but then continued its’ decline back to around 50%.

Why did this happen? Well, let’s look at the OTHER data point that we get when we ride with a Moxy; ThB.

What is ThB?

ThB stands for ‘Total Hemoglobin’, and it’s based on Millimols per Deciliter of volume. It’s the total count of red blood cells in your overall system. Hemoglobin is a protein that carries Oxygen to the Muscles. It’s another window into the ‘SUPPLY and DEMAND’ side of the SmO2 Equation. The more ThB we have, the more ‘AMPS’ we have available to help provide fresh oxygen to the muscles, to help keep SmO2 high.

Right around the 1:05 mark, when my SmO2 began to decline, Total Hemoglobin, which was declining from minute 33:00 to that point, began to rise. After the final standing moment, it rose further, and rose until I quit the ride at the 1:15 mark. So, SmO2 declines and ThB rises, for the same amount of power.

Now, this is CONJECTURE, because I AM NOT A SCIENTIST. But my own speculation is that I was getting short on blood sugar. I always ride these easier rides in a fasted state. It’s a way to train my body to burn more fat over time, as long as I don’t push too hard. But there are only between 800 and 1200 calories of carbohydrate in the circulatory system at any time, and in the 30 years that I’ve been cycling, my body tends to change at roughly 1200 calories, WITH CARB SUPPLEMENTATION. Without Carb supplementation, I think it’s very feasible to ‘see’ the body switching energy systems or becoming less efficient. At this point, I had burned roughly 800 calories, and had consumed nothing more than water (and probably not enough of that). Hence, ThB rose, SmO2 declined, while power and basic heart rate remained neutral.

Use Your Moxy SmO2 And Keep It HIGH!

My personal SmO2 Floors and Ceilings are as such, but your own zones may vary.

• My Max Recovery Saturation is at 80%. I rarely get there on an active bike ride, so 70% means my Muscles are being resupplied with fresh Oxygen and are ready for another effort.
• My Active Base Saturation is between 40 and 70%. When I ride at those SmO2 intensities (remember, harder is lower, easier is higher), my body is using energy to make energy in my  mind, and these are fruitful, fun, functional rides.
• An SmO2 below 20%, and usually below 17% puts me on ‘BORROWED TIME’, and is my Vo2Max range of intensity. It’s also unustainable for long periods.
• An SmO2 between 20 and 25% is a great Threshold Intensity for me, regardless of the old-school heart rate and wattage values that have traditionally yielded these zones.

If you really want to get a window into your body, SmO2 (and ThB) provide real-time value to help you optimize your ride. Once you know your numbers, you can always try to track gains in power or loss in weight over time. You can also watch ThB to see if you’re perhaps in need of some carbs, or may even be approaching a bonk.

I’m going to continue to share my observations. If you own a Moxy, let me know if you see similar phenomena. I’d love to learn more.

Thanks for reading, and ENJOY THE RIDE!