Using Moxy to Determine Whether You're Fresh or Fatigued

Last Tuesday, one of my clients came to the studio for a class, and opened our conversation with “Man, I had a killer workout on Monday. I hope I’m ready for this.” We began to talk, and it was obvious that he was fatigued, both mentally and physically from the previous day’s effort.

Now, this cyclist is a top-tier mountain biker, who has properly allowed himself some “Down” time, to enjoy other pursuits. When he was on-form earlier in the year, he was literally unstoppable. He only got FASTER as the fall season progressed, and it was exciting to follow. But let’s face it - getting a power meter on a mountain bike is a chore, and honestly, I don’t like all of the options that are out there right now. It’s expensive, and when people have to choose between an expensive power meter, and 4 months of coaching or more, well, the bikes are expensive enough already. Furthermore, given the stochastic, punchy nature of Texas mountain biking, I often wonder if a 1hz reading from an MTB power meter is adequate to capture the nuances and accelerations that are necessary to properly analyze a ride.

But sometimes - Physics just doesn’t correlate with Physiology. While the computer or the prediction algorithm says you “Can” do something, it doesn’t account for all the things that may interfere, like sleep rhythms, recovery from a previous workout, hydration status, all of it. That’s where the Moxy Monitor comes in.

I honestly should be using this device more, but knowing how to use it does require a bit more attention to and knowledge of “what’s going on”. But with this conversation up, I decided to take a look at Randy’s SmO2 values, and try to help him do what was best with the time he was spending at the studio.

SmO2 image 1
Now, we have to review a bit, but here’s the summary:



SmO2 values will tend to hit ‘Floors’ which align with Lactate Deflection Points 1 and 2, when properly placed on a client’s Left Lateralis. MOST of the time, we’ll see cyclists hit a “Max Active Saturation Point”, of about 85-90%, and MOST of the time, LT1 will correspond with about 40-45% SmO2, and LT2 will correspond with about 25-30% SmO2. If you get down in to the teens, or single digits, theoretically, you’re nearing necropsy.


But it was immediately obvious that something was ‘off’. Nothing about Randy’s values were normal. I checked the position of the monitor, but it was good. There was no light pollution, either. His SmO2 during intervals that were supposed to be in the Vo2 range of intensity, were wayyy too low; like near 10%. When his recoveries between intervals occurred, he hit the regular ‘max’ 80% saturation around the first two efforts, but for the entire second half of the workout, his ‘recovery’ SmO2 never cracked 65%, and his interval minimums dropped down TOO low at first, and then, again, never really recovered. Here’s a better look at the chart.

SmO2 Image 2

Here it is with power added in…

SmO2 image 3

The translation, for me as a coach? THIS GUY WAS KNACKERED! THIS GUY WAS EXHAUSTED. We were lowering his intensity well below his Critical Power early and often, he wasn’t keeping up with load, and his SmO2 minimums were STILL down in the 20% range. The recoveries never rose up much past 55%. His range was diminished, his power down significantly. He had no business attempting a hard interval set like that.

Now, let’s fast-forward to this morning. It’s been two days; he had a massage and slept a good chunk of the day after the massage (some massages are actually therapeutic workouts, and the relaxation is done AFTER the therapy). He got nine hours of sleep, was hydrated, rested, recovered, and caloried up.

Here’s his chart from today…

SmO2 Image 4

It’s a little bit harder to see, but the results were MUCH, MUCH better. Maximum SmO2 was up above 90%. Minimum SmO2 actually never went below about 40%. WE RAISED HIS CP to try and get one specific area of the intervals to sort of ‘sit’ around 50%, and it never really dropped below about 58%. It was a complete reversal of fortune. He worked hard, left with great confidence, and honestly, we probably could have gone a bit harder, though I didn’t want to try that too much, and instead focus on the success of the day, and grow it from that point.

SmO2 via the Moxy Monitor allows you to see a workout from the INSIDE-OUT, and allows you to train via your Physiology, and not just your Physics. You’re not ‘on-form’ every day. Things happen. Diets fail. Work creates stress. Maybe the music isn’t just right. Maybe it’s the holidays or EOY junk. But it helps to have a place to go where you can get a great workout that’s JUST RIGHT for YOU, and YOU only. Matching the watts to the load is just part of the story. Moxy helps you accomplish that at Cycling Center Dallas. Come visit and we’ll show you how.









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