Using the Moxy Sensor At Elevation Reveals A LOT About Adaptation Requirements to Altitude

Moxy Stage 2 Ft Davis HammerFest

As most of you know, I am always searching for ways to use technology so that we can better understand cycling fitness and performance. I’ve been using the Moxy Muscle Oxygen Sensor since 2014, and have developed some strong ideas about how its’ use in our studio can help us understand the following:


·         Proper Warm-Up Procedures for maximal saturation and vasodilation.

·         Fatigue when performing intervals.

·         Glycogen Depletion and replenishment.

·         The effect of intensity on muscles before, during, and after intervals.

·         Dehydration.

·         Recovery and Optimizing the timing of caloric replenishment.

As the Moxy became more common, Garmin got on board, and allowed their smart head units to accept SmO2 and ThB from Moxy’s on to the screen via custom fields, and once on screen, this data is now being recorded in the latest .FIT files, so it allows me the chance to look at information both acutely and empirically. Having these two data points, along with Heart Rate, Wattage, Cadence, Speed, Slope,  and elevation, has really opened my mind towards just what is possible, and what isn’t.

Well, we can now add a new phenomenon to my amateur observations; what happens when a cyclist trains at low elevation, but competes at a significantly higher elevation.

On April 1st and 2nd of 2017, I traveled from my home in Dallas, TX (elevation ~430’ or 130m above Sea Level), to Ft. Davis, TX, to compete in a Stage Race known as the HammerFest. Last year, my wife and I traveled out two days early, and rode some, to try and adapt to the elevation (5050’ or 1540m) and dry air. I’ve raced and ridden out here enough to know that my performance definitely suffers, and the goal in the weeks prior to the event is to raise my Threshold as high as possible, while also trying to raise my Vo2max. It’s a tall order, but there have been years where I’ve competed well. That said, most of the time, it’s a real struggle, and I have to believe it has much to do with showing up just a day before the race, and making the first stage, my body’s introduction to strain at elevation.

Now, thanks to the Moxy, I think I have the proof.

In the weeks building up to the competition, my intervals routinely showed rising wattages, with SmO2 levels bottoming out in the 25% range, give or take. I’ve known athletes who were able to take their SmO2 values down to the teens and single digits, but they came from a power-lifting background, and tended to be on the heavier side; perfect for most Texas cycling, but not ideal for Ft. Davis.

On the morning of April 1st, however, when I performed my warmup, I was SHOCKED to see that my Moxy was reading in the  MID 50% range, as soon as the signal was picked up by my Garmin 1000. At first, I felt this was a result of the low temperature, but as I went through my warmup, I saw that SmO2 would routinely drop down to 10% during my warmup efforts, but would rebound over time to a more-expected 70% or more.
SmO2 Stage 1 Ft Davis Hammerfest

Now, the first thing to consider is that during my warmups at lower elevation, I never began an interval set until my SmO2 would rebound to AT LEAST 85%, and as high as 92%. Furthermore, it takes me about 30-35 minutes to get my ThB values up to about 12.40. When I’m at both of those numbers, or close to them, I know I’m vasodilated, that my core temperature has risen, and my legs, at least (I measure at the Left lateralis), are ready for any efforts I throw at them.

On this morning, however, SmO2 never went above 79%, ThB never surpassed 12.34, and again, as soon as I put any real effort in to my surges, or the climbs, SmO2 dropped to between 8 and 15%, and ThB never changed.

Something was seriously off.
SmO2 Stage 1 Ft Davis Hammerfest Image 2

I finished the first stage, a Point-to-Point effort that climbed Mt. Locke, with three major climbs that finished at 6790’ (2070m), and was REALLY disappointed in my results. My watts were down, my cadence was low, I felt heavy and it felt like my legs were dead. As soon as the effort ended and I began to recover, my legs began to REALLY HURT, like I had just undergone a SEVERE resistance training protocol, with multiple sets of squats at high loads.

Disappointed as I was, I waited for my wife, who was also a bit disappointed in her performance, and we rode down together, to eat, recover, and prepare for the next stage, to be held that afternoon. Ironically, the physiological results of that stage were completely different, with an warmed-up average SmO2 in the 85% range, and a range-under-stress in the 30-45% range, which is MUCH more typical of my values during hard efforts. Furthermore, my ThB basically maxed at a stable at ~12.49, and the effort itself showed little change, around 12.00 or thereabouts. It did drop to 11.80-ish toward the end of the stage, but overall, my muscles “Felt” better, and I felt like I could challenge in the race. Now, it didn’t end up that way, but results aside, it’s the physiology that we’re studying in this post.

I’ll attach the files to the blog post if possible, and if not, I’ll try to set them up for download on Google Drive or something like that, for people to study independently, since, remember, I’m not a Scientist. I’m a hack.

So, what’s the lesson to be drawn from this? Without the Moxy, I never would have known just HOW IMPORTANT adaptation to elevation is for a cyclist, or any athlete’s, performance. During my first stage, I basically raced myself in to a deep state of muscle strain, and ended up sore for days afterward. Ironically, had I gone out on the Friday before the race, and actually performed some intervals of similar strain, I would have basically gotten through that penalty phase of adaptation, and would have been better prepared for the efforts at elevation on Stage 1. Who knows – I might have actually had an even better physiology for the 2nd stage, and would have been completely prepared for the third stage that was going to be held the next day. Sadly, a final winter rainstorm blew through the Davis Mountains overnight, and my wife and I both decided to skip a rainy, sleet-covered, 26 degree race with snow above 6000’ (1830m), and winds above 20mph. We’re both too old and cautious to try racing in those liminal conditions, especially when we know there’s really no financial reward to speak of, just a possible great story to be told from the ER.

The Moxy Monitor remains one of my most crucial elements for training and competition. Without it, I’m left guessing as to how ready my body is for work. I will definitely call off a training session if I see numbers that are ‘off’, and I also work hard, as a coach and as an athlete, to provide consistent, safe, effective protocols for warmup, hydration, and recovery.

Listening to your body is one thing; actually seeing it perform via wattage, heart rate, SmO2 and ThB, provides a holistic approach that is incomparable. I cannot WAIT to go back to elevation and ride – only this time, I’ll make sure I have an extra day squeezed in to actually perform some ‘elevation adaptation’ intervals, that will leave me more prepared to take on the slopes and loads required to achieve my best.