Vo2 at Threshold – Affirming Outdoor Power at Threshold

In my last blog post, I mentioned that for my best 10-minute effort while climbing a trail on a mountain bike, my Vo2 at Threshold read as roughly 55ml/kg/min. I also believed that my Vo2Max was roughly 62ml/kg/min. I was curious to see if these values were valid, so I went back indoors. At my home studio, I performed five weekly 20-minute efforts, specifically to determine whether those two values, Vo2 at Threshold, and Vo2Max, were accurate.

 

Percentage of Vo2Max When Cycling at Threshold Intensity

There’s a lot of new information coming out about the determination of Training Zones. Essentially, each method of measurement tends to come up with its’ own value, and training zones are then based on those values. Let’s face it – Vo2 at Threshold is expensive to acquire, since it requires a Vo2Master, a Polar H10 chest strap, a Moxy, a Power Meter, and probably a Lactate Tester, which is a product I have owned in the past, but do not own at this time. Instead, I use the Moxy and other readings from the Vo2Master and my Polar H10 chest strap, to determine the most accurate Threshold value for myself.

By looking at ALL of the values, however, I could then apply each of them when training. If the goal is to raise Vo2Max to its’ highest time-limited potential, and to raise % of Vo2Max at Threshold, then having those other metric markers can help me take a more holistic approach to every ride.

The Workout

For these five tests (and probably counting), I used my standard indoor training software, PerfPro Studio. My warmup consisted of a 27-minute protocol that I’ve honed using Moxy muscle oxygen sensors. I did roughly four Vo2master O2 calibrations for each workout, but I only recorded the 20-minute effort on the Vo2Master app. The Vo2Master is best used in a consistent atmosphere, so I used a local 8000 btu air conditioner in my small room, to help keep humidity and temperature under control.

Here are the results:

Date	20Min Vo2 Average	20Min Power Average	20Min HR Average	20Min RR Average	20Min DFAA1 Average	20Min SmO2 Average	20Min EqO2 Average	Best 30-sec Vo2max	Vo2 as a % of Max
6-Oct	53.5	271	163	35	0.5	6.8	22.2	62.6	85%
13-Oct	55.1	287	172	39	0.4	15	24.5	60.6	91%
20-Oct	57.5	281	170	42	0.4	20	24.5	65.2	88%
27-Oct	56.9	273	172	43	0.43	10.2	25.3	63.2	90%
3-Nov	56.9	273	172	43	0.4	10.2	25.3	63.2	90%
AVERAGE	55.98	277	169.8	40.4	0.426	12.44	24.36	62.4	89%
HIGH	57.5	287	172	43	0.5	20	25.3	63.2	91%
LOW	53.5	271	163	35	0.4	6.8	22.2	60.6	85%
RANGE	4	16	9	8	0.1	13.2	3.1	2.6	5%

What the Chart Says

There’s more information on this chart than just Vo2 values, but here’s the summary…

• My 20-minute average Vo2 over 5 efforts was 56ml/kg/min. This is comparable to the 55ml/kg/min that was observed in the mountain bike climb from the previous, outdoor, post.
• The highest 30-second Vo2 value over the same 5 efforts, which I’ll call Vo2Max, was 63ml/kg/min. Again – I’ve seen this ‘Vo2Max’ value enough to believe it is accurate. Incidentally, my Garmin 1040 and Garmin Connect continue to show my Vo2Max, per calculation only, at 59-60ml/kg/min, which I believe tracks pretty well, even though it is not using metabolic values, and instead uses calculations.
• When you take the 20-minute Vo2 at Threshold, and divide it by the 30-second Vo2Max, well, my Vo2 at Threshold occurs at about 89% of my Vo2Max.

Notice that I have not mentioned power, or watts. I’ll explain why…

Vo2 at Threshold is a PHYSIOLOGICAL PHENOMENA

For 27 of my 31 years as a Professional Cycling Coach, pursuing watts at Threshold, watts at Vo2Max, and watts per kilogram per minute, has been a stated priority. However, Physics is immutable, while physiology is incredibly mutable.

For the same amount of physiological effort on the outdoor effort in the previous post, I averaged maybe 235 watts over 10 minutes, and 207 watts over 20 minutes. For these five indoor tests, I averaged about 277 watts over 20 minutes. The delta is too great to ignore.

On that same ride, I averaged 165 beats per minute for the climb, while on these five indoor rides, the average heart rate was 170 beats. Temperature, convection, and evaporation are important considerations for heart rate intensities.

For my climb outdoors, which was not 20 minutes, the average DFAA-1 on AlphaHRV was about a 0.4. For the 5 indoor efforts, it was 0.43. I am becoming more and more convinced that there is something ‘there’ there when it comes to DFAA-1 and Threshold.

Finally, the SMO2 value for my climb was about 25%, while the SMO2 average for the 5 indoor 20-minute efforts was 12.4%. I’m convinced that this is because of micro-recoveries on a mountain bike trail, vs. the consistent resistance of a 2% slope indoors.

I think I want to optimize my physiological markers going forward, and those of my clients, and let the watts take care of themselves from now on. Chasing watts as a primary metric, especially on a mountain bike, can leave a rider disillusioned and frustrated.

Conclusion

Vo2 at Threshold is a great way to assess your current fitness, but it requires expensive apparatus. I still don’t own all of the kit I could possibly wear that would help with this assessment. Knowing that my Vo2 at Threshold, is roughly 89% of my Vo2Max, does reassure me that my fitness, at least in August of 2024, and again in October of 2024, is pretty close to my genetic potential.

The next step, one I won’t attempt until the Spring of 2025, will be to try and grow that Vo2Max up to a 65, 66, or even 68ml/kg/min. This will be INCREDIBLY difficult to achieve as a 55-year old male, but I’d like to try. The next step would be to see if I can HOLD my Vo2 at Threshold near 90% as that Vo2Max rises. This is going to require losing another 2 kilograms of mass, maybe 3. That MAY affect my power output and fatigue levels, so I have to temper action with wisdom on this as we go into the 2025 PreSeason.

Winter is approaching quickly, and the cooler temps mean that I won’t be able to use the Vo2Master outdoors nearly as much. When the snow finally leaves the trails unrideable, I’ll be hyper focused on my indoor efforts in my VQ Velocity until Spring. But until then, I’ll be riding outside on the mountain bike on my beloved Peavine, trying to keep my singletrack skills and dreams alive until April 2025, when I can get back out there again.

I’ll post some follow up blogs about the other metrics featured in the chart above, but I need to consult with some PhD’s that are wiser than I am on these parameters. I also have to thank my client, Ken O’Brien, a retired Bell Labs professional, on his coding assistance for a new project that I’ll reveal next.

Thanks for reading, and ENJOY THE RIDE!