Another VO2max Test

I have a friend, let’s call him Moe. Moe is 30 years old. Moe is not a low carb dieter. Moe has been inconsistent in his training for the past two years. Moe has recently taken up running again. Moe’s MAF number is 180 – 30 -5 = 145. Use the Heart Rate Calculator to see the numbers.

Moe took the same Vo2max test that I did at WVU Human Performance Lab. Here’s Moe’s fat/carb oxidation curves.

If Moe does MAF Heart Rate training at 135-145 is heart rate would be approaching his cross-over of fat/carbs kcals per minute. However, Moe wants to burn the maximum number of calories so he runs near his max heart rate. When he runs at a high heart rate, Moe is burning carbs and not much fat. Moe could adopt a low carb diet and run slower with the positive effect of increased fat loss and no need to burn carbohydrates.

Me vs Moe

I am 28 years older than Moe. Here’s my curve with my MAF Heart Range noted.

My max fat oxidation rate is around 11 kcal/sec. Moe’s max fat oxidation rate is around 9 kcal/sec. Moe’s max carb oxidation rate is 16 kcal/min vs my 24 kcal/min.


MAF and Resistance Training

I’ve spent a little bit of time thinking about the compatibility of MAF Heart Rate Training and weightlifting – generically termed resistance training (RT). Since the activity is relatively short duration and the heart rate isn’t past the MAF Heart Rate it seems on the surface like it would be compatible to do both.

One thing to consider is that VO2max testing is done on a treadmill which increases the speed and angle every couple of minutes. Resistance training lasts for seconds. The Rate of Perceived Exertion (RPE) of the VO2max testing isn’t all that hard until it gets towards the end of the test. The RPE of weightlifting is substantial under significant loads so using RPE as a test this would indicate that there is an issue.

My measurement for whether an activity is aerobic or anaerobic is the Respiratory Exchange Ratio (RER). RER is correlated to heart rate in the VO2max test but rarely considered in RT. There is a study which looked at RER in RT (Scott. Quantifying the Immediate Recovery Energy Expenditure of Resistance Training. The Journal of Strength and Conditioning Research · April 2011) in terms of Excess Postexercise Oxygen Consumption (EPOC). To review:

The respiratory exchange ratio (RER) is calculated as steady-state CO2 produced divided by steady-state O2 consumed and is typically defined from values of 0.70 representing total fat oxidation to 1.00 representing total glucose oxidation.

Here’s the RER data from the study for RT. Note the RER values are all well over 1.0 which indicates anaerobic exercise range.

Another interesting comment helps explain the RER values above 1.0:

During and after exercise, RER values above 1.00 are generally thought to be the result of nonrespiratory CO2 production: The bicarbonate buffering system, for example, involves the removal of hydrogen ions with concomitant CO2 production and hyperventilation blows off ‘‘extra’’ CO2. Yet a true measure of the RER is best found only when the system is in a steady state of gas exchange.

To the subject at hand:

Rapid glycolysis (as part of anaerobic metabolism) ceases when muscle contraction stops so that recovery is considered to be aerobic in nature. If this is true, both fatty acid and lactate oxidation may play a significant role in fueling the immediate energy expenditure needs of recovery. Unfortunately, substrate oxidation immediately postexercise and particularly after anaerobic-type exercise has not been studied well enough to draw specific conclusions. Because of this, it must be assumed here that when muscle contraction immediately stops, glycolysis is limited to the point where fat and lactate are the predominantly oxidized fuels.


FASTER Study Interviews

Zach Bitter was a participant of the FASTER study (Jeff S. Volek, Daniel J. Freidenreich, Catherine Saenz, Laura J. Kunces, Brent C. Creighton, Jenna M. Bartley, Patrick M. Davitt, Colleen X. Munoz, Jeffrey M. Anderson, Carl M. Maresh, Elaine C. Lee, Mark D. Schuenke, Giselle Aerni, William J. Kraemer, Stephen D. Phinney. Metabolic characteristics of keto-adapted ultra-endurance runners. Metabolism, Volume 65, Issue 3, March 2016, Pages 100-110.) Our BLOG post about Zach in the study (Zach Bitter – Another FASTER participant). Jeff Volek was one of the scientists doing the FASTER study. Endurance Planet interviewed them together in a three part series.

Jeff and Zach speculated about how long this could go saying that perhaps 5 hours would have been a better test. Based on Ben’s fat oxidation rate I’m not sure that would have been a good idea. Ben’s fat was dropping in a linear form but his carbohydrate oxidation was speeding up fits to a 2nd order poly.

Here is another interview with Zach about FASTER (Primal Endurance Podcast).

Rowing MAF Baseline

I did a 5KM Rowing MAF baseline on my new Concept 2 Rower.

I was able to hold my heart rate quite well. Here’s the screen capture of the PM5 screen – sent from ErgData to Concept 2 logbook site and then to My Strava.

My MAF heart rate is 112-122 and I was able to stay around the 122 number pretty well except around 20:00. I don’t believe that the strap was on correctly at that point. I shifted the strap and it fixed the number. I  need to follow the instructions and wet the strap.

Concept 2 Logbook Data

There’s a phone app called ErgData which syncs up with the Concept 2 logbook. Here’s the heart rate data from the workout showing the over and drop outs. Other than the anomalies it was pretty easy to hold the heart rate.

Here’s heart rate, pace and stroke rate.

My stroke rate was decently consistent. I can see my pace fell off as time went on which is to be expected on any MAF test. I was a bit sweaty at the end. Here’s the split times:

This shows a slowdown in pace and power as time went on at the same heart rates.

The logbook lets me export to CSV all of the data. I can smooth out the bad section. Here’s what that looks like:

After I got warmed up, I stayed above 115 and below 125 bpm. I should probably aim for 117 until I get better at staying in a more narrow range.

Not a bad start and definitely my longest row ever.


MAF Bike Ride

A couple of days ago I did a MAF bike ride. The ride was 1 hr 40 minutes.The route was up the Great Allegheny Passage Bike Trail.

Here was my heart rate data.

I was able to keep very close to my MAF heart rate for the majority of the ride time. There was a big hill in the way home that made it hard to hold the MAF rate near the end.


MAF Walk with New Polar Heart Rate Monitor

I bought a rower and Polar H7 heart rate (HR) monitor. I took the H7 out on my MAF walk/run this morning. I collected data on my watch and on the heart rate monitor. Both had dropouts at points but they correlated well. I want to get to where my RPE is accurate enough that I don’t need to keep checking the watch but I do have a tendency to push it up past my MAF HR range.

Here’s the heart rate data from the H7 HR monitor. The H7 reported an average HR of 107 bpm. I think I did not have the strap high enough in the first part of the walk.

Here’s the heart rate data from the Samsung Gear Sport Watch monitor (Strava data). The watch reported an average HR of 111 bpm.

Here’s the same graph out of Samsung Health app on the phone.

The 113 bpm grid line would be the bottom of the 112-122 bpm MAF range so the HR between 20-40 minutes should be on or above that line.

Looks like my warmup was too quick and my cool down still could be better but overall it feels pretty good.


I walked to the Post Office and then up the hills. Both of the GPS data were good.


It was a lot cooler at 57 degrees this AM so my performance was better. I accidentally paused the watch a couple of times so the Strava length was more accurate and I assume the splits were more accurate as well. I am getting to where I have to run in stretches to keep up the MAF HR and the stretches keep getting longer as well.

Here’s the performance data from the watch:

Exercise Intensity and Fat Burning

There is a common misconception that more exercise intensity burns more fat. It is true that more exercise intensity burns more calories but at some intensity level exercise burns more carbohydrates than fat. At even higher intensities there is no fat burned at all. Back to my chart of %VO2max (on the horizontal axis) vs calories of fat (blue) or carbs (brown).

The maximum amount of fat burning is at about 52% of VO2max. At around 78% of VO2max equal calories of fat and carbs are burned. After that point fat drops off quickly and carbs take over. At around 98% of VO2max all the energy comes from carbs. At this point the energy from carbs is over 20 kcals per minute which is nearly 2x the max energy that came from fat.

This is the reason that I have a hard time performing at high intensities. I just don’t have the carb stores to sustain longer high intensity efforts. This is why I changed my training to work more at the lower intensities where I can exclusively use fat as fuel.

It should be possible to push the blue curve over to the right farther through training. Zach Bitter’s numbers (Zach Bitter – Another FASTER participant) show that he uses fat for 98% of his energy at 75% of his VO2max. At that point I am nearly 50-50. I don’t think that this is just dietary fat adaptation but exercise adaptation. Zach can mobilize more fat energy than I can and training explains the difference.


MAF Test – Triathlete Friend

My friend, SVW, did a MAF test the other day (2018-06-27). He is 35 year old triathlete who runs regularly. His MAF Heart Rate is 135-145. Here’s his Heart Rate chart.

He did a fine job of keeping his HR between 144 and 145. He did not do a 20 minute warm-up but ran to get his heart rate into the range. His mile splits were:

He did well at holding heart rate and his pace was pretty even throughout. That’s what I would expect out of a trained runner (he has been running for 5 years).

SVW is fat adapted and did keto for a year or so. He still eats keto mostly (some off and on). He does believe he needs carbs to compete in marathons.

Compared to Me?

SVW is almost twice as fast as me at my MAF heart rate. Some of this is age. Some of this is conditioning. I was walking and he was running. Some of this is motivation. Here’s my MAF test splits.

I don’t believe that SVW is interested in MAF training. He’s convinced that where he is at he needs to build his anaerobic base.



Took today for a recovery day after my 5K walk with additional 5K warmup yesterday. Feel pretty good. Not sore or tired at all today but I want to respect the protocol and the 93 degree heat outside today to take a rest day.

Walked a total of 10K yesterday. Pretty sure that was the most walking I have ever done in my life. I credit Crossfit for getting me into the physical shape I am in now.

I am hopeful that the Maffetone method of Heart Rate Training will take me to the next level.

My watch indicates I trained for 5 hrs ,33 minutes in the last week.