All athletes increased their ability to utilise fat as a fuel source, including at higher exercise intensities.
Mean body weight was reduced by 4 kg ± SD 3.1 (p = 0.046; effect size (ES):0.62), and sum of 8 skinfolds by 25.9 mm ± SD 6.9; ES: 1.27; p = 0.001).
But how was their performance?
Mean time to exhaustion dropped by ~2 min (±SD 0.7; p = 0.004; ES: 0.53). Other performance outcomes showed mean reductions, with some increases or unchanged results in two individuals (VO2 Max: -1.69 ml.kg.min ± SD 3.4 (p = 0.63); peak power: -18 W ± SD 16.4 (p = 0.07), and VT2: -6 W ± SD 44.5 (p = 0.77).
Was this an adaptation problem?
Athletes reported experiencing reduced energy levels initially, followed by a return of high levels thereafter, especially during exercise, but an inability to easily undertake high intense bouts. Each athlete reported experiencing enhanced well-being, included improved recovery, improvements in skin conditions and reduced inflammation.
In the end the athletes likes the health benefits even with the performance losses.
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.
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.
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.
tl;dr – Don’t expect to do keto, be in a large deficit, and expect to see performance gains on glycolytic activites.
A good video on lifting and the keto diet. Covers other aspects of performance from the perspective of a real clinician and what he sees in his patient population who does keto. Very truthful even if not totally pro keto at moments (overall it is very supportive of keto so no need to be afraid of watching).
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 is the Maximum Aerobic Function training method developed by Phil Maffetone. The goal is to train at a particular rate in order to build up your cardio base. This level of training is done at a particular heart rate that creates maximum fat burning and minimum reliance on carbohydrate stores in the body (glycogen).
The ideal heart rate for this training is derived from your age.
Minimum heart rate = 170 – age
Maximum heart rate = 180 – age
There are also adjustments for training and other health considerations but for this example suppose you are 50 years old. You would train at a heart rate between 120 and 130.
At this range, if you are fat adapted (keto or low carb diet) then you are burning the most fat possible and the least carb stores possible. This is about equivalent to a fast walk when you start where you can keep up a conversation without running out of breath.
This pace quickens as your fitness increases. Soon you will be running and not walking. The trick is to not push it even if you feel like you can do more. That extra beyond your MAF heart rate doesn’t come from body fat anyway.
Some of the instructions for placement of the heart rate strap refer to muscles. Since I have none it’s hard to place the strap relative to that. And my nipples are not where they would be if I hadn’t lost 120 lbs. This video was very helpful on where to place the heart rate strap.