Podcast Review: Zone 2, Max Aerobic Function, and HRV
#144 - Phil Maffetone: Optimizing Health and Performance Through Maximal Aerobic Function [The Drive: Peter Attia]
Reasons To Listen:
1hr 22min
Max Aerobic Function (MAF), MAF HR, MAF Pace
Calculating your MAF HR with Phil’s 180 formula
MAF training considerations
My Take Aways:
Defining aerobic vs anaerobic.
Phil dislikes the commonly used definitions for aerobic and anaerobic energy systems. Rather than using ‘in the presence or absence of O2’ as a determining factor, he suggests to think of the fuel being burned as a more simple marker.
Aerobic = fat utilization
Anaerobic = carb/glucose utilization
Why VO2max isn’t a great predictor for performance?
VO2max is loosely defined as your bodies ability to utilize oxygen or the difference between the O2 you breath in and the O2 you breath out. The difference between those values is the amount utilized.
VO2max is commonly thought of as a cardiovascular test (and it certainly is) but it is more about the ability of your muscles (mitochondria) to consume and utilize O2. You can get as much oxygen to your muscles as you want but what matters is how much can they actually use.
Although VO2max is a commonly cited performance metric (big time bragging rights) for athletes, it doesn’t correlate well to marathon time/race performance amongst similarly grouped athletes. I was shocked to hear that.
In a group of heterogenous athletes (untrained -> trained -> pro) VO2max does a good job of predicting performance however, in a group of homogenous athletes (pro vs pro) it does not. What may be of more value is sub max VO2 values.
Phil’s MAF Test and the corresponding MAF HR and Pace.
MAF is the distance or pace you can run while maintaining your MAF HR.
An improvement in MAF would be maintaining your MAF HR while running faster or further.
Although Phil doesn’t use ‘Zone 2’ as a descriptor, this is basically a way to use biofeedback (HR) to stay and train in Zone 2, without having a lot of fancy equipment.
I am currently playing around with this idea. It is simple to standardize on an individual level and track progress. I calculated my MAF HR according to Phil’s formula and picked a pace on the treadmill and ran for 40 minutes seeing what my HR would do. As it slowly crept above my pre-determined HR I would dial back the speed to get a corresponding drop in HR.
As HR is constantly moving up and down I decided to make my decision to change speed on a 5 min clock, where if my HR was constantly above my MAF HR for 5 min then I would dial back the speed.
Over the course of 2 weeks I have already seen an improvement in my HR over the set time and distance I’ve been running.
Calculating MAF HR
180 - Age
Modifiers
-10 more if you’re taking ANY medications (not incl. vitamins or supplements).
-10 if recovering from illness, rehabbing an injury, or are experiencing overtraining/overreaching.
-5 if you have minor health issues (get sick a few times a year), are out of training, or are “over fat”.
+5 if you have no health issues.
Phil suggests that it may take 3-6 months to reach a plateau in MAF. In other words you will continue to see gains for a while in your pace at the same HR.
Do not change HR until you have reached a plateau unless a modifier changes.
No ‘research’ was stated for these calculations and seem to be derived from Phil’s experience working with runners and an analysis of his data. So take that as you will.
Your experience of running at your MAF HR should match your perception of a zone 2 training effort, RPE of 3-4, a conversation pace, or an all day pace.
Relationship between diet (carb intake) and energy utilization.
Phil and Peter discuss their experiences with athletes on a low/no carb (keto) diet and the impacts on fuel utilization in the muscle.
They suggest that the assumption you can only burn 1g/min of fat is not necessarily true and that carb restricted athletes can burn upwards of 2g/min (anecdotally).
I’m onboard with the idea that nutrition can play a huge role in the body’s ability to utilize energy and should be structured based on the athletic goal.
Getting faster at a sub-max pace translates to being faster at a max (race) pace.
This makes sense to me. If you’re able to keep your fat oxidation going for longer before fully flipping to glucose as a fuel, you will fatigue less quickly.
Some quotes
“Over-fat” not “over-weight”
Show Notes are here.
#85 - Inigo San Millan: Mitochondria, Exercise, and Metabolic Health [The Drive: Peter Attia]
Reasons To Listen:
2hr 53min [During Phil’s podcast, Peter mentioned a podcast on zone 2, so I found it and listened… 3x, so much to digest and comprehend, but wildly informative at a scientific and anecdotal level]
Muscle fibres and their preference for fuel types
Mitochondrial function and performance in aerobic training
Elite endurance athletes have the ‘healthiest’ mitochondria in the world
Training broken down into 6 zones with a heavy focus on zone 2
Lactate as a fuel, not a waste product
It is a great indirect measure of mitochondrial function
My Take Aways:
When exercising in any capacity it comes down to the muscle contraction. Based on the type of exercise being performed or adaptions you are looking for you will get different recruitment of muscle fibres that are best specialized for the job. You can train these qualities to an extent. Genetics is a factor.
Type 1 vs Type 2 skeletal muscle fibres
Type 1 (slow twitch) - really means slow fatigue; aerobic; endurance
Type 2 (fast twitch) - really means fast fatigue; anaerobic; sprints, intervals, max efforts
Exercise intensity determines your bodies need for ATP and the subsequent source of energy.
2 main sources
Carbs/fat and glucose
Type 1 best utilize fat as a fuel due to their high concentration of mitochondria
low intensity exercise = less forceful contraction, don’t need ATP as quick
Type 2 fibres best utilize glucose (less mitochondria)
high intensity exercise = more forceful and frequent contraction, need ATP much quicker
ATP is our energy currency
Training in an aerobic state means that our demand for ATP can be met by the mitochondrial oxidation of mainly fat (This oxidation of fat in the mitochondria is where oxygen is needed in the system and where the ‘aerobic; in the presence of oxygen’, definition was born).
Anaerobic training means that our demands for ATP have exceeded the capacity of the mitochondria and we must switch to a faster fuel source (glycolysis) that doesn’t require oxygen in the process.
Inigo has a great analogy for his zones of exercise intensity which I will explore further in a different post.
6 zones of intensity
Based on muscle fibre recruitment and energy source
Zone 1 - day to day state, recovery state; minimal stimulation of muscle fibres
Zone 2 - utilizing type 1 muscle fibres to their fullest
“Fat max” - mitochondrial oxidation of fat is producing most amount of ATP possible
Most efficient state
Lactate is being produced but re-utilized as fuel for mitochondria in slow twitch fibres - so no/minimal increase in blood is seen
Zone 3 - transition zone as you switch from fat oxidation to glycolysis for energy production
Increase in type 2 fibre recruitment
May start to see higher lactate build up in the blood
Zone 4 - using glucose as your main fuel and you approach your lactate threshold
lactate is definitely starting to build in blood
Lactate is an important secondary fuel source
Lactate gets a bad rap for being associated with pain and fatigue after intense workouts.
It probably has more to do with an increase in hydrogen ions associated with lactate that are the villains in this scenario. Hydrogen ions:
Decrease the contractive capacity of the muscle (speed)
Decrease the force of muscle contraction
Lactate has different fates depending on the intensity of exercise
It is a bi-product of glycolysis but this can, and is, taking place during aerobic exercise (NOT just anaerobic, the processes are never fully separated).
It can be transported into the mitochondria of type 1 fibres to be burned as a fuel to produce ATP.
It is less efficient than fat as a fuel (less ATP produced)
During low intensity exercise, this is likely lactates fate.
As exercise intensity increases, mitochondrial function is slowed and there is a higher rate of glycolysis to provide ATP quicker. The muscles ability to clear and utilize lactate becomes overwhelmed and then lactate starts to get shipped into the blood
It can be sent back to the liver for storage as glucose
The muscular environment begins to change and pain/fatigue set in, as mentioned above
World class endurance athletes are better able to utilize lactate as a fuel source and it takes much higher exercise intensities before it starts to build up in the blood.
Inigo’s hypothesis for improving mitochondrial function is to train at max mitochondrial output ie. height of zone 2. (I believe this is a more technical answer but synonymous with Phil’s MAF concept).
Based on Inigo’s research, zone 2 is the intensity where you see the biggest improvement in fat burning, lactate clearance and increased performance.
Zone 2 is relative to the individual. An elite endurance athletes zone 2 will be at a much higher speed or power output than an untrained individual.
Elite endurance athletes have 3-4x the concentration of mitochondria, larger mitochondria and better mitochondrial function.
It is important to use physiological parameters to guide training not just mechanical parameters.
The ability for humans to perform relies on conversion of chemical energy to mechanical energy.
Mechanical energy can be tracked in terms of power, force etc.
HR is a physiological parameter and thus responds to physiological/metabolic stress (as are lactate and HRV).
Lactate is much more inconvenient to try and track on a regular basis outside of a sport science lab.
Sleep, nutrition, stress, and recovery will all impact a physiological parameter. So training at a fixed power output (cyclists) without considering HR, for example, could lead to training at a much higher relative intensity than you were planning on and lead to over training.
Inigo and Peter spend time anecdotally talking about how diet impacts these physiological markers.
They have a similar take as Phil Maffetone, however, they don’t agree on the speed of adaptation.
Anecdotally, a switch to a carb restricted diet is likely to decrease performance in the short term and perhaps even up to a year. There are likely benefits to fat utilization after adaptation takes place. How long that adaptation takes is the question.
Inigo relates that elite cyclists that have tried this lose significant performance compared to their peers and thus suggests it is not recommended for elite athletes actively competing. The performance from their glycolytic systems is too valuable to mess with in their primes.
Had they grown up with this adaptation they may be able to acquire unseen performance metrics related to fat metabolism compared to their peers.
How much zone 2 training is needed?
2 days a week seems to maintain your level
3-5 days a week seems to move the needle and you will see gains in aerobic function
This is not going to happen in season as you will have many other different exercise intensities to train
Show Notes are here
#44: HRV - World Class Readiness or Waste of Time [Science for Sport Podcast]
Key Features:
26 min
Defining HRV
HRV as a metric to capture an athletes readiness to train that day
DC Potential as another measure of athlete readiness
My Takeaways:
Heart Rate Variance (HRV) is a measure of the difference (in time) between heartbeats (specifically the R-R interval). Measuring these electrical impulses gives you a sense of the function of the autonomic nervous system.
Sympathetic and parasympathetic activity
HRV is an objective clue to the stress on ones body beyond training inputs (rest, recovery, fatigue, mental or psychological stress, nutrition, mood, anxiety) and a way to better understand an athlete’s response to their previous training and how their body is tolerating the day.
A “look under the hood”
HRV is best utilized as an objective measure to compare with the athletes subjective reports for the day.
A way to compare their “psycho-physiological function”
One of Whoop’s (a fitness tracker you may not be familiar with) main qualities is the ability to track HRV and they have built it into their recovery score.
Cody describes that you shouldn’t be glued to a periodization protocol as we can’t predict that the training input or stimulus will directly correlate with the athlete’s output that day.
In other words, they may be more worn down than expected or vice versa, be feeling great when the periodization may suggest rest.
DC Potential or DC current is a similar metric but looks through the lens of the central nervous system (CN), where HRV is ANS.
I had never heard of this until I listened to this podcast, so don’t have anything to add other than what Cody says about it.
Cody is a proponent of the Omega Wave System
This is a product you use before you start the day’s training to get a sense of the “brain-body interaction”. Basically, your bodies arousal level.
If your DC potential is low, that would suggest a high intensity activity would not be handled well that day and you could adjust training accordingly.
Show Notes here
#108: World Renowned HRV Researcher Daniel Plews Discusses Everything You Need To Know About Performance and Training.[Whoop Podcast: Will Ahmed]
Reasons To Listen:
46 min
Block periodization vs HRV-based training
HRV as a metric to capture an athletes readiness to train that day
Importance of averaging HRV scores; not a single snap shot
Using HRV as a tool to select training for the day
My Take Aways:
Block Periodization vs HRV as a training model
Block periodization is a classic training model where you train in ‘blocks’ of time to work on a specific adaptation or quality. This changes based on where you are in your competition season and is quite structured in theory.
HRV modelling is based on selecting an activity for the day based on the athletes HRV.
They were compared in a study which found similar results in VO2, but the HRV-group had a significant increase in max running velocity. HRV achieved that goal with relatively less high-intensity training.
HRV is a better indicator of how the athlete is feeling that day.
If HRV is low - then it calls for a lower intensity activity (than perhaps was planned). This will allow for a better adaptation from the training response rather than pushing too hard when the body is not ready to handle that stressor.
This could be due to a number of factors surrounding the athletes recovery from last days effort.
This contrasts the rigid modelling of periodization which has a pre-determined plan for you regardless of how you feel or taking into account physiological markers.
Periodization misses the contextual factors of the athlete and assumes a direct relationship b/w training and fatigue.
HRV captures the entire day and the additional stressors that may be present when the athlete is not at training.
Daniel also uses it as a way to open a conversation with the athlete. If their HRV is not where you thought it should be, sitting down with the athlete to discuss why that recovery didn’t happen is important.
They emphasize the importance of “showing up with capacity” to training; what you do away from training impacts your next day capacity.
Daniel’s 3 pillars of recovery are sleep, nutrition, and training strategy
“It’s impossible to go too hard, only too hard too frequently”
Daniel suggests that a single day snap shot of HRV isn’t always perfect and not the best way to utilize the data , he prefers the idea of rolling averages and following it as a trend.
HRV should “provide more certainty in making a decision rather than making the decision for you.”
An improvement in HRV is generally defined as it increasing over time. However, athlete’s don’t always seem to have a great performance when they ride that high right into competition.
Having some time to recover pre-competition returned better performances (HRV came back down a bit)
They described this phenomenon as ‘functional over-reaching’
Alternatively, if you’re training hard and HRV is decreasing that is also a problem.
Daniel has pre-determined groupings of activities categorized as low-HRV, mid-HRV, and high HRV. Based on the athletes HRV and other factors for the day, an activity is chosen from one of the categories.
The activity or adaptation you are choosing on a given day is based on how the athlete has recovered from the previous session.
Daniel discusses his nutritional strategy of “healthy fat, low carb”
An individuals nutritional strategy should be based on the event they are competing in and their expected result.
“Different horses on the same courses”
An 8hr triathlete will need much different fuel demands and adaptations in place compared to an 10hr triathlete.
This would change nutrition during training as well as competition nutrition.
Show Notes here
