Heart Rate training zone systems take for granted that a fairly high level of sustained aerobic effort is comfortable or consistently sustainable for most people, which of course it’s not. Most runners just take for granted that it’s normal and never consider that what they consider “easy” or “recovery” is in fact still too hard.
One of the reasons a runner’s aerobic development improves more quickly than their neuromuscular development is because running itself is very demanding. On both fronts you’re being pushed very hard. However, your aerobic and hormonal capacities bounce back much more quickly than your muscles, bones and joints.
Still, it’s incredibly stressful on your body chemistry to go that hard that often, and the fatigue can snowball too quickly for you to be able to handle a high volume of that kind of aerobic training.
In my cross training, I find I need to go pretty hard to get to Zone 1 in most heart rate training zone systems… somewhat too hard for the purposes of whatever cross training I’m doing. The level of effort require would leave me rather tired and possibly sore. This supposed recovery exercise ends up not helping me recover much at all.
It’s not that most runners are just stronger. They just spend all their lives in this perpetual fatigue, physical and adrenal. The long term effects on their health are taken for granted as aging or wear and tear, when in actuality it’s probably preventable… without compromising your fitness or development.
My most recent heart rate zones of choice were a standard 50/60/70/80/90/100 split based on the Karvonen Formula, which uses heart rate reserve. This is a function of your resting and max heart rates, and the zones are proportioned against those rates. Zone 1 for example would be 50-60% of the gap between your resting and max heart rate (your “heart rate reserve (HRR)”), zone 2 60-70% of the HRR, etc.
With a max HR of around 184 beats per minute, this sets my minimum training heart rate around 120 (depending on what my resting heart rate is at that time), with zone 1 peaking at about 130-135. This is about where most heart rate zone systems would put zone 1, and is considered a “recovery” heart rate.
On the spin bike, even at a brisk but easy effort, my heart rate is around 105-110. On the ARC Trainer I can get to 125-130, but only with a more moderate effort. On the rowing machine, a concerted effort typically gets me to about 110-120.
However, when running, I rarely can cruise at a heart rate below 130, no matter how slow and easy I run. I basically have to stop and walk/run to average a zone 1 heart rate. This is not a product of lacking fitness: Even at my peak condition and training in Chicago, it took the right combination of circumstances for me to average 125-130 at an easy effort.
All of this is to say that maybe our view of heart rate zones and “recovery zones” is a bit warped and could use an adjustment.
This is especially true in our coronavirus circumstances, where if we go to the gym (and in many cases train outside) we need to wear a mask while while exercising. We can’t huff and puff at full volume and expect max results if a mask is filtering much of the air taken in or expelled. I’ve talked before about this being a long term training benefit, but in the present it makes the effort required for aerobic training a bit too much.
Bear in mind as well that, to maintain the typical intensity for a full volume of training, you have to consume a lot of carbohydrates, which can cause a variety of inflammatory health problems if consumed in the large amounts that most endurance athletes tend to require.
One of the reasons low-carb diets tend not to work well for endurance athletes is because they train at an intensity where they need a lot of glycogen, and that can only come from and be replenished from a carbohydrate rich diet.
Could it be possible to scale back carb consumption to a more (shall I say) human level, rely more on slower fat burning, and still be able to train, perform, and develop at a high level.
I say yes, and I say the key to doing so is combining (now-)traditional 80/20 training principles with a revised approach to heart rate zones.
Instead of the Karvonen Formula, I’ll use the more conventional percentages of max heart rate for these zones.
Zone 1: Easy Aerobic – Recovery. 55-65% of max heart rate.
This is roughly a walk-level effort all the way to the low-end of what most would consider zone 1.
Pretty much all your cross training should take place in this zone. In most heart rate zone systems, this wouldn’t qualify as training intensity, falling below most’s definition of zone 1. But as far as I’m concerned, this qualifies as training.
Your aerobic capacity at this level would rely mostly on fat, with an insubstantial amount of glycogen utilized. The ratio of fat/glycogen usage at this range is anywhere from 4 to 1, down to 2 to 1.
As I mentioned, it’s difficult to impossible for most to run at this intensity. It’s purely a walking, cross training, strength training, or walk/run-mix zone for training. Most also vastly underestimate the aerobic benefit of workouts done at this range, just as they vastly overestimate the needless damage done at the more traditional training zones.
Zone 2: Aerobic Threshold. 65-75% of max heart rate.
This is what most training zone systems consider recovery and easy aerobic training. But for them, this would be zone 1. In my approach, this is actually zone 2, the higher end of most of your “easy runs”, and where most of your foundational base training should take place.
Here, you engage more of your glycogen stores, and the ratio of fat/glycogen usage at this range goes from 2/1 to about 55/45. This is ideal for some of your longer easy runs.
This is also the sweet spot for training in Phil Maffetone’s MAF approach, in which Maffetone advises never to exceed 75% of your max heart rate in aerobic training. This range is the high end of what he calls the Aerobic Threshold.
And for most runners, it’s also very hard to get themselves to run this easy. But unlike zone 1, many are able to actually run at this intensity once they’re trained to run regularly. This is the range at which most people should do all their easy runs.
This is also an easy range to accidentally exceed on an easy run. Many could tend to drift into the higher heart rate zone by accident. Training at zone 3 can feel easy, but in reality there is a bit of subsconscious strain taking place should you drift into zone 3.
Your heart rate reaching zone 3 during easy runs may also be a sign that you’re fatigued. You can always stop and walk/rest for a couple minutes to see if you normalize your heart rate, or perhaps your body needs more time to recover and you should cut the workout short.
Zone 3: Racing Strength. 75-85% of max heart rate.
Some coaches argue that this moderate to high aerobic intensity is a no-man’s land of training: Too hard to be easy, but not hard enough to reap optimal benefits. There is some merit to this argument, that you shouldn’t train here particularly often, any more than you’d train at a tempo or interval intensity, or strength train with heavy weights every single day with the same muscles.
This zone ranges from the aforementioned aerobic threshold, to a point comfortably below your likely lactate threshold. The max is akin to the high end of most other methods’ estimated marathon intensity, possibly the low end of their half-marathon intensity. Glycogen is utilized more here, from a fat/glycogen ratio of 55/45 to about 40/60, where once you reach the higher end more of your energy is coming from glycogen though you are still drawing a good portion of fat.
Honestly, the main purpose of running this intensity is that it’s the range at which you will run marathons, half-marathons, and similar long distance races. You train at zone 3 to train your body for the demand of running a goal race, more than to build aerobic fitness.
It goes back to the argument against tempo runs, that some believe you improve your lactate threshold and ability to race longer distances through high-low style training and alternating harder repeats with a high volume of easy running, rather than extended tempo runs.
My argument here is similar, that you don’t train at zone 3 to improve your aerobic fitness or VO2max, but to develop your neuromusuclar fitness for the goal race, what Brad Hudson labeled Specific Endurance in his book Run Faster. That label may be questionable in accuracy, since we tie endurance to aerobic capacity and this zone isn’t the best for aerobic improvement.
I am digressing a bit. This zone is akin to the Hanson Marathon Method‘s Tempo and Strength workouts, where they have you run at the intensity to develop familiarity with goal pace as well as the overall strength to run that pace for the needed time. Your aerobic capacity is to be developed in other workouts.
You train at zone 3 to improve your capacity for using existing aerobic and neuromuscular fitness over extended periods.
Zone 4: Running Economy and VO2max. 85-95% of max heart rate.
Zone 4 is the intensity you should hit on the back end of your 10K and 5K races. This is in line with where most methods would have you do tempo runs, longer cruise intervals, and repeats.
An aside: Because heart rate is a lagging indicator as you approach max effort, your heart rate should reach zone 4 only in later repeats of a speed workout, in an extended tempo effort, or in an actual race.
If doing zone 4 speed repeats, it’s generally more prudent to go by a pace or effort where you would eventually hit zone 4 if you maintained it for 10 minutes or more. So if you run a repeat at your 5K race pace or intensity and your heart rate never goes beyond zone 3 before your recovery interval, that’s okay.
The idea with the higher zones is more to gauge your desired intensity than to actually hit the heart rate itself. If nothing else, the zones should be more of a guide in races or longer tempo runs of whether your pace is acceptable, too much, could go faster, etc. (End aside)
Once you get into zones 4 and 5, most of your energy should come from glycogen, with very little to none coming from fat. The low end of zone 4 has a fat/glycogen ratio of 40/60, and the high end if well trained is around 30/70, though much of that fat burn could be recovery afterburn if running shorter speed repeats. That 30% comes more into play as an energy resource during extended tempo runs and races.
A good general guide of how to use your heart rates as a guide in zone 4:
85%: Half Marathon Intensity
90%: 10K Intensity
95%: 5K Intensity
Zone 5: Max Effort. 95-100% of max heart rate.
For any runner, zone 5 should only come into play if running a mile time trial, or perhaps the tail end of a really hard 5K effort. The intensity is similar to how you’d run hard 100-400 meter repeats where the goal is developing running economy, and you get long recovery breaks between each repeat.
At your absolute max, you could in theory get a fat/glycogen ratio of around 20/80. But this is not an intensity you could reasonably maintain for more than a few minutes, and whatever fat burn you get isn’t going to fuel your effort. Your zone 5 energy is all basically going to come from glycogen, and any fat burn will be afterburn in recovery as your body (and your breath) catches up.
Zone 5 is basically just your all out effort, within the scope of your running economy. The only time you’ll see a matching heart rate is when running a mile or perhaps the very end of a 5K, a situation where you’re going all out and your respiratory system simply cannot keep up.
As mentioned before, my interpretation of zone 5 and higher zones basically matches others’. It’s mostly the lower zones where I find a difference of opinion and results.
What do I do with this information?
Basically, when training easy, I would not train as hard as most do. I would train far easier than others would. I would set the heart rate training zones far lower than others would.
The hormonal and physical setbacks most experience after extended endurance training probably would not occur as severely if athletes trained at ranges more like I described than at the conventionally accepted heart rate zones. Most continuously overstress themselves, when that level of stress isn’t necessary to maximize aerobic and neuromuscular development.
I will get more into this over time, but I did want to share what I’ve developed regarding an improved approach to heart rate training zones.