Getting to Know the 5 Aerobic Work Zones
Written by Holden Rethwill
When we talk about aerobic exercise zones, what we are describing and measuring is the intensity at which your body is using its aerobic metabolism system to produce energy from fat and glycogen. By being able to understand and control what one you are training in, you are able to better target your needs whether they be recovery, fat loss, or to cover 100 miles in your upcoming race.
Let’s do a quick review of the 5 Aerobic Work Zones to give you a little background and theory on why your training plan should include workouts in all five zones, not just your favorite fun-zones.
Aerobic Work Zone 1
50-60% of Heart Rate Max
We also refer to this as the ‘recovery zone’. When training at this intensity, you should be able to easily carry on a conversation with your training partner. Zone 1 is basically your everyday living, walking around, not doing anything overly active.
Aerobic Work Zone 2
60-70% of Heart Rate Max
Let me just begin by saying…this is NOT the sexy stuff. It is not the Fran’s, the Isabel’s, the Jackie’s, etc. No…but Zone 2 work just might be what you’re missing in your road to physical awesomeness. (Read: Why Now is the Perfect Time to Fall in Love with Aerobic Zone 2 Training)
Think of it this way… what’s the strongest part of the tree, the trunk, or the branches? Let’s just say Zone 2 is the tree trunk to your aerobic ability, Fran is the acorns.
What is Aerobic Work Zone 2?
Zone 2 training is typically the lowest zone used for training purposes. Think of it as going for a jog while you can still hold a conversation – somewhere between 60-70% of your maximum heart rate. The purpose behind Zone 2 training is to be able to sustain a pace just below your aerobic threshold for 30+ minutes.
How to Calculate Zone 2 Threshold
Real quick.. A basic way from Phil Maffetone to calculate what that zone 2 upper threshold is as follows:
Step 1: Subtract your age from 180.
Step 2: Modify this number by selecting from the options below:
- If you have or are recovering from a major illness (heart disease, any operation or hospital stay, etc.), you’ve recently gone through a bout of chronic overtraining, or are on regular medication, subtract an additional 10.
- If your waist measurement is more than half of your height, subtract another 5.
- If you are injured, have regressed in training or competition, get more than two colds or bouts of flu per year, have allergies or asthma, or if you have been inconsistent or are just getting back into training, subtract an additional 5.
- If you have been training consistently (at least four times weekly) for up to two years without any of the problems just mentioned, keep the number (180–age) the same.
- If you have been training for more than two years without any of the problems listed above, and have made progress in competition without injury, add 5.
So now you know what that upper end of the threshold should be.
What are the benefits of Aerobic Work Zone 2?
Training in Zone 2 contributes to a number of things!!
- Higher cardiac output and lower resting heart rate!
- Increased VO2 max
- Increases the ability to sustain a higher percentage of your aerobic capacity without the build up of nasty lactic acid.
- Helps your body learn to use fat more efficiently as a fuel source, which then helps to preserve glycogen stores for use during bursts of higher intensity. (Also helps with body composition).
- Help to bring your body into a more parasympathetic state which in turn decreases your sympathetic drive and allows you to rest and recover more effectively.
- Increased endurance performance.
CrossFit is famous for high intensity training. And this isn’t saying that you shouldn’t continue to do so! Just saying that the benefits are clear that if you incorporate a little Zone 2 work into your training, all other facets can improve as well!
How to Incorporate Zone 2 Aerobic Training
Get you a little 30-60 minute aerobic session within that zone 2 threshold once or twice a week and see your cardio workouts improve vastly!
Aerobic Work Zone 3
70-80% of Heart Rate Max
We’re going to bump it up a level (literally) and talk about Zone 3 and the goodies surrounding that! Zone 3 is that level above zone 2 and below zone 4. That is all. Have a good day! Kidding…yes, of course that’s what it is…a bit of a gray zone. You tend to be at approximately a 7 out of 10 on the perceived exertion scale, and if you’re looking at it from a talking standpoint, you’re probably exercising at a pace where you can give just short 1-2 word answers. If you’re talking heart rate, we’re working at approximately 70-80% of your Max HR.
The reason many experts in endurance consider this the “dreaded gray zone” is because there’s evidence to suggest that you aren’t really getting a whole lot of benefit out of it, from a long endurance standpoint. You’re typically going too hard to get the benefits of Zone 2 (parasympathetic, general endurance, etc. if you forgot go back to yesterday’s email) AND you aren’t quite going at what would be considered a “race pace”, so you aren’t getting those benefits either.
Once you’ve bumped out of the Zone 2 pace and into Zone 3, you are starting to work above a comfortable aerobic pace, and are starting to create lactate response in your body, thus making recovery slower.
What are the benefits of Aerobic Work Zone 3?
Now, that said, there are some benefits to being in Zone 3, such as making more moderate efforts seem easier. i.e. If you run a 5k at a Zone 3 pace, the next time you run it at a Zone 2 pace it will feel even easier. Another benefit to being in Zone 3 is that it can help to improve your anaerobic threshold – meaning that you can gain the ability to workout at higher intensities for a longer amount of time.
When it boils down to it, just know the type of athlete that you are. If you’re someone who needs drastic improvement on aerobic capacity, then a little more Zone 2 work is recommended for you in conjunction with the typical Zone 4 and even 5 work that CrossFit tends to lead to. If you’re someone who’s an LSD guru – not the drug…long slow distance – yet you struggle with higher intensity workouts, it’s probably recommended you incorporate a little bit of Zone 3 work into your diet so as to improve your anaerobic threshold.
Regardless it is ok to train on occasion in Zone 3. It’s not going to hinder the progress of someone wanting to live a fit lifestyle (if you’re a marathon runner then you probably want to ignore all of this). Just know that I would not make this the majority of you’re training emphasis.
Aerobic Work Zone 4
80-90% of Heart Rate Max
We’ve crossed into “The Threshold Zone” where we get up to about 80-90% of our max heart rate. Most experts consider this a “race pace” zone and in this zone we’re looking at about an 8-9/10 on the rate of perceived exertion scale. Because of that level of effort, it is unlikely that you would be able to sustain this for any longer than 1 hour. Think 1 word answers while breathing heavily. You’ve now crossed over from aerobic work into beginning down the pathway of anaerobic work!
What are the benefits of Aerobic Work Zone 4?
- Your body will begin burning through carbohydrates rapidly in this zone
- You will boost your lactate threshold
- Zone 4 will teach the body to tolerate lactate better
- Training at a higher intensity helps to prepare for competition-type settings
- Zone 4 can help to boost your anaerobic capacity (the total amount of energy from the anaerobic (without oxygen) energy systems, that is the combined amount of output for the ATP, phospho-creatine and lactic acid systems)
- It utilizes more muscle fibers, which can help to build mitochondria in fast twitch fibers
- Your muscles will start to feel heavy and like you’re getting pretty pumped up when you reach this phase
How to Incorporate Zone 4 Aerobic Training
A great way to look at training zone 4 is to take a longer event…say a 3 mile run…and then breaking it down into faster intervals with a little bit of rest in between.
Sample Zone 4 Training Session
12 sets of:
400m run (at a faster pace than you would hold if you were running the 3 miles continuous)
Rest 1-2 minutes
Another great example…we’ve been doing a lot of 1:1 work:rest ratio training with the at-home workouts. You could pick a workout, we’ll just say running to make things easy…and do 15-20 sets of 1 minute run at a fast pace, and 1 minute rest in between sets.
At the end of the day, Zone 4 helps build up our ability to be anaerobic, which can be especially important in the sport of exercise. We still 100% recommend the majority of your training to be in a lower zone for aerobic capacity purposes, but being able to add some sessions in at a Zone 4 pace might just boost your abilities in the world of competitive exercise!
Aerobic Work Zone 5
90-100% of Heart Rate Max
The last of the zone’s will be talking about is the 5th and final zone. It is the point where you are at or just about to hit redline phase. Think of it this way.. if you can still speak, or see clearly, you’re not in Zone 5. When we hit zone 5 we’re looking at about a 10 or maybe even 11 on a scale of 1-10 when it comes to rate of perceived exertion. This zone is reserved for short bursts, think of it like Usain Bolt destroying everyone in the 100 or 200m dash. We have fully hit and passed lactate threshold and you will likely only be able to sustain this pace for a VERY short duration.
Here’s one: 40 seconds max calories on the Assault Bike. If that doesn’t leave you on the ground rethinking what the hell you just did, you didn’t reach Zone 5. Ever finish one of those and wonder why your legs won’t work? That’s because Zone 5 is purely lactic. You’re fully anaerobic in this phase and at this intensity massive amounts of lactic acid is getting pushed into your muscles that cannot be utilized. Eventually your muscles get so pumped that you are forced to slow down.
What are the benefits of Aerobic Work Zone 5?
To begin with, Zone 5 focuses primarily on maximum speed and output. Just like Zone 4, you are strengthening your muscles, increasing power, and building up mitochondria in your fast twitch muscles. This zone also trains our body to buffer or withstand high lactate acidosis, as well as teach it to re-synthesize lactic acid. In other words, training with high levels of lactic acid in your body teaches it to learn to adapt and buffer it out of your system.
How often should you train in Zone 5?
Most experts say that only 2-5% of your total training should be done in a Zone 5. But like I said, most of those experts are focused on marathons, tri-athletes, cyclists, and other endurance specialists. CrossFit is completely different, and so too could be whatever sport you’re partaking in. Examine this on a case by case basis and know that it will ebb and flow based on what you are currently focused on!
That said, we would not recommend anymore than 10% of your training come from this phase as it would make rest and recovery a complete nightmare. (If you haven’t guessed, Zone 5 is going to put you in a sympathetic – fight or flight – state for some time). Try blasting your legs on an Assault Bike sprint day after day after day and tell me if you’re getting any better…you won’t. Your body will not be able to recover fast enough, and there will be other health affects associated with being too often completely sympathetic.
Basically it comes down to this…we do CrossFit. Sometimes we hit that redline in a workout. Should we go there consistently? No. But, it’s ok to do it from time to time because you’re only teaching your body what it can do and what it needs to work on! Enjoy laying on the floor in a heap.