How do I know I’m in Zone Two?

As we covered in part one of this two-part series, zone two exercise is a metabolic state in which you’re producing maximum aerobic output while keeping blood lactate levels hovering just below the two mmol/L threshold. This can be determined by using a blood lactate measuring device that takes a sample of your blood via a finger prick and spits out your lactate level. 

Since being in a zone two state is defined by blood lactate this is a great way to monitor your exercise and ensure that you are indeed engaging in zone two. They also provide another layer of reliability since there are external factors that can unknowingly influence your lactate levels such as meal timing.

Although lactate devices are superior in the accuracy department, they’re expensive which makes them less accessible. In addition, they’re rather inconvenient since you must wash your hands with soap and water (not rubbing alcohol), prick your finger, and then read the output on the device all while maintaining the type of zone two exercise you’re engaged in.

Even if you decide to purchase a lactate device, you likely won’t use it to monitor every workout. Thankfully, there are convenient proxies you can use to gauge whether or not you’re in a zone two state.

Proxy #1: Heart Rate

Due to the relatively cheap cost and accessibility of heart rate monitoring watches and straps, this is a highly convenient method of determining your exercise zone. The key question lies in determining which method one should apply in calculating their zone two heart rate.

MAF 180

MAF 180, or maximum aerobic function 180, is a formula designed by Dr. Phil Maffetone to help individuals determine what their heart rate would be while exerting maximum aerobic power. Once determined, you can exercise at that heart rate with fairly high confidence you’re in zone two. Remember, max aerobic output is synonymous with zone two. It’s a state of exercise in which one is engaging solely type one muscle fibres, oxidizing fatty acids as energy, and maintaining lactate below two mmol/L.

To determine your unique MAF, subtract your age from 180 and then make any necessary modifications based on health and fitness needs. For example, if you’re 40 years old you would have a MAF starting point of 140 beats per minute (MAF = 180 – 40 years). From there, you can make any necessary tweaks based on the below criteria. Your post adjustment heart rate should provide a fairly accurate benchmark on which to base your zone two training.

True Max HR

Alternatively, if you know your true maximum heart rate you can take 78-81% of that number and begin training at that heart rate. You can then adjust based on your rating of perceived exertion during training sessions while keeping in mind that zone two is your all-day pace. So, if training at 81% of your true max heart rate feels like you’re overexerting yourself, adjust downwards by using a lower percentage. And vice versa. 

You can gauge perceived exertion based on your ability to nasal (nose) breathe. Zone two training should feel like you could breathe through your nose, but it would be uncomfortable to do so. When you get to the point where you feel like you need to open your mouth to maintain comfortability, you’re likely in zone two. You can use this nasal breathing test in combination with the talk test, explained below, to determine perceived exertion. 

It’s worth emphasizing here that this method is based on your true maximum heart rate, NOT an estimate or approximation. Do not use this proxy if you’re using the 220 minus your age formula or another method to estimate your maximum heart rate.

Proxy #2: The Talk Test

Similarly to using heart rate as a proxy, the talk test is also based on a rating of perceived exertion. In this case, determining whether you’re in zone two is based on the level of comfort you would feel in holding a conversation while exercising. In zone one, you could talk all day without discomfort. Once you move into zone two, you should feel like you could talk but it would be uncomfortable or annoying to do so. 

In other words, you’re exercising at a level where you could carry on a conversation but it would be a little bit of a strain. If you can maintain a steady state of exercise sitting at this threshold right before you can no longer carry on a conversation, you’re likely in Zone 2. If you were on the phone, the person on the other end would be able to tell you’re exercising!

Proxies Summarized

Whether you decide to invest in a lactate device for regular spot checks or rely on using a combination of these proxies, remember that zone two is your all-day pace. You should feel like you could keep going all day without relent if you needed to. You should be able to maintain a conversation, but feel slightly uncomfortable, annoyed, or strained while doing so. The same applies to comfortability, or lack thereof, in nasal breathing. Run these cues through your head as you engage in aerobic exercise and you can proceed with confidence that you’re indeed in a zone two state.

Zone Two Training Protocol

Environment Matters

Zone two training is often viewed through the lens of an exercise prescription that if done correctly and consistently, can have a profound positive impact on the overall length of our lives.

Because you can easily slip out of a zone two state by either exercising too intensely or not intensely enough, it’s important to maintain as much control as possible. This is critical since the overall effectiveness of this training is predicated on our ability to remain in a zone two metabolic state for the entirety of a session.

There’s a difference between having been in a zone two state for 45 minutes out of a 60-minute run in which your heart rate was constantly fluctuating up and down versus having been in a zone two state for 45 minutes straight. Although the total time you were in zone two is the same, the metabolic benefits derived are not equivalent. There are of course benefits to up and down heart rate exercise, but for the type of mitochondrial training we’re focusing on here, you want to stay in a zone two state the entire time. 

One’s ability to remain in a consistent physiological state is drastically reduced when they surrender the control that comes with exercising indoors on a treadmill, stationary bike, or another device in which you can set the cadence and resistance to outdoor exercise. For that reason, the forms of exercise suggested here will be geared towards indoor, stationary machines with which you can accurately dial in your output to ensure you’re in a zone two metabolic state. 

People that’ll say, “Hey, I went out and ran today and my app told me I spent 30 minutes in zone two.” And it’s like, “Well, that’s not the same because if you’re going up and down and up and down and up and down, yes, the area under the curve is 30 minutes, but that’s not the same as spending 30 straight minutes in it.” – Dr. Peter Attia

The Protocol

“You can accomplish very important mitochondrial adaptations and very important metabolic adaptations by exercising one hour.” — Iñigo San-Millán

The zone two protocol you adhere to will be largely dependent on your starting fitness level and the amount of time you have available. This form of low-intensity aerobic training is only one pillar of four under the lever of exercise which is important to keep in mind as you structure a well-rounded regimen that suits your lifestyle. A table with one leg isn’t much of a table. It needs all four (aerobic, anaerobic, strength, stability/flexibility/mobility) to hold up against the test of time!

Aim for three to six sessions per week ranging from 20 to 90 minutes in length. This is an extremely variable range since everyone will have a unique starting point based on their current fitness levels. It’s also worth thinking about how you can best work with yourself to maximize habit adoption. Maybe you’re in great shape but want to start and build up slowly to ensure you form a consistent habit of zone two training. 

The goal is to work towards four to six sessions per week each lasting 60-90 minutes in duration. We’re aiming for a minimum of three to four hours per week spent in a zone two state with sessions lasting no less than 45 minutes, but the more you do the better. For example, six 90-minute long sessions per week will return better results than four 60-minute sessions.

However, many will not have the time or admiration to spend this much time performing this one type of training. If you want to minimize the amount of time you spend training in zone two while maximizing results, the minimum effective dose is four sessions that are 45 minutes in duration per week, totaling three hours. 

Once you work up to at least four 45-60 minute sessions per week, you can maintain. Eventually, your hard work will pay off and you will become more metabolically efficient. In other words, you will be able to produce more output at the same lactate and heart rate levels. This means you will need to increase variables such as your cadence or resistance in order to find your new and improved zone two state. 

Shortform: The Z2 Protocol

• Frequency: 3–6 sessions per week.

• Duration: 45–90 minutes in duration per session.

  • More is probably better, but going much beyond the MED will start to return diminishing marginal improvements.

  • Depending on your fitness levels, you may choose to start with 20-minute sessions and work up from there.

• Minimum Effective Dose (MED):  four 45-minute sessions per week.

• Comparing Protocols: Due to higher frequency, a regimen of four 60-minute sessions per week trumps two 120-minute sessions, one 240-minute session, or one 80-minute session combined with 3 shorter sessions. 

Choose Your Weapon

Since you can control the cadence and resistance of stationary exercise, it’s preferred over outdoor activity for the type of prescriptive zone two aerobic training we’re focusing on. It’s also worth noting that your background or experience with a particular movement will heavily impact your efficiency on that machine. For example, if you have experience as a rower you will be much more efficient on a rowing machine than on a stationary bicycle. 

This may impact your ability to maintain a zone two state in a given form of exercise, especially for those in which form is pivotal to your performance such as rowing. Keep this in mind as you may want to spend some time researching and learning about proper form before jumping in to minimize risk of injury and ensure you’re efficient enough to stay in a zone two state. I recommend starting with the form of aerobic exercise that’s most comfortable for you. 

Stationary Bicycle

You can use a stationary bicycle such as a Peloton or those contained in any gym which allows you to set the resistance level. From there you can adjust your cadence, or how fast you’re pedaling, to find your unique zone two wattage, a metric commonly used to measure cycling output. 

If the bike you’re using doesn’t display wattage, find another useful marker such as pace which will be denoted in some combination of time (minutes or hours) and distance (kilometers or miles). After taking the time to find your zone two output, you can exercise at that output in future sessions until you have improved to a point where you are below a zone two state while cycling at that intensity.

This means you have adapted and need to increase your output. Repeat this cycle of playing with cadence and resistance to find your new zone two state.

Alternatively, if you have a road bike you can purchase a device such as a Wahoo KICKR which allows you to indicate the number of watts you want to produce after which it sets the resistance for you. This takes the thinking and effort out of it as once you find your initial zone two wattage you don’t need to make any adjustments until you notice an improvement in your fitness level. 

You can check out this video of Dr. Peter Attia using his Wahoo Kickr and explaining his zone two workout on Instagram.

Treadmill

Using a treadmill is another great option. Since running will take most people above zone two, brisk incline walking is generally a better place to start. Start with a 10-15 degree incline at 2.5-3.0 miles per hour and use the proxies above to increase or decrease the speed and/or incline until you find your zone two.

Once you figure out the perfect combination of incline and speed, you can set it and forget it for future workouts. Just as with cycling, there’s no need to change your output until you notice improved fitness levels that indicate you’re no longer in zone two while exercising at a certain speed and incline. 

If you’re an experienced runner you may be able to hold a zone two state while running on a treadmill or even outside if you’re knowledgeable and meticulous about maintaining consistent output in which lactate levels are below two mmol/L as indicated by a blood finger prick or the use of proxies.

Rowing Machine

Rowing is a great option for zone five training which was introduced here. However, it may be difficult to maintain a zone two state unless you’re an extremely experienced rower with a mastery of the technique. Those who aren’t proficient rowers often fail in their form before achieving the metabolic benefits associated with zone two aerobic training.

If you don’t have a rowing background, start zone two training with another method and practice rowing technique during zone five or other interval training. With practice and conditioning, you’ll be able to use rowing as your primary form of zone two exercise.  

As an aside, rowing is a fantastic whole-body exercise. Executing a row with proper technique requires whole-body coordination and involves both a hip hinge and a row. The utility of this movement translates into many other everyday aspects of life and covers two (hip hinge and pull) of the four (hip hinge, pull, push, and squat) strength movements.

I encourage you to integrate rowing into your exercise routine, whether it be used for zone two aerobic or higher intensity anaerobic exercise. But before you start, take the time to master the form, or you’ll run the risk of injury. 

Stairmaster

The Stairmaster, which is effectively a rolling staircase, is another great option for both zone two and zone five exercise. The only caution I advise is based on my anecdotal experience of seeing people I know aggravate or worsen knee injuries by using the Stairmaster.

This is solely based on what I’ve seen in those around me so don’t shy away from using the Stairmaster if it’s your preference. However, if something starts to feel off then stop immediately. Speaking from experience, there’s no pride in worsening an injury just to finish a session. 

Elliptical

The elliptical is another option, however, it’s much easier to slip in and out of a zone two state on this machine. Since maintaining this consistent metabolic state for the entirety of a session is where the benefits are derived from this form of exercise, the elliptical is a suboptimal method for most people.   

Optimization Station

If you’re looking to further enhance the benefits of zone two exercise, you may consider performing this aerobic training in a fasted state. Dr. Peter Attia is a proponent of doing this as being in a fasted state provides the maximum energy substrate, or fatty acids and glucose, available for the muscles. 

Maximizing the availability of fatty acids, which is the energy substrate we utilize in zone two, can be done by minimizing insulin levels since insulin impairs lipolysis. Insulin is primarily secreted when we consume glucose (carbohydrates) so being in a fasted state ensures minimal insulin levels. 

Additionally, Peter has noticed that the higher his glucose levels during a zone two session, the higher his lactate levels will be. This means that to maintain a zone two state (lactate < 2 mmol/L) he will need to produce a lower output. Anecdotally, this is another reason to perform this exercise in a fasted state: fasted state → lower blood glucose levels → lower lactate levels during zone two exercise → higher output exerted over the duration of the session.  

Onwards and Upwards

Zone two aerobic exercise has been proven to be one of the most effective forms of exercise we can engage in to drive down our risk of mortality. The best part of it is that less is more.

You don’t need to go out there and feel like you’re going to collapse each time you perform aerobic exercise. Ironically, you’re actually achieving less of the beneficial metabolic adaptations that way. There’s a time and a place for exerting maximal effort in training, but it’s not here. 

By exercising at your all-day pace, measured by the proxies above, for a total of three to four hours per week in sessions of 45-60 minutes in length, you can drastically improve your metabolic health, mitochondrial efficiency, and lower your overall risk of mortality. 

Get out there, find your zone two pace, and hold it for an hour or so a few times per week. Once you find your flow, I bet you’ll even enjoy it!

Share Longevity Minded

And, as always, please give me feedback on Instagram or by hitting reply to this email.

Much love,

Jack