Great article! I was raised in the 1980s ‘aerobic class’ era where ‘truly optimized’ aerobic activity was defined by the American Council on Exercise’s as involvement of all 5 major muscle groups simultaneously to produce best results.
I am retired so I have the time. I use the Morpheus system (Peter Attia interviewed the creator) which has only 3 zones. Zone 1 and 2 (blue zone) are compressed but users know the high end of the blue zone is more zone 2. The zone range changes based on recovery and resting heart rate for the day so it is a dynamic zone 2. I get my zone 2 via the rower but also walking after meals on a hill near my house. Average time is 30 minutes or so on those activities. Morpheus is a great system to track zone 2 or other zones.
The tutorial talks about how different exercises like cycling, running, rowing, etc will use different muscle fibers and the variety further increases mitochondrial gains.
Hi Chris, good article (as usual) and confirms what I've always suspected, that Zone 2 training isn't all it's cracked up to be. My unscientific mind thinks that if you're not pushing yourself, you're not making gains. I've tried zone 2 before but never felt that it improved my fitness.
I mainly focus on 2 types of workout: 1) aerobic HIIT where I seek to maintain 80-90%+ of my max HR through a combination of body-weight resistance (eg: pushups) and pure aerobic (eg: high knees) - and 2) pure resistance with hand weights which typically gets my HR to 50-60% of max HR. I do these 3-5 times a week for 30 minutes each session and on days that I'm feeling particularly fatigued or sore (usually once per week) I will do yoga or stretching which I think meets the definition of the "zone 2-type". I find that I'm constantly improving strength and endurance - at age 60 the progression is slow but steady.
In my experience, I get stronger and more toned and avoid injury when I do more strength/HIIT and don't overdo it on the easy miles (zone 2). The problem for me is I *love* long runs, haha. These days I do three days of running (including one long run), one day of lower-body focused HIIT and lifting, and one day of kickboxing (just the air, I don't have a bag) and upper body lifting and/or core. The other two days I do yoga. This way I satisfy my running habit while also being able to gain strength, put my body through different ranges of motion, and prevent overuse injuries from just running all the time. The higher intensity workouts are definitely more effective if you're pressed for time, and I enjoy them, too, but for me they are first and foremost a means to keep me out there on the trails consistently!
I like virtual riding in a group that paces between zone 2 and 3 when I can get miles in. I’ve been working in a 60 min sweet spot ride and some 60 min Z5+ interval repeats with my FTP scaling. However, I had to back-off to 90% of my FTP scaling for an over/unders which was Z5/Z4 over 13 min x2 (darn near a back to back 20 min FTP test workout). I don’t normally have back off that much, but I started lifting again and it fatigued me.
I have friends who are devotees of Inigo San Millan who did a cycling test on me where they tested my lactate with each 5 watt increase. They concluded from my lactate starting to increase at 105bpm to be indicative of a very poor aerobic base. I countered that I have never bonked at all distances up to the marathon where I missed the Boston qualifying time by less than 30 seconds due to a debilitating cramp that started at mile 11. And I am known as fast runner who can run any distance at any moment.
And did you know cyclist Podagar who dominated last years Tour De France dropped San Millan after coming in second in the 2023 TDF and trained with another coach for less than a year?! That told me San Millan does not have the trump card for optimal training strategies.
I think they kept it close to avoid making San Millan look bad since he’s still on Podagar’s team. You likely know that cycling teams are very secretive about their training and strategies.
Great post! I liked how you talked about working different muscle groups. However, the frequency and duration of your zone 2-ish workouts likely mean you miss out on low-hanging cardio adaptations, like increased stroke volume from cardiac hypertrophy in your left ventricle. Stroke volume correlates with gains in capillary development from endurance exercise.
Joel Jamieson points out that steady-state endurance can be used to accelerate recovery from more intense activity. He has a solid collection of athlete data in Morpheus backing up their recovery workouts and the amount of time recommended for recovery training each week.
Metabolically, I think Attia's advice to optimize individual maximal fat-burning zone (MFZ) is more critical than the threshold of zone 2. When the curve max moves to the right, it means the system as a whole is performing better. It's a useful performance metric based on lactic acid testing, but also, the increased mitochondrial capacity of MFZ accounts for gains in VO2 max capacity.
I liked this meta-study's metrics: 1) mitochondrial and 2) capillary growth. It finds the optimal weekly schedule for 2-3x endurance training, 2x high-intensity intervals, 1x sprint intervals, and rest between high-intensity days.
The 80% rule applies mostly to athletes with a training volume above that of the average population. I think the idea behind 'zone 2' , 'talk test', etc is to convey to the person trying to maintain decent fitness that a lot of workouts should not be very hard. (Plenty of messaging out there that every workout should be very difficult to get a benefit).
As you mentioned, lactate varies so much day to day based on diet, recovery, a million factors, using that as a zone 2 proxy is useless - but for an athlete with a high training volume, that 2.0 lactate threshold [effort] is where you want a lot of training to be, mostly as a way to get the maximum benefit from an 'easy day' but still recover between harder effort days.
Yes this all makes sense. It's just that one gets the impression from Attia that there is value to having a whole testing kit with jars of soapy and unsoapy water next to you so you can prick test every 15 minutes and it is somehow going to optimize your workout to make you live longer, and that's irrational based on the data showing how nebulous the boundaries are.
As rules of thumb these can be useful, but you need to be conscious that the thumbs are very fat.
Absolutely. I've never actually tested lactate during a 'zone 2' training session. That being said, when doing testing with lactate (workouts or a dedicated lactate curve test), it always lines up with what I'd perceive as that pace and effort, just as you said. Nothing magical about 1.7 vs 2.3
Do you have any thoughts on products like Bemitil, Mildronate or Cytoflavin? They all seem to improve my athletic conditioning. The first two are WADA banned so not surprising.
Cytoflavin supposedly “boosts ATP” Does the inosine and succinic acid in it play any role?
Thanks for the review of the research Chris, the linked studies are bizarrely eye-opening. Your thoughts also really resonate - e.g., why wouldn't training 10% under LT1 still give you 90% of the benefits? Or is it important that all tissues get into Z2 versus just the legs?
Andy Rowell linked a video from Steve Magness about zone 2 on your X account - https://x.com/AndyRowell/status/1900598012671324394 and I'd say Steve validates your points and provides good reasoning and context. Zone 2 is not just "undefinable" but also not really magical (on top of not being very practical).
Steve's content about endurance but also is really terrific because it imho shares similar qualities with what you create - he always tries to put things into a larger context (be it functional/physiological or historical), but he also geeks out on the technicalities and advanced concepts.
For example, his take on the 4x4 interval training method is my favorite because he reviews the original study where this method "won". It did indeed win but only barely over another method (7% vs 5% improvement in vo2max) and there were a bunch of other factors which made the study less useful than I believed after spending years in the online health space :)
For what it's worth, you mentioning the 60-minute duration of your workouts, it reminded me of the functional threshold power (FTP) used in cycling and the second lactate threshold in running - which are defined as the output that you can sustain for 60 minutes. And it's definitely a viable method of training, as far as I understand.
Zone 2, via Dr. Phil Maffetone's MAF ('maximum aerobic function') method, worked perfectly for me. Dr. Maffetone prescribes a primarily age-based formula for maximum heart rate during aerobic work: (180 minus age in years) beats per minute, with a few adjustments for health and fitness. For me, that was 180 - 60 + 5 = 125 bpm.
When I started MAF method training, I was just barely able to run 4.6 mph (0.5% incline) on a treadmill while keeping my heart rate no higher than 125 bpm. Within 18 months, I was up to 5.8 mph (0.5% incline) with the same heart rate, i.e., running 26% faster.
One of my annual benchmarks is the 'Freedom Four', a local four mile fun run on the 4th of July. Last year, at age 64, I ran my fastest time in that race in 17 years.
The MAF method did NOT work for my wife. She didn't improve at all. Turns out, she needs to exercise at a higher heart rate to get fitter. Contrary to Dr. Maffetone's claim, his one formula doesn't fit everyone.
And despite my success with the MAF method, if I were to train seriously for a 5k or longer running race, I would now target a much higher heart rate for the bulk of my endurance work [these days, my focus is more sprint oriented: baseball in the summer and speed skating in the winter]. This is based on using the NNOXX device -- https://www.nnoxx.com/nnoxx-one -- which continuously measures and displays both nitric oxide levels and muscle oxygen saturation (SmO2). It shows that I'm now able to maintain maximum SmO2 up to about 155 bpm, so that's where I'd target my longer duration workouts. ... I do credit the MAF method with getting me to this point; when I started MAF, I'm pretty sure my SmO2 would have started diving above 125 bpm.
From my experience, the NNOXX device is far superior to lactate testing to monitor workouts, both in practical terms -- continuous, non-invasive vs. intermittent, fiddly, expensive skin pricks -- and in terms of the value of the information towards training decisions/designs.
Brilliant breakdown. Love how you dismantled the false precision around Zone 2—feels like the fitness version of chasing macros with broken scales. Your shift to ‘Zone 2-style’ cardio that actually involves more of the body (like boxing + rowing) makes way more sense for real-world health. Bookmarking this for anyone obsessed with gadgets but missing the big picture. Bravo.
Sports specific training aside, why even bother with Zone 2 when you can pair resistance training high-intensity intervals? IMO, you cannot beat this tandem for overall and cardio health, as well as triggering longevity genes. I compete in Master's track & field sprint events, I'm muscular with just under 10% body fat, great cardio health. Unless I want to compete in endurance events, why bother with Zone 2. Don't need, period.
Great article! I was raised in the 1980s ‘aerobic class’ era where ‘truly optimized’ aerobic activity was defined by the American Council on Exercise’s as involvement of all 5 major muscle groups simultaneously to produce best results.
Burpees, jumping jacks, rowing, bear crawls, etc.
I am retired so I have the time. I use the Morpheus system (Peter Attia interviewed the creator) which has only 3 zones. Zone 1 and 2 (blue zone) are compressed but users know the high end of the blue zone is more zone 2. The zone range changes based on recovery and resting heart rate for the day so it is a dynamic zone 2. I get my zone 2 via the rower but also walking after meals on a hill near my house. Average time is 30 minutes or so on those activities. Morpheus is a great system to track zone 2 or other zones.
Morpheus is excellent. Joel Jamieson of Morpheus has a great free tutorial on steady state training and zone 2. https://trainwithmorpheus.com/topic/lesson-1-metabolic-health-and-performance/
The tutorial talks about how different exercises like cycling, running, rowing, etc will use different muscle fibers and the variety further increases mitochondrial gains.
Hi Chris, good article (as usual) and confirms what I've always suspected, that Zone 2 training isn't all it's cracked up to be. My unscientific mind thinks that if you're not pushing yourself, you're not making gains. I've tried zone 2 before but never felt that it improved my fitness.
I mainly focus on 2 types of workout: 1) aerobic HIIT where I seek to maintain 80-90%+ of my max HR through a combination of body-weight resistance (eg: pushups) and pure aerobic (eg: high knees) - and 2) pure resistance with hand weights which typically gets my HR to 50-60% of max HR. I do these 3-5 times a week for 30 minutes each session and on days that I'm feeling particularly fatigued or sore (usually once per week) I will do yoga or stretching which I think meets the definition of the "zone 2-type". I find that I'm constantly improving strength and endurance - at age 60 the progression is slow but steady.
Seems like variances in our abilities to buffer ph and use lacate could have something to do with the large variances in measurements
Very much agree simple things like talk test is much better than the other more nebulous ways to zone 2
Right but the talk test seems to put you in zone 3.
In my experience, I get stronger and more toned and avoid injury when I do more strength/HIIT and don't overdo it on the easy miles (zone 2). The problem for me is I *love* long runs, haha. These days I do three days of running (including one long run), one day of lower-body focused HIIT and lifting, and one day of kickboxing (just the air, I don't have a bag) and upper body lifting and/or core. The other two days I do yoga. This way I satisfy my running habit while also being able to gain strength, put my body through different ranges of motion, and prevent overuse injuries from just running all the time. The higher intensity workouts are definitely more effective if you're pressed for time, and I enjoy them, too, but for me they are first and foremost a means to keep me out there on the trails consistently!
Always appreciate your wealth of knowledge!
I respect you for being willing to change your mind.
As you continue to stay open minded in your research it helps all of us improve, too.
Thank you for your brilliant mind with an ego in check. Nice balance.
I like virtual riding in a group that paces between zone 2 and 3 when I can get miles in. I’ve been working in a 60 min sweet spot ride and some 60 min Z5+ interval repeats with my FTP scaling. However, I had to back-off to 90% of my FTP scaling for an over/unders which was Z5/Z4 over 13 min x2 (darn near a back to back 20 min FTP test workout). I don’t normally have back off that much, but I started lifting again and it fatigued me.
I have friends who are devotees of Inigo San Millan who did a cycling test on me where they tested my lactate with each 5 watt increase. They concluded from my lactate starting to increase at 105bpm to be indicative of a very poor aerobic base. I countered that I have never bonked at all distances up to the marathon where I missed the Boston qualifying time by less than 30 seconds due to a debilitating cramp that started at mile 11. And I am known as fast runner who can run any distance at any moment.
And did you know cyclist Podagar who dominated last years Tour De France dropped San Millan after coming in second in the 2023 TDF and trained with another coach for less than a year?! That told me San Millan does not have the trump card for optimal training strategies.
No can you link me to the Podagar story?
https://en.brujulabike.com/strength-heat-and-strategy-pogacars-master-plan-to-continue-improving-in-2025/
https://cyclinguptodate.com/cycling/last-year-tadej-was-dissatisfied-with-the-coach-analyst-tells-how-pogacars-improvement-mustve-been-due-to-change-in-coach
I think they kept it close to avoid making San Millan look bad since he’s still on Podagar’s team. You likely know that cycling teams are very secretive about their training and strategies.
Very interesting that the second article says he is doing more high-intensity work and strength training.
Yes very consistent with your recommendations! I was intrigued by the fact that most zone 2 training focuses on legs!
I will look!
So min effective does is to box or row for an hour every two weeks?
I try to do both at least once every 10 days.
Great post! I liked how you talked about working different muscle groups. However, the frequency and duration of your zone 2-ish workouts likely mean you miss out on low-hanging cardio adaptations, like increased stroke volume from cardiac hypertrophy in your left ventricle. Stroke volume correlates with gains in capillary development from endurance exercise.
Joel Jamieson points out that steady-state endurance can be used to accelerate recovery from more intense activity. He has a solid collection of athlete data in Morpheus backing up their recovery workouts and the amount of time recommended for recovery training each week.
Metabolically, I think Attia's advice to optimize individual maximal fat-burning zone (MFZ) is more critical than the threshold of zone 2. When the curve max moves to the right, it means the system as a whole is performing better. It's a useful performance metric based on lactic acid testing, but also, the increased mitochondrial capacity of MFZ accounts for gains in VO2 max capacity.
I liked this meta-study's metrics: 1) mitochondrial and 2) capillary growth. It finds the optimal weekly schedule for 2-3x endurance training, 2x high-intensity intervals, 1x sprint intervals, and rest between high-intensity days.
https://link.springer.com/article/10.1007/s40279-024-02120-2
Agreed that zone 2 is overhyped.
The 80% rule applies mostly to athletes with a training volume above that of the average population. I think the idea behind 'zone 2' , 'talk test', etc is to convey to the person trying to maintain decent fitness that a lot of workouts should not be very hard. (Plenty of messaging out there that every workout should be very difficult to get a benefit).
As you mentioned, lactate varies so much day to day based on diet, recovery, a million factors, using that as a zone 2 proxy is useless - but for an athlete with a high training volume, that 2.0 lactate threshold [effort] is where you want a lot of training to be, mostly as a way to get the maximum benefit from an 'easy day' but still recover between harder effort days.
Yes this all makes sense. It's just that one gets the impression from Attia that there is value to having a whole testing kit with jars of soapy and unsoapy water next to you so you can prick test every 15 minutes and it is somehow going to optimize your workout to make you live longer, and that's irrational based on the data showing how nebulous the boundaries are.
As rules of thumb these can be useful, but you need to be conscious that the thumbs are very fat.
Absolutely. I've never actually tested lactate during a 'zone 2' training session. That being said, when doing testing with lactate (workouts or a dedicated lactate curve test), it always lines up with what I'd perceive as that pace and effort, just as you said. Nothing magical about 1.7 vs 2.3
Do you have any thoughts on products like Bemitil, Mildronate or Cytoflavin? They all seem to improve my athletic conditioning. The first two are WADA banned so not surprising.
Cytoflavin supposedly “boosts ATP” Does the inosine and succinic acid in it play any role?
Thanks for the review of the research Chris, the linked studies are bizarrely eye-opening. Your thoughts also really resonate - e.g., why wouldn't training 10% under LT1 still give you 90% of the benefits? Or is it important that all tissues get into Z2 versus just the legs?
Andy Rowell linked a video from Steve Magness about zone 2 on your X account - https://x.com/AndyRowell/status/1900598012671324394 and I'd say Steve validates your points and provides good reasoning and context. Zone 2 is not just "undefinable" but also not really magical (on top of not being very practical).
Steve's content about endurance but also is really terrific because it imho shares similar qualities with what you create - he always tries to put things into a larger context (be it functional/physiological or historical), but he also geeks out on the technicalities and advanced concepts.
For example, his take on the 4x4 interval training method is my favorite because he reviews the original study where this method "won". It did indeed win but only barely over another method (7% vs 5% improvement in vo2max) and there were a bunch of other factors which made the study less useful than I believed after spending years in the online health space :)
For what it's worth, you mentioning the 60-minute duration of your workouts, it reminded me of the functional threshold power (FTP) used in cycling and the second lactate threshold in running - which are defined as the output that you can sustain for 60 minutes. And it's definitely a viable method of training, as far as I understand.
Zone 2, via Dr. Phil Maffetone's MAF ('maximum aerobic function') method, worked perfectly for me. Dr. Maffetone prescribes a primarily age-based formula for maximum heart rate during aerobic work: (180 minus age in years) beats per minute, with a few adjustments for health and fitness. For me, that was 180 - 60 + 5 = 125 bpm.
When I started MAF method training, I was just barely able to run 4.6 mph (0.5% incline) on a treadmill while keeping my heart rate no higher than 125 bpm. Within 18 months, I was up to 5.8 mph (0.5% incline) with the same heart rate, i.e., running 26% faster.
One of my annual benchmarks is the 'Freedom Four', a local four mile fun run on the 4th of July. Last year, at age 64, I ran my fastest time in that race in 17 years.
The MAF method did NOT work for my wife. She didn't improve at all. Turns out, she needs to exercise at a higher heart rate to get fitter. Contrary to Dr. Maffetone's claim, his one formula doesn't fit everyone.
And despite my success with the MAF method, if I were to train seriously for a 5k or longer running race, I would now target a much higher heart rate for the bulk of my endurance work [these days, my focus is more sprint oriented: baseball in the summer and speed skating in the winter]. This is based on using the NNOXX device -- https://www.nnoxx.com/nnoxx-one -- which continuously measures and displays both nitric oxide levels and muscle oxygen saturation (SmO2). It shows that I'm now able to maintain maximum SmO2 up to about 155 bpm, so that's where I'd target my longer duration workouts. ... I do credit the MAF method with getting me to this point; when I started MAF, I'm pretty sure my SmO2 would have started diving above 125 bpm.
From my experience, the NNOXX device is far superior to lactate testing to monitor workouts, both in practical terms -- continuous, non-invasive vs. intermittent, fiddly, expensive skin pricks -- and in terms of the value of the information towards training decisions/designs.
Brilliant breakdown. Love how you dismantled the false precision around Zone 2—feels like the fitness version of chasing macros with broken scales. Your shift to ‘Zone 2-style’ cardio that actually involves more of the body (like boxing + rowing) makes way more sense for real-world health. Bookmarking this for anyone obsessed with gadgets but missing the big picture. Bravo.
Sports specific training aside, why even bother with Zone 2 when you can pair resistance training high-intensity intervals? IMO, you cannot beat this tandem for overall and cardio health, as well as triggering longevity genes. I compete in Master's track & field sprint events, I'm muscular with just under 10% body fat, great cardio health. Unless I want to compete in endurance events, why bother with Zone 2. Don't need, period.