About Zone2AI

Zone2AI is a heart rate training app that tells people whether a workout was truly Zone 2, using all of their own health data instead of the age-based formula their watch uses. And what some watches call Zone 2 is not "real" Zone 2 (more on that later).

Zone2AI runs on iPhone with Apple Watch and with Garmin watches, and an Android version was submitted to Google Play in September 2026. Zone2AI was founded in 2025 by Rodrigo Sanchez-Rios and is published by Unbounded Technologies LLC from Medellín, Colombia. The first version reached the App Store on March 16, 2025. By September 2026 Zone2AI had been downloaded thousands of times and held a 4.5 star average across hundreds of App Store ratings in 33 countries.

Why Zone 2

"If you do one type of training for longevity, do Zone 2." That is Vassily Eliopoulos, MD, chief medical officer of Longevity Health, and his description of the zone is the plainest we know: the boring middle that builds the engine. Most people skip it, going either too easy, walking and texting, or too hard, intervals, classes, HIIT. In his words, it is not about burning more. It is about building capacity.

Real Zone 2 has a precise meaning. Peter Attia's team defines it as the highest effort you can hold without lactate building up in your blood: the point where your muscles still run mostly on fat, burned inside the mitochondria, the engines in every muscle cell. In practice you can hold a conversation, but you would rather not. Train there and the body answers by building more mitochondria and teaching them to burn fat for fuel. More mitochondria means more energy, even at rest, and the flexibility to switch between fat and glucose, which is why the crash after meals fades. Eliopoulos's tell: if you feel fit but still crash mid-afternoon, your mitochondria might be under-trained.

That capacity is measurable and it is a marker of health. In Iñigo San Millán's lab, elite endurance athletes clear lactate at four to four and a half watts per kilogram while metabolically ill people fall below one, and his 2023 review reports that improving mitochondrial function through Zone 2 improves insulin sensitivity and may reverse prediabetes.

The zone is narrow and personal, and this is where watches go wrong. Attia's team notes that Garmin, Polar and similar trackers define Zone 2 as 60 to 70 percent of maximum heart rate, which for most people sits below the effort that challenges the mitochondria, and the maximum itself is usually a guess from your age. Their verdict on those readouts: they can be ignored. Go a little too hard and you slide the other way into Zone 3, where lactate accumulates and, acting as a signal, shuts down fat burning. Both misses cost you the adaptation you came for. And a tracker that reports 40 percent of a workout in Zone 2 cannot tell you whether that was one continuous block or scattered minutes, which the research says are not the same stimulus. The benefit, as Eliopoulos puts it, is the duration, not the intensity. Resist the urge to push harder.

Two checks need no equipment: can you still hold a conversation, and, in Eliopoulos's version, can you breathe through your nose only. Zone2AI adds the third and keeps the record. It builds your range from the heart rate your body actually shows in your own workouts, your resting heart rate and your effort feedback after each session, the triangulation of heart rate and perceived exertion that Attia's team recommends for everyone without a lactate meter. Then it counts the minutes you spent continuously inside that range, warm-up excluded, and tells you whether the session counted.

How much: three sessions a week is enough to move the threshold and four or five is ideal. Beginners see gains from 20 to 30 minutes, and San Millán puts the minimum for trained people at 45 minutes with 60 to 90 as the goal. Eliopoulos lands in the same place: 150 to 180 minutes a week in three or four sessions of 45 to 60 minutes, walking on an incline, slow cycling, swimming or easy jogging, and the mode matters less than the consistency. Zone2AI's levels follow that ladder, from 15-minute sessions and 60 minutes a week at Level 1 to 75-minute sessions at Level 5.

Eliopoulos's signs you need more of it:

• You burn out easily after short efforts.
• You only train HIIT or heavy lifts.
• Your HRV is low.
• You crash after meals.
• You are fit but not energized.

The evidence behind real Zone 2 is unusually strong for something that costs nothing.

Zone 2 cardio reduces all-cause mortality more consistently than almost any drug ever studied. It is free. Nobody sells it.

150 minutes per week at a pace where you can hold a full conversation improves VO2 max, lowers resting heart rate, reduces fasting insulin, drops hs-CRP, and protects against cardiovascular disease, metabolic disease, and cognitive decline simultaneously. The effect size rivals statins. The cost is zero.

Vassily Eliopoulos, MD, co-founder and chief medical officer of Longevity Health, on Instagram, September 2026

His explanation for why no physician prescribes it: a Phase III trial costs $200 to $500 million, nothing about walking at a conversational pace can be patented, so the trial is never funded, the guideline is never written, and the most powerful tool stays outside the standard of care.

The peer-reviewed record points the same way. A 2013 study in the BMJ covering 305 randomised trials and 339,274 participants found exercise and drug interventions often similar in their mortality benefit for the secondary prevention of coronary heart disease, rehabilitation after stroke, heart failure and prediabetes (Naci and Ioannidis). A 2018 study of 122,007 adults in JAMA Network Open found cardiorespiratory fitness inversely associated with long-term mortality, with no upper limit to the benefit (Mandsager and colleagues).

The best longevity medicine is free, Eliopoulos says, and most people skip it. Zone 2 itself is free. What Zone2AI sells is the measurement: whether the hour you spent was inside your range, not near it. Zone2AI is a training tool, not a medical device, and it does not diagnose, treat or prevent any condition.

His bottom line is ours. You do not need to destroy yourself to improve energy. You need to train your mitochondria, and Zone 2 is how you do it.

Zone 2 Alone Is Not Enough

Attia's team names four pillars of exercise for the sport of life: stability, strength, aerobic efficiency, which is Zone 2, and peak aerobic output, which is VO2 max. They picture aerobic capacity as a triangle. Zone 2 widens the base, VO2 max raises the peak, and the area is what you get to spend in your later decades. In their words, if you want a high peak, you need a wide foundation. Eliopoulos adds the tiebreaker: both matter, and if you only have time for one, Zone 2 is the higher longevity yield. VO2 max is also the measure the JAMA study above tied most strongly to long-term mortality, and it falls roughly 10 percent a decade after 30 unless you push it. Pushing it takes short, hard efforts: the Norwegian 4x4, four minutes near your maximum, three minutes easy, four times, once or twice a week, on a base that can absorb it.

Zone2AI guides that sequence, and its progress card is that triangle. Each level sets a weekly Zone 2 goal, from 60 minutes a week at Level 1 to 75-minute sessions at Level 5. Every 180 minutes of real Zone 2 earns a sprint credit that unlocks a 4x4 session, and a 48 to 72 hour recovery gate holds the next one until your body is ready. The base earns the sprint, the sprint raises the peak, and the coach tells you which day is which. If you train both on one day, Zone 2 in the morning and the hard work later, or at least Zone 2 first, because the lactate from hard efforts lingers and blunts fat burning for the rest of a session.

Training is one part of a formula Eliopoulos states in one breath: three resistance sessions a week, two hours of Zone 2, one or two high-intensity sessions, protein forward, plant heavy, fiber adequate, processed food minimized. "It is not complicated. The complication is the noise around it." The peptides, the stem cells and the advanced diagnostics are, in his words, amplifiers, and you do not start with amplifiers. The founder's version, the one the coach keeps in view: sleep treated like a job, weights twice a week so the muscle stays with the engine, real food over processed food, and alcohol only when it is worth it. The research adds two details for the session itself. A carbohydrate-heavy meal before Zone 2 raises insulin and suppresses fat burning, so train fasted or after a low-carb meal, and drink water rather than sugary sports drinks. If you take a beta blocker or an asthma inhaler, heart rate stops being a reliable guide and your effort feedback carries more weight, which is one reason Zone2AI asks for it after every session. None of this is medical advice. It is the part of your health that is yours to run.

Sources: Birkenbach, Lipman and Attia, A guide to Zone 2 training, Peter Attia's newsletter, August 2024 · San Millán, The Key Role of Mitochondrial Function in Health and Disease, Antioxidants, 2023 · San Millán, Zone 2 training, TrainingPeaks.

What Zone2AI Does

A personal Zone 2 range

Zone2AI computes a Zone 2 heart rate range with the Karvonen heart rate reserve method from three inputs: the maximum heart rate observed in the person's own workouts, their resting heart rate, and their effort feedback after each session, which moves the range by about 1 percent per session within a 5 percent cap. The result is a range that fits one body, not an age group.

A verdict after every workout

Minutes after a workout saves, Zone2AI reports how many minutes were spent inside the range, with the warm-up excluded, and whether the session counted toward the week. The person learns whether the work happened, instead of reading an average heart rate that hides the hills and the flats.

An Apple Watch app

The Zone2AI watch app shows the personal range live during a session and marks time in and out of it, with the session mirrored on the iPhone lock screen. Zone 2 sessions and Norwegian 4x4 sprint sessions both run from the wrist.

A Garmin Connect IQ app

The Zone2AI Connect IQ app puts the same personal range on a Garmin watch and syncs each session back to the phone through Garmin Connect. More than half of Zone2AI users wear a Garmin, which makes this the app's most used watch lane.

An AI coach

Each day the coach writes one insight from the week's sessions, sleep and recovery signals, and answers questions about training in plain language. A thumbs up or down on each insight steers what the coach talks about next.

Five levels, weekly goals and sprint credits

Zone2AI sets a weekly Zone 2 goal by level, from 60 minutes a week at Level 1 to 75 minute sessions at Level 5, and Zone 2 minutes earn sprint credits that unlock 4x4 interval sessions. A Fitness Age reading tracks the trend over months.

What Makes Zone2AI Different

Measured numbers, not a 1970s formula

Apple's Heart Rate Zones and Garmin's default zones are percentages of a maximum heart rate estimated from age. Zone2AI uses the maximum heart rate observed in the person's own workouts plus their resting heart rate. For the founder, the gap was nine beats: the formula said 179, hill repeats said 188, and every zone moved with it.

A verdict, not a chart

Whoop, Athlytic and Training Today grade recovery and strain. Apple Fitness and Garmin Connect show time-in-zone bars. Zone2AI states whether a session counted and why, with the minutes inside the range set against the threshold for the person's level.

The watch you already own, and a price you can pay once

Whoop requires its own sensor band and a membership. Zone2AI runs on Apple Watch and on Garmin, with Android and Health Connect next, and offers a $39.99 lifetime purchase alongside the weekly and annual plans, so nobody is locked into a subscription to keep their range.

No account, no data resale

Zone2AI has no login and asks for no email. Health data stays on the device. Workout summaries travel transiently to Google Gemini only to write the text of an insight, and Zone2AI does not sell health data or share it with advertisers. The full detail is in the privacy policy.

One founder answers the mail

Support goes to support@zone2ai.com and the founder answers it himself, usually the same day. In App Store reviews he is named by about one in ten reviewers. Zone2AI shipped 57 App Store releases in its first 17 months, most of them built from user reports.

Who Uses Zone2AI

• People building an aerobic base for the long term, many of them following Peter Attia's or Iñigo San Millán's Zone 2 guidance.
• Garmin owners, who make up more than half of Zone2AI users and use the Connect IQ watch app.
• Apple Watch and Apple Watch Ultra owners who want a range built from their own numbers instead of Apple's age-based zones.
• Runners, cyclists, incline walkers and rowers who do steady cardio three to five times a week and want to know it counted.
• People returning to training after years away, who need a level that starts where they are and grows with them.

Numbers as of September 2026: thousands of downloads, a 4.5 star average across hundreds of App Store ratings in 33 countries, 57 releases in the first 17 months, and a user base where Garmin accounts for 57 percent of watches, Apple Watch 23 percent and Apple Watch Ultra 9 percent.

What Users Say

Public App Store reviews, quoted as written. Thousands of people have downloaded Zone2AI; these are five of the hundreds who left a rating.

The Team Behind Zone2AI

Rodrigo Sanchez-Rios, founder. Rodrigo is a 42 year old Mexican entrepreneur, born in San Diego, raised in Tijuana and based in Medellín, Colombia. He studied computer science at MIT and holds an MBA from Stanford. Before Zone2AI he worked in investment banking at Lehman Brothers and in private equity at Lindsay Goldberg in New York, co-founded La Haus, a Latin American real estate technology company that raised more than $200 million, and was a founding partner of Jaguar Capital, a real estate investment firm in Medellín. He is an Endeavor Entrepreneur and serves on the board of Endeavor Colombia. He loves reading science fiction, playing golf with his kids and discovering the best Mexican food with his wife.

Origin. At La Haus, Rodrigo worked alongside hundreds of engineers and software developers without writing code himself; he had not really coded since college. In 2025 he kept hearing about the new AI coding tools, Cursor among them, and started messing around with them on the one problem he wanted solved: after a year of believing his workouts were Zone 2, he had field-tested his maximum heart rate with hill repeats and found that his watch's formula had set his zones nine beats too low. Before he knew it, Zone2AI was on the App Store. The first version shipped on March 16, 2025.

Team. Zone2AI is founder-run. Rodrigo builds the app himself, ships the releases, and answers every support email and App Store review personally. The company is registered in Wyoming, United States, and operates from Medellín, Colombia. Follow him on X or LinkedIn.

I lost my mom and dad to diabetes and heart disease. Cancer runs in my family. For twenty years I did not take care of myself, focused on work. Then I turned 40, and with both of them gone I decided to change my life before my kids told the same story about me: Zone 2 most days, weights twice a week, sleep treated like a job, alcohol only when it is worth it. I built Zone2AI because the app I wanted did not exist, one that used my real numbers instead of a formula from the 1970s and told me straight whether a session counted.

In 2026, at 42, cancer found me anyway. Papillary thyroid cancer, surgery in May, treatment since. It does not change the thesis. It hardens it. This is not about beating cancer with cardio. My medical team handles the parts I cannot control. Zone 2 is the part of my health that is mine to run, and I run it every day.

To my three kids: I want to see you grow up. That is the whole game.

Rodrigo Sanchez-Rios, founder of Zone2AI

How Zone2AI Works

• Setup takes about five minutes and needs no account. The person picks their watch, grants Apple Health access on iPhone or connects Garmin, answers a few questions about age, training history and goals, and the range is computed in seconds.
• Every workout is analyzed automatically. Sessions arrive from Apple Health or Garmin Connect within minutes of saving. Zone2AI scores the minutes in range and sends a notification with the verdict, and a celebration when the weekly goal is met.
• The range lives on the wrist. The Zone2AI Apple Watch app and the Garmin Connect IQ app show the personal range live during a session.
• The coach is on the Home screen. One insight a day, plus Ask the Coach for questions about training, recovery and the numbers.
• Support is the founder. Email support@zone2ai.com. Replies usually land the same day. Billing runs through the App Store and Google Play, so plans are cancelled there.
• Releases ship most weeks. 57 App Store releases in the first 17 months, with release notes on the App Store listing.

Key Facts

Frequently Asked Questions