Zone 2 training for busy executives: what it is and what the evidence supports

Zone 2 training is steady, easy aerobic exercise, usually defined as 60 to 70 percent of your maximum heart rate, or a pace where you can still talk in full sentences. For a busy executive its main advantage is practical: it builds cardiorespiratory fitness, which a Cleveland Clinic study of 122,007 patients linked strongly to longer life, without the recovery cost of hard intervals. The evidence supports doing it consistently. It does not support treating it as a magic zone.

If you have spent any time around founders who train, you have heard zone 2 discussed with near-religious intensity. Long, slow sessions on the bike. Heart rate straps. Debates about lactate. Meanwhile, most executives are trying to figure out whether a 30-minute walk between calls counts for anything.

It does. This piece covers what zone 2 actually is, why fitness matters so much for people who run companies, what the research does and doesn't show, and how to fit it into a week that already feels full.

What is zone 2 training?

Heart rate zones are a way of dividing exercise intensity into bands, based on a percentage of your maximum heart rate. Harvard Health lays out a common five-zone model:

• Zone 1: 50 to 60 percent of maximum heart rate
• Zone 2: 60 to 70 percent
• Zone 3: 70 to 80 percent
• Zone 4: 80 to 90 percent
• Zone 5: 90 to 100 percent

Zone 2 sits at the easy end. Harvard describes it as an intensity where you can "speak in complete sentences." Cleveland Clinic exercise physiologist Christopher Travers puts it this way: "You're not going to feel like you're pushing it if you're exercising in zone 2. It should feel like a comfortable workout effort and something that you can do for a longer period of time."

That is the whole point. Zone 2 is the effort level you can sustain for a long time, repeat the next day and recover from without wrecking your sleep or your afternoon.

How do you estimate your zone 2 heart rate?

The standard rough estimate comes from the American Heart Association: "Your maximum heart rate is about 220 minus your age." For a 45-year-old, that gives an estimated maximum of 175 beats per minute. Zone 2 at 60 to 70 percent works out to roughly 105 to 123 beats per minute.

Treat that as a starting point. Age-based formulas are population averages, not measurements of your heart, and medications such as beta blockers change heart rate responses entirely. The AHA's own definition of moderate intensity is broader than the zone 2 band, at "about 50-70% of maximum heart rate."

This is why Harvard's expert, Kieran F. Reid of Harvard Medical School and Brigham and Women's Hospital, recommends rate of perceived exertion as "a simpler and equally effective way" to track workouts. If you can talk comfortably but would not want to sing, you are probably in the right place.

Why does cardiorespiratory fitness matter so much?

Zone 2 is a means. The end is cardiorespiratory fitness: how well your heart, lungs and muscles take in and use oxygen. And the data on fitness is some of the most striking in all of preventive medicine.

In 2018, Cleveland Clinic researchers published a study in JAMA Network Open that followed 122,007 patients who took treadmill exercise tests between 1991 and 2014. Over a median follow-up of 8.4 years, 13,637 of them died. The researchers sorted patients into fitness groups, from "low" (below the 25th percentile) to "elite" (at or above the 97.7th percentile).

The least fit patients had an adjusted hazard ratio for death of 5.04 compared with the most fit. The authors concluded that "cardiorespiratory fitness is inversely associated with long-term mortality with no observed upper limit of benefit."

Put that next to the risk factors executives already worry about, and the scale becomes clearer.

The comparison is not perfectly like for like. The fitness figure contrasts the two extremes of a spectrum, while smoking or diabetes is a yes-or-no factor. It is still a remarkable finding. The same study found that even the step from "high" to "elite" fitness was associated with lower mortality, with an adjusted hazard ratio of 0.77.

What this means at the scale of a career

A founder can easily spend a decade with a calendar that pushes fitness to the margins: early flights, investor dinners, a product launch that eats every weekend. The data suggests that fitness is one of the few levers that affects almost everything downstream. It also compounds, in both directions.

For someone who plans to lead for another 20 years, or to have a long and healthy life after an exit, low fitness is a quiet, large risk that rarely shows up on a board agenda.

Why zone 2 fits an executive's life

Most executives do not fail at exercise because they choose the wrong intensity. They fail because the plan does not survive contact with the calendar.

Zone 2 has three practical advantages.

Low recovery cost. Hard interval sessions are effective, but they are demanding. Do them on top of short sleep and a stressful week and you may feel worse, not better. Easy aerobic work is far more forgiving.

It can overlap with other things. A zone 2 session can be a brisk walk with a call on, an easy ride on a stationary bike while you listen to a board deck walkthrough, or a walking one-on-one with a direct report. You cannot run a hard interval while negotiating a term sheet. You can walk.

It is sustainable. Harvard's summary makes the point directly: "you don't need to train in zone 4 to reap the cardiovascular benefits of exercise. Consistent easy-to-moderate-intensity exercise is very effective."

What the evidence says, and what it doesn't

This is where the online enthusiasm and the research start to diverge.

Well established: Regular moderate-intensity aerobic activity is good for health, and national guidelines are built around it. The CDC says "Adults need 150 minutes of moderate-intensity physical activity a week," or "75 minutes of vigorous-intensity or an equivalent combination," plus "2 days of muscle-strengthening activity each week." Zone 2 falls within that moderate range.

Strong observational evidence: Higher cardiorespiratory fitness is associated with lower mortality, as the Cleveland Clinic study shows. That study is observational. It shows a strong association, not proof that raising your own fitness will change your individual risk by a specific amount.

Plausible but often overstated: Zone 2 is widely promoted as the "fat-burning zone." Harvard notes that a higher proportion of energy does come from fat at moderate intensities, but also that total energy expenditure matters more than fuel source for weight loss. Advocates also argue that zone 2 has special benefits for the mitochondria in your muscles. That is an active area of research, and claims that zone 2 is uniquely superior to other intensities for the general population go beyond what the evidence has settled.

Not supported: The idea that you need a lab test, a precise heart rate band or a particular device before easy cardio counts. Harvard's expert explicitly recommends perceived effort as an equally effective way to track training.

Higher intensity has its place. Cleveland Clinic notes that zones 3 to 5 can "push your fitness to higher levels." A sensible week for most executives includes mostly easy aerobic work, some harder efforts and strength training, rather than a single intensity treated as a cure-all.

If you have heart disease, chest pain or unexplained breathlessness with exertion, take medications that affect your heart rate, or have been sedentary for a long time, talk to your physician before starting a new training plan.

What a busy executive can do this week

You do not need a coach, a lab or a new device to start.

Audit the week you already have. Count the minutes of moderate activity you did last week. For many executives, the honest answer is well under 150. That number is your baseline.

Book two or three sessions like meetings. Thirty to forty-five minutes of easy walking, cycling or rowing, on the calendar, with the same protection you would give an investor call. Easy sessions are easier to keep.

Use the talk test. If you can speak in full sentences but are clearly working, you are close enough. If you can only get out a few words, back off.

Convert one meeting. A one-on-one or a phone call you would otherwise take at your desk can become a brisk walk. It adds minutes without adding hours.

Protect your sleep. Training adaptations happen during recovery. Our guide to meditation for sleep covers the wind-down side of this.

Add strength. The CDC's guidelines include two days of muscle strengthening each week. Zone 2 alone is not a complete program.

Where easy cardio and a calm mind overlap

Something interesting happens in a good zone 2 session. There is nothing to optimize, nothing to win, just steady breathing and repetition for 40 minutes. For many executives, it is the only part of the day when the mind is not pulled in six directions.

That is not a coincidence. Steady, sustainable effort and the capacity to stay present are related skills, and both help regulate a nervous system that spends much of the day on alert. Our piece on what chronic stress does to a founder's body looks at that system in more detail, and meditation for better decisions under pressure covers the attention side.

Training the other half of your stamina

Fitness is one kind of capacity. The ability to stay clear and regulated through a brutal quarter is another, and it can be trained just as deliberately. At Cinder, we work 1:1 with founders and executives on stress regulation, attention and recovery, the mental side of long-term performance.

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Sources

• Understanding exercise heart rate zones, Harvard Health Publishing, 2026
• What is zone 2 cardio?, Cleveland Clinic, 2025
• Target heart rates chart, American Heart Association, accessed 2026
• Association of cardiorespiratory fitness with long-term mortality among adults undergoing exercise treadmill testing, JAMA Network Open, 2018
• Adult activity: an overview, CDC, accessed 2026