Why Your Easy Runs Are Too Hard

Most easy runs aren’t easy. Left to choose their own intensity, most people settle close to their ventilatory or lactate threshold, the point where breathing and effort start to climb, and training that’s meant to be easy tends to creep a little harder than intended. That puts the pace most of us drift into at the top edge of zone 2, or past it.

Zone 2 is the fix, and also one of the most over-sold ideas in fitness right now. Strip the hype away and it’s easy aerobic exercise: an effort you can keep up for a long time while talking in full sentences. It’s worth doing for a plain reason. It lets you run more, and more often, without flattening the rest of your week.

Below, we show four ways to find your zone 2, with the arithmetic worked for four example runners. Then comes an eight-week block to practise it on: the Base Building Run Block from Cinder, the workout tracker we make, with three to five runs a week and not a single hard session. After the plan, we look at what the research says zone 2 does and doesn’t do.

What is zone 2 training?

“Zone 2” comes from five-zone heart-rate charts, and different charts draw the lines in different places. The definition worth using is the physiological one. In 2025 a panel of 14 sport scientists and coaches agreed that zone 2 training should sit immediately below the first lactate or ventilatory threshold: the point where lactate starts to build in your blood and your breathing picks up enough that talking stops being effortless.

One trap when you read the research: many studies use a three-zone model instead. There, zone 1 is everything below that first threshold, and zone 2 is the band between the first and second thresholds, where tempo runs live. So when a study reports that elite athletes train surprisingly little at threshold, it’s talking about that middle band. The zone 2 people talk about online sits inside the research’s zone 1.

How to calculate your zone 2 heart rate

There are four common ways, plus the zones your Apple Watch sets for you. They won’t give the same answer, and knowing why is most of the battle.

1. A percentage of your max heart rate

The simplest version estimates your max heart rate as 220 minus your age and calls 60 to 70% of it zone 2. That’s the chart Cleveland Clinic uses, and you can do it in your head. It isn’t universal, though. Another widely used five-zone model, common in cycling, puts zone 2 at about 72 to 82% of max, which tells you how loosely the term gets used.

The weak link is the max. Age formulas describe the average person your age. A better one, 208 − 0.7 × age, comes from a meta-analysis of 351 studies and 18,712 people (it’s usually called the Tanaka formula, after its first author), and it’s still a population line. In a Norwegian study of 3,320 healthy adults, age alone predicted max heart rate with a standard error of 10.8 beats a minute, and a US lab comparison of the common formulas found poor agreement with measured max for every one of them. For any one person, a formula max can easily be 10 or more beats too high or too low.

2. A percentage of your heart-rate reserve (the Karvonen method)

Heart-rate reserve is the gap between your resting and maximum heart rate. The Karvonen method takes a percentage of that gap and adds your resting heart rate back on:

Zone 2 = resting HR + (0.6 to 0.7) × (max HR − resting HR)

It’s built on two of your numbers instead of one, and there’s a physiological reason to like it. In a study of 63 adults, percentage of heart-rate reserve tracked percentage of oxygen-uptake reserve almost one for one, and oxygen-uptake reserve is a direct measure of how much of your aerobic range you’re using.

This is the method Cinder uses: five zones split at 60, 70, 80 and 90% of heart-rate reserve, so zone 2 is 60 to 70%. The inputs decide everything, so here’s where they come from. Resting heart rate is the average of your resting readings in Apple Health over the last 60 days (or your most recent reading, or 60 bpm if Health has none). Max heart rate starts as the Tanaka estimate, but only until your workouts say otherwise. Cinder raises it to the highest heart rate you’ve actually reached, using a high percentile of each workout’s readings so one glitchy spike can’t set it, or to the max implied by a long effort you’ve held. It assumes nobody sustains more than 85% of their reserve for 40 to 75 minutes, so averaging 160 bpm for a 50-minute run with a resting rate of 60 implies a max of at least 178. Settings shows the resting and max figures in use, and where the max came from.

3. Your first threshold, measured in a lab

The accurate way to find zone 2 is to measure it. A lab or sports-medicine clinic can find your first threshold with blood lactate samples or breathing-gas analysis during a step test, and your zone 2 heart rate sits just below it. The reason it matters is how much people differ. In a 2025 study of 50 trained cyclists, the first ventilatory threshold averaged 81% of max heart rate, give or take about 4 points, and the fixed percentages of max and fixed lactate values often used to set zone 2 varied widely from rider to rider. The authors point out that a 5% miss on a heart-rate target is roughly 10 beats a minute.

Most people won’t get tested, and that’s fine. Treat the threshold as the thing the other methods are all trying to estimate.

4. The talk test

No numbers needed. Mid-run, say a couple of sentences out loud, or recite something you know by heart. In a lab study that ran the talk test alongside gas analysis on a treadmill and a bike, the point where speech first became difficult was almost exactly the ventilatory threshold, and when talking wasn’t comfortable, people were consistently above it. A review in a cardiology journal found the test valid, reliable and consistent across walking, jogging and cycling, in athletes, healthy adults and people with heart disease.

So: if you can talk in full sentences comfortably, you’re in zone 2 or below. If talking starts to feel not quite comfortable, you’re at the top edge. If you’re down to a few words at a time, you’re above it, whatever colour the watch shows. On the 6-to-20 scale of perceived effort, the first threshold sits around 10 to 11.

What about Apple Watch heart rate zones?

The Workout app sets five zones for you. Apple describes them as a percentage of your maximum heart rate, calculated automatically from your Health data, and they only appear once your date of birth is in the Health app. Apple’s guide doesn’t give the exact percentages. You can override them: on the watch, open Settings, go to Workout > Heart Rate Zones, tap Manual, and enter lower and upper limits for zones 2, 3 and 4. The Watch app on your iPhone has the same setting under My Watch > Workout > Heart Rate Zones.

So the Workout app, a percentage-of-max chart and a reserve-based app can each show a different zone 2 for the same run. None of them is wrong on its own terms; they use different definitions. If you want your watch to match the reserve method, work out your numbers from the table below and enter them as the Workout app’s manual zone 2.

Zone 2 heart rate by age: four worked examples

Here’s what the two formulas give for four example runners, each with a stated resting heart rate. To compare like with like, both zone 2 columns start from the same estimated max (the Tanaka formula, rounded to a whole beat), so the only difference is the method. All figures are in beats per minute.

The arithmetic, once, for the 35-year-old:

1. Estimated max: 208 − 0.7 × 35 = 183.5, rounded to 184.
2. Heart-rate reserve: 184 − 62 = 122.
3. Bottom of zone 2: 62 + 0.6 × 122 = 135.2, so about 135.
4. Top of zone 2: 62 + 0.7 × 122 = 147.4, so about 147.
5. For comparison, 60 to 70% of max is 0.6 × 184 = 110 up to 0.7 × 184 = 129.

The same “60 to 70%” gives two zones roughly 20 beats apart, because the reserve method adds your resting heart rate back on. Run at 147 bpm, the top of this runner’s reserve-based zone 2, and a percentage-of-max chart calls it zone 3 (70 to 80% of 184 is 129 to 147).

Now the caveat that matters more than any row in that table. Every number in it leans on a formula max, and a formula max is a population average that can be 10 or more beats off for you. If this 35-year-old’s real max is 194, their reserve-based zone 2 moves up to about 141 to 154. If it’s 174, the zone drops to about 129 to 140. A 10-beat error in max shifts the whole zone by 6 or 7 beats. That’s the reason to trust a max you’ve actually recorded over a formula, and to keep the talk test running alongside whatever number you use.

Which method should you use?

Our take: use heart-rate reserve if you know your resting heart rate, check it against the talk test in your first week, and when the two disagree, believe your breathing. If the number says zone 2 but you can’t finish a sentence, slow down. If you’re chatting easily and the number says zone 3, your estimated max may be too low, or it’s hot, or you’re late in a long run (more on drift in the plan notes). A lab test settles it if you want certainty.

The plan: who it’s for and how it works

The Base Building Run Block is, in the app’s own words, “an eight week block with no hard sessions at all”. Its description says it “suits someone between goals who wants steady, unhurried volume, or someone coming back after time off who would rather rebuild than race.” It’s labelled beginner because nothing in it is hard, but it isn’t a start-from-zero plan: week 1 has a 30-minute run and a 55-minute long run. If half an hour of easy running is still a stretch, build up to it first with a walk-run plan.

• Every session is easy. The only speed in the plan is six 20-second strides at the end of one run, about two minutes of quick running a week.
• Only the long run grows. It starts at 55 minutes, reaches 82½ in week 7, and steps back in weeks 4 and 8. The other runs stay at 30, 25 and 35 minutes, and the optional ride at 40, for all eight weeks.
• Pick three, four or five days. With five, you get everything. With four, the optional Easy Spin drops out; with three, the strides go too. The long run always stays, always lands on your last training day, and is never the day after the strides.
• No pace targets. Run each session by heart rate or the talk test. Your pace is whatever easy happens to be that day.