The exercise addict’s soundbite, ‘no pain no gain’ turns out to be something of a big, fat lie. It seems that ‘no pain, a considerable raft of benefits’ is closer to the truth (although less catchy).

Welcome to Zone 2 cardio: gentle long runs, bike rides, even brisk walks that have almost mystical heart-building, fat-burning, life-enhancing properties. 

Something of a revelation to devotees of hard, intense exercise, Zone 2 is one of this year’s key fitness talking points. Influential US well-being podcasters such as Andrew Huberman and Dr Peter Attia have been recommending Zone 2 to their many thousands of listeners. As Huberman said on his podcast: “Getting 180-200 minutes of Zone 2 cardio per week has enormous positive effects on longevity and general health.”

Zone 2 cardio is linked to lower rates of a whole raft of diseases including type 2 diabetes, dementia, stroke and heart disease.

So what is Zone 2 training exactly?

Zone 2 training means exercising at a level of exertion where your body is working, but not very hard – at this level your body is able to use fat as fuel rather than carbohydrates. As you work harder and move up into Zone 3 and beyond you will switch to using carbohydrates, a quite different state in which your heart, lungs and muscles are under stress and will need time to recover. (You know this switch is happening when breathing becomes harder and you are gasping or panting.) 

Without plunging into a full physiology lecture, a Zone 2 workout takes place at this specific point of exertion and has a very positive effect on the metabolism, improving blood sugar levels and reducing insulin resistance. This is thanks to its turbocharging effect on our cells’ mitochondria.

Mitochondria are powerhouses in our cells that generate the energy we need for every action. Efficient mitochondria mean your body is better at converting fuel into energy, making you stronger and healthier.

Dr Richard Blagrove, senior lecturer in physiology at Loughborough University, says: “In terms of both health and performance, Zone 2 training can be really advantageous. I don’t feel bad about getting on my stationary bike and reading a book for an hour.”

He says elite athletes will be doing 90 per cent of their training in this way right now, laying down an “aerobic base” before they build to more intense modes of exercise for competition later in the year. For the rest of us, Zone 2 can be transformative.

Former professional cyclist and fitness coach at ATP Performance Andy Turner lost 24kg through this kind of movement. “Zone 2 makes you better at utilising fats as a fuel source and it can help level out your blood sugar. Longer-duration aerobics work can sometimes be forgotten, now it’s all about time-efficient, 30-minute, High-Intensity Interval Training (HIIT).”

HIIT cannot be done every day without strain and risk. It can take 48 hours or more for your body to recover from a session and unsurprisingly this does not speed up as you grow older, whereas Zone 2 provides its many benefits in a sustainable way. 

Zone 2 works best in a mix with some high-intensity training – three Zone 2 sessions a week with two HIIT blasts is a good mix.

How can you tell you’re in Zone 2?

Zone 1 is pretty much watching Antiques Roadshow in a favourite armchair; Zone 5 is being chased by a pack of slavering rabid dogs.

Zone 2 is the place where your body is working, but not very hard. Technically this is 60-70 per cent of your maximum heart rate, but an easier way to check is the Talk Test.

If you’re in Zone 2 you should be able to hold a fully realised conversation. If you were to call someone during a Zone 2 workout, you should be able to use complex sentences, not just sentiments such as “Help!” or “Taxi!”.

The point at which you reach Zone 2 will depend on your individual level of fitness. For those who are at the extreme end of sedentary, simply moving about the house performing chores can be a Zone 2 workout. The important thing is to keep going and not stray up into the zones that will put more stress on the body.

Each session needs to be sufficiently prolonged for the benefits to accrue. Experts recommend an hour to 90 minutes. The minimum time to feel the complete benefit of Zone 2 is 45 minutes. Research suggests less than this and you will not get the mitochondrial health you are hoping for.

It is, however, difficult to remain completely in control of your exertion for such a long stretch. I tried a 60-minute circuit of London’s Hampstead Heath on a glorious, blue-skied afternoon and found that either boredom or a hill would tempt me into more exertion. What was needed was a floaty, meditative approach to the run, an utterly different mindset to my usual goal-focused, gimlet-eyed determination.

If you find the idea of a mindful run too hippy, then locking a stationary bike or treadmill into the appropriate pace and watching a favourite film or settling into a book is a less “summer of love” approach.

There’s a misplaced, quasi-religious “sin” and “good works” element to fitness – we’re performing physical penance for modern life. Every slice of cake must be paid for in discomfort, making much of exercise a puritan cult. Running at Zone 2 pace in the park felt lazy and dented my middle-aged male pride. I wanted to stop passers-by and explain I was capable of more.

Zone 2 means letting go of the Personal Best obsession, but when you do, the reward is a calming, life-enhancing hour of your life with a rich array of health benefits. 

Antiques Roadshow, it turns out, runs to just about optimal Zone 2 duration. The universe is sending us a message.

Have you considered Zone 2 training? Please share your thoughts below