Lungs are amazing. There they sit, inflating and deflating from dawn to dusk, dusk to dawn, sucking in air, stripping out oxygen and exchanging it for carbon dioxide. They do this 20,000 times a day, 7.5m times a year, 600m times in the average lifetime, keeping our trillions of cells ticking over and saving them from choking on their own exhaust fumes. And we ignore them until something goes wrong and we’re gasping, wheezing, panicking – or worse.

When I think about lungs, it’s often in the same breath as cancer, which killed my dad 39 years ago. He only realised his lungs were knackered after a heart attack, which was probably also down to smoking. Sixty Senior Service a day, cigarette number two often lit as soon as number one was stubbed out. He stopped overnight, but it was too late.

I’ve never smoked, so I don’t worry much about lung cancer, and I don’t have asthma, or a persistent cough, or shortness of breath. But I still want to know how strong my lungs are. I’m 61, after all, and lung function begins to decline in your mid-30s. And it’s almost a year since I gave mine a proper workout, thanks to a knee injury. From running 30km or more a week, with a hard sprint to finish most sessions, I’m down to zero. In all, I’ve missed more than 100 hours of aerobic exercise.

But my knee is on the mend, after keyhole surgery to trim a torn meniscus, and today I’m going to push myself to the limit again. In a morning of tests at Sheffield Hallam University’s Advanced Wellbeing Research Centre, we’ve already measured my lungs’ capacity and general efficiency. That was a simple process called spirometry, which mostly comes down to blowing into a tube. Now I’m about to get on an exercise bike and pedal until I’m too out of breath to continue. I’ll have a mask strapped to my face, a heart rate monitor on my chest, someone to catch me if I faint and a bucket to hand in case I throw up.

“You’ll find it pretty unpleasant,” says Alex Bugg before picking up an enormous syringe. He’s a researcher at the university’s school of sport and physical activity. Before I have time to panic, Bugg explains that he’s only going to use the syringe to calibrate the equipment.

If you want to know how well your lungs (and heart) work under stress, this VO₂ max test is the best way to do it. The mask will measure the gases I’m breathing out, and hence how much oxygen my body can use when working flat out. You can get an estimate for VO₂ max from a smartwatch or other fitness tracker – but for complete accuracy you’ll need to do what I’m doing, or get masked up and run on a treadmill. If you take that option, you’ll usually be strapped into a harness, in case your legs give way.

I start off just spinning my legs against a slight resistance. Bugg tells me to find a comfortable cadence that I can maintain for as long as possible while he gradually increases the drag, from 50 watts to just over 300. So I pootle along at about 75 revolutions per minute, which feels like the kind of pace I’d hold if I was cycling unhurriedly on the flat. I don’t know my watts from my wazoo, but basic maths suggests that by the end of the test I’ll have to put in six times as much effort. Meanwhile, Bugg and a colleague will keep checking how I’m doing, holding up a chart where I can pick out my perceived rate of exertion.

“Six is complete rest,” he says, “while 20 would be an all-out sprint with nothing left to give. Towards the end, when you start to get a bit more breathless, feel free to point rather than speak.” He, in turn, will keep asking: “Happy to continue?” All I’ll have to do is nod, give a thumbs up or shake my head.

Let’s just get on with it, I think. Then, when we do, I wish we hadn’t. As the resistance increases, we’re soon in “somewhat hard” territory, then “hard”, “very hard”, “extremely hard”. My quads start burning and I switch to breathing through my mouth rather than my nose – at first silently, then in unhappy, ragged gasps. “We’re probably getting very close to your maximum now,” Bugg tells me 13 or 14 minutes in, as if I hadn’t already realised. When we hit it, at 253 watts, I let everyone know, not by saying so or pointing, but just … stopping. I don’t have any choice: however much I gasp for air, I can’t keep pushing. I’m done.

At least I didn’t faint or vomit. I even get off the bike without assistance.

We’ll get to the results in a minute, but if I wasn’t in this state-of-the-art lab, how would I know if I needed to worry about my lungs?

“If you can walk a couple of blocks or up two flights of stairs without getting breathless, you can exercise without getting fatigued easily, you do not complain of chest pain, cough or bring up sputum every day, you do not have blood in your phlegm, or wheeze, your lungs are probably all right,” says Dr Pallavi Periwal, an Indian pulmonologist and critical care physician, and the author of Make Every Breath Count. “Also look for signs like swelling of your feet, or curling-up of your nails, called clubbing. If any one of these or a combination of these symptoms are present, get yourself checked out.”

Don’t assume you’re in the clear just because you don’t smoke, she adds. “Yes, of course smoking’s a big risk factor as far as lungs go. But so is vaping and using a hookah, and secondhand smoke. Even if you do not smoke yourself, you could be a passive breather of poor air.”

Then there’s air pollution, indoors and out. “Check the air quality index before you go out, especially if you live in a city that is extremely polluted,” Periwal says. Use a face mask if necessary, and avoid exercising outdoors when the air quality is poor.

“If you can,” Asthma + Lung UK advises, “avoid pollution hotspots like main roads, junctions, bus stations and car parks. Try to use quieter back streets as much as possible or go out earlier before pollution levels increase.”

“Indoor air pollution is also something people do not think about,” Periwal says. “Things like mould, household chemicals, room fresheners, radon, burning candles and incense sticks can all affect indoor air quality. Ventilate your house frequently, dust and vacuum regularly, avoid chemicals with volatile organic compounds in your house, keep it smoke-free.”

Pets can cause problems too. Many of us are allergic to dog or cat fur without realising it, while bird droppings or feathers can bring on a condition called hypersensitivity pneumonitis.

In her own home, Periwal says, “I do not smoke, vape or allow any indoor smoke – no incense sticks or candles for me. I regularly dust and vacuum and ventilate my house. All bed linen, sheets, pillows are cleaned regularly. Kids’ soft toys are washed and dried regularly. These are big allergy triggers.”

At the risk of stating the obvious – but hey, it’s 2025 and there’s an anti-vaxxer running one of the world’s biggest healthcare systems – it’s also important to get vaccinated against common respiratory infections such as flu, especially if you fall into a high-risk group.

And what are the options if you need to strengthen your lungs?

“Exercising helps,” Periwal says. “Aerobic exercises like running, jogging and brisk walking improve your physical fitness and your body becomes more efficient in getting oxygen and transporting it to your muscles. Strength training builds core strength, improves posture and tones breathing muscles.”

These muscles matter because your lungs don’t inflate and deflate by themselves any more than a balloon does. That’s the work of your intercostal muscles (the ones between the ribs) and your diaphragm, the dome-shaped sheet of muscle that stretches beneath your chest. Strengthen these, and you strengthen your breathing. For patients with chronic lung problems, Periwal also recommends breathing exercises, particularly diaphragmatic breathing, sometimes known as abdominal or belly breathing, and pursed lip breathing, in which you inhale slowly through your nose and exhale gently through your – guess what? – pursed lips.

Doctors will sometimes prescribe inspiratory muscle training (IMT), AKA respiratory or ventilatory muscle training. I’ve been experimenting with a Powerbreathe trainer, available on the NHS if you have lung problems but also marketed to athletes wanting to improve performance. Twice a day, I take 30 short, sharp breaths, working against an adjustable resistance.

It feels as if I’m using the same muscles that I would at the end of a really hard workout, when I’m trying to suck in as much air as possible, as deeply as possible. “It’s a deep diaphragmatic belly breath,” says Dr Sabrina Brar, a former ear, nose and throat surgeon who is now a medical officer at Powerbreathe. “Some people get a sore tummy.”

Brar describes IMT as dumbbells for the lungs. It can be useful “if you are training to be an athlete or suffer from a lung condition”, Periwal agrees, “but learn the proper technique with a respiratory therapist. Do not overdo it.”

Anyway, my results. They’re not bad for an old man whose job is mostly arse-on-chair. “A healthy 60-year-old man can expect a VO₂ peak of 25-45ml/kg/min,” Bugg’s report reads. In other words, that healthy 60-year-old will consume 25-45 millilitres of oxygen per kilo of body weight per minute. A figure above 35ml/kg/min, meanwhile, suggests “a very good level of fitness”. Not good enough to earn you the maillot jaune, however: “Current Tour de France champion Tadej Pogačar has been reported to have a VO₂ max around 89.4ml/min/kg, meaning his body can use more than double the amount of oxygen during exercise compared with the average man.”

And me? My figure’s 41ml/kg/min. “Your VO₂ max is above average,” the report says, “and suggests a high level of fitness, and very efficient heart and lungs. Not only are your lungs in good health, but your body is well adapted to utilise the oxygen you breathe in and to dispose of the carbon dioxide waste product that accumulates during exercise.”

There’s a thumbs up from the spirometer too. “Overall, you have excellent lung function. You have above-average lung capacity, efficiency and power. There are no concerns that your lungs are obstructed or impaired in any way, and they can inhale and exhale as required.”

I’m tempted to preen until I remember Pogačar’s stats, and that Bryan Johnson, the 47-year-old squillionaire spending $2m a year so he can live for ever, claims he recorded a VO₂ max of 64.29. That, he says, is equal to “the top 1% of 18-year-olds”.

As for Bugg, 33, it’s eight years since he measured his VO₂ max, but back then it was an impressive 55. He’s currently training for a stair marathon. There are five floors in the Advanced Wellbeing Research Centre, and on 24 July he will be walking up and down them 227 times in aid of the Motor Neurone Disease Association. However good I feel about my lungs now, I don’t think I’ll be joining him.