Like me, you’ve probably always taken comfort in numbers. Kilometres run, kilos lifted, VO₂max on a lab printout – for years I treated those figures like a fitness bank balance. In some ways I still do.

But there’s a catch. Number like VO₂max tells you how efficiently your heart, lungs and muscles use oxygen, or cardiorespiratory fitness in short; it doesn’t tell you how well you sleep, how happy you are or whether you’ll show up again next week. VO2 Max and longevity are not directly correlated, that is clear.

A recent essay by sports scientist Marc Pasqués points out that longevity depends on much more than cardiovascular fitness: metabolic health, mental wellbeing, genetics and lifestyle habits all play roles. Focusing solely on VO₂max and longevity can even encourage high‑intensity training at the expense of balance and injury risk. In other words, chasing a bigger number may ignore the parts of life that really keep you alive.

The latest science shows that enjoyment and personality matter more than you might think. In July a team from University College London published a study in July 2025 of 132 adults, comparing an eight‑week cycling and strength program with a resting control. They asked participants to rate how much they enjoyed each session and matched those ratings against personality traits. Extroverts preferred high‑intensity interval training while neurotic types liked short bursts and privacy.

Conscientious participants were fitter overall but not necessarily happier. Crucially, everyone who completed the program got stronger and fitter regardless of their trait. Dr Flaminia Ronca, the study’s lead author, said the key to sticking with exercise is as simple as doing something you enjoy. Her colleague Professor Paul Burgess put it bluntly: people high in neuroticism showed the biggest drop in stress because the training suited them. The researchers’ conclusion was clear: to improve activity levels, find an exercise you enjoy.

That idea isn’t new, but it’s now backed by data. A Washington Post piece this October summed up one small experiment where trainers split 41 adults into two groups. One group followed a typical, regimented program; the other focused on enjoyment and collaboration. After eight weeks, the “fun” group exercised longer and more often than the control group. The science is clear that people are far more likely to stick to a routine if they think it’s fun. It’s not rocket science: human beings repeat behaviours that make them feel good and drop ones that don’t.

As a bloke who grew up measuring everything, this hit me between the eyes. I can recount my personal bests down to the kilo and minute. But I’ve also burned out more than once because I treated training like a job. I forgot how kids exercise: they run, jump, climb and tumble because it feels good.

New research on preschoolers supports that idea; Spanish scientists recently found that three‑ to five‑year‑olds who jump, run and play more have better working memory and problem‑solving skills. Speed, agility and muscular strength were the strongest predictors of cognitive ability. We don’t need a university degree to know why: kids move because it’s fun, and that movement feeds their body and brain. Somewhere between adolescence and middle age, many of us lose that.

Playfulness prevents boredom and encourages people to engage in social activities, which makes them more likely to stick with exercise. In studies of hundreds of adults, those with higher playfulness scores were more active, walked more and sat less. That lines up with what behavioural scientists have been saying for years: affective responses – how a workout makes you feel – predict whether you’ll do it again. When trainers in an intervention explicitly promoted pleasure and fun, participants’ moods improved and they stuck with exercise. Active video games produced a small but significant boost in enjoyment compared to traditional programs. The effect wasn’t huge, and the evidence was of low certainty, but the message was consistent: people do more exercise when it feels like play.

Doctors are catching on. In a blog post for the Medical Care Blog, family physician Anthony Fleg quoted National Institute for Play founder Stuart Brown: “The opposite of play isn’t work, it’s depression”. Fleg argued that adults suffer from an “adult‑play deficit” that has become a public health issue. He told a story about the New Mexico Senior Olympics: he watched elders throw rings at soda bottles at a village fair, laughing harder than the kids. Their T‑shirts read, “You don’t stop playing because you grow old, you grow old because you stop playing”. That motto rings truer the older I get. Play isn’t a childish distraction; it’s the glue that keeps people moving, socially connected and mentally healthy. So by all means, measure your VO₂max and track your splits. Just don’t forget to play like a kid along the way.

What is VO₂ Max?

VO₂ max (maximal oxygen uptake) is the highest rate your body can take in, transport, and use oxygen during hard exercise. It reflects the combined efficiency of lungs, heart, blood, and working muscles.

• Unit: ml·kg⁻¹·min⁻¹ (oxygen per kg body mass per minute)
• Why it matters: higher values mean stronger aerobic capacity and better endurance.
• Key drivers: genetics, training status, age, sex, altitude, and sport mode (run vs bike).
• How it’s measured: lab treadmill/bike test with gas analysis; wearables provide estimates.
• Typical ranges: recreational 30–50; trained 50–60; elite endurance 70+.