At the start of lockdown earlier this year, unmoored from normality, I found myself drawn to a decade-old book called You Are Your Own Gym by Mr Joshua Clark and Mr Mark Lauren, a former fitness trainer for US Special Operatives. Doing pull-ups on the top of a door spoke to me of resourcefulness and resilience – although, as prescribed, I used a towel to protect my hands. I drew comfort from making some small progress in stasis, seeing some sort of the future mapped out amid the uncertainty in the tables of workout programmes.

Exercise has been a crutch for me since long before I started writing about health and fitness. I almost always feel better mentally when I exercise and worse when I don’t, which I’m aware isn’t necessarily healthy. And I’ve been acutely aware of my own mental health since a friend and former colleague took his own life a little over two years ago. Almost as shocking was the number of people I knew personally and professionally who, in the wake of his death, revealed that they, too, had suffered mental health problems; to the extent that they’d needed therapy, medication or both. Whenever things have felt precarious, then and subsequently, I’ve leaned into my crutch.

Science supports me on that. “Around the world, people who are physically active are happier and more satisfied with their lives,” Dr Kelly McGonigal, a research psychologist and lecturer at Stanford University (and, incongruously, a group fitness instructor), writes in her book The Joy Of Movement, which came out last December. “This is true whether their preferred activity is walking, running, swimming, dancing, biking, playing sports, lifting weights or practicing yoga.” And, presumably, doing pull-ups on the top of a door.

During physical activity, Dr McGonigal goes on to explain, your muscles secrete hormones, nicknamed “hope molecules”, that make your brain more resilient to stress. In one study, subjects were injected with a drug that induces panic attacks. Exercising for 30 minutes before was shown to significantly counteract the effects. So, you should be able to handle anything 2021 throws at you, then.

Physical activity reduces inflammation in your brain, protecting against anxiety and depression in the long run, rewires it to be more receptive to joy and releases a potent cocktail of feel-good chemicals including pain-relieving, mood-boosting endocannabinoids (which cannabis mimics). These “don’t worry, be happy” molecules cause the so-called “runner’s high”. But any moderately difficult, heart-raising activity that you perform for 20 minutes can trigger it, writes Dr McGonigal. The resulting buzz is therefore more accurately termed a “persistence high”.

One evolutionary theory suggests that two million years ago climate change forced early humans in east Africa to travel farther for food. We adapted with longer leg bones, large, powerful gluteals and stiff, propulsive feet to make our upright stance even more efficient. But we also needed motivation: hence the persistence high. Regular exercise “resembles a habit-forming drug” in many respects, writes Dr McGonigal, but takes longer to get hooked on and, unlike narcotics, increases rather than annihilates your capacity for pleasure: “Looking at the evidence, it’s hard not to conclude that our entire physiology was engineered to reward us for moving.” 

But the trade off is that if we don’t move, our physiology actively penalises us – physically and mentally. Studies cited by Dr McGonigal show that 88 per cent of subjects who reduce their daily step count become more depressed; after a week, their life satisfaction drops by 31 per cent. I experienced this first-hand after a few days’ staycation in September during which I misguidedly gave myself a break from exercise. I effectively took away my crutch. And on a larger scale, restrictions on movement and locked-down gyms risk exacerbating the pandemic’s mental health toll. A study published in June showed an average decrease in daily step count of 27.3 per cent.

As part of its “Barry’s Cares” initiative, the fitness studio Barry’s offered support to its clients during isolation from its mental health first-aider employees, plus one-to-one calls with other members of staff for those who just wanted to talk. “Our community needed us,” says Barry’s UK co-founder and master trainer Mr Sandy Macaskill. “When we reopened, people were telling us that our workouts saved their lives during a really difficult period.”

Physical activity also changes your brain in a similar way to falling in love or having a child, priming you to bond and cooperate – another evolutionary advantage. “Endorphins are especially effective at strengthening ties to individuals we are not related to,” writes Dr McGonigal. Moving together makes external threats less intimidating and imbues “we agency”, a sense of empowerment through joint action that studies show is experienced by participants in marches and demonstrations. Moving in time, or synchrony sparks “collective joy”: the feeling of being part of something bigger than yourself. Research has found that fitness tribes function like religious groups, providing meaning and comfortingly predictable rituals, forming communities and looking out for each other.

“A few years ago, it really hit me how often I was hearing clients say they were coming to us to feel better [mentally],” says Mr Macaskill. Even before the pandemic, Barry’s was training staff to spot mental health red flags in clients or colleagues and refer them to professionals such as Ms Zoë Aston, a psychotherapist and mental health consultant who has collaborated with other gyms and activewear brand lululemon. 

“Exercise, used well, is excellent for mental health,” says Ms Aston, with that crucial caveat. “We have to be doing it out of love for our bodies and not attempting to punish them for the way they are, particularly at times like the present.” Red flags that exercise has itself become an issue include major inconsistencies in energy levels, training on an injury because you feel you can’t stop or using exercise as escapism on a regular basis.

“Exercise is a double-edged sword,” concurs personal trainer Mr Ollie McCarthy. When he was a student, his then-girlfriend tried to take her own life. He used exercise as a distraction, making himself too tired to think. Years later, he ran the Brighton Marathon for suicide prevention charity Campaign Against Living Miserably (CALM), for which he’s now a running coach.

Mr McCarthy, like Dr McGonigal and Ms Aston, makes the distinction between exercise and movement, which “takes away the pressure” that the former can bring. There’s a time and place for structured, results-oriented exercise, but that isn’t always here and now. Whereas movement is something we need daily and often – at least four times a day during lockdown, says Ms Aston, whether that’s walking around the block or unpacking the dishwasher: “If we don’t move around, not only do our bodies ache, but our minds do, too.”

Balance is different for everybody, says Ms Aston, who recommends experimenting with different forms of physical activity, finding something that feels challenging, not difficult, and giving yourself permission to step back from anything that negatively affects you. Self-care can mean going for a run, or it can mean not because you recognise that you’d be doing it for the wrong reasons, or that you’d benefit more from a foam roll and a bubble bath. This year has made it difficult to stay tuned into what our bodies and minds really need: “Move if you can and love yourself even when you cannot.”

Mr McCarthy now enjoys a healthier relationship with exercise. He focuses more on rest and recovery (sleep has had the biggest impact), doesn’t beat himself up if he misses a scheduled training session and listens to his body, moderating his activity level accordingly and often running without a phone or watch. “The real benefits of exercise I’ve found aren’t distraction,” he says, “They’re connection with yourself.” 

Sadly, the physical activity and camaraderie of our weekly five-a-side game wasn’t enough to keep my friend with us. And it would be facile to suggest that exercise can completely inoculate you against anxiety in a pandemic, or that a depression sufferer simply needs to be more physically active when they can’t even get out of bed. Everything will not magically be awesome if you just work out. And however strenuously we try to fortify ourselves against life’s tribulations, mental health issues can strike any of us, at any time. But a moving target is at least harder to hit.