Come rain or shine there is something about 9am on Saturday which draws hundreds of people to the promenade in Swansea. It's the same in dozens of other locations in Wales. You could run 5km any time of the week outside of work, and many people do, but still they come for a weekend dose of parkrun medicine. Some participants look fresh as a daisy, a few a little worse for wear. Some are old, some young, some heavyset, some whippet thin. Some really motor, some happily jog, others shuffle along. A few push buggies while a couple even run barefoot.

Like any busy running event the curious sight of bobbing heads in front of you indicates the Swansea Bay parkrun is again under way. You start beside The Secret Beach Bar and Kitchen then head along the prom to Blackpill where you turn and run back. And that's it.

What is the appeal of this weekly ritual? "It's very much the camaraderie," said accountant Julie Hartley-Green, aged 50, who takes part regularly with her daughter Sophie. "People are very friendly and welcoming. You can go at your own pace or be competitive if you want. And it's a regular, consistent thing." If ever evidence were needed that humans are social animals and creatures of habit parkruns are a case in point.

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Sophie Hartley-Green has clocked up nearly 200 parkruns. Clearly she like her mother has caught the bug. "It's a nice social event and I know lots of people here," said the 17-year-old. We are talking after a parkrun in late October – a still morning framed by the bay with the sun low on the horizon.

Francis Heron, a former production manager at a bakery in the north of England, is in the autumn of his running career but looks fit as a fiddle. The 71-year-old moved to Swansea two and a half years ago and started the parkrun shortly afterwards. He too said he liked the regularity and social aspects of the event and also the chance to test himself. "It's every Saturday come hell or high water," he said. "You run against yourself. You can see if you're getting better or worse."

For Zoe Perry, 50, of Bishopston, Gower, the parkrun is a family affair. "My husband and two kids do it," she said. "It's a chance to catch up with people, it's a nice release from work, and it starts your weekend off. The weather doesn't really matter." Bryant Gomez is relatively new to the event after being recommended by a friend to give it a go. "I do track 100m and you only suffer for a few seconds," said the 24-year-old of Birchgrove. "Here the suffering is more prolonged. The mental aspect of distance running is the hardest part. I'll definitely keep going though. I find it really fun and every time I do it I'm slightly less tired."

Another newcomer, Edwin Reji, was also given the heads-up by a friend. "This course is known as being one of the fastest," said the 20-year-old accounting and finance undergraduate. "It's all abilities and great fun. It gives me motivation and boosts my morale." The winner of the youngest runner of the day is undoubtedly five-year-old Harrison Meyrick, of Clydach, who normally does the 2km junior parkrun on Sunday but joined his father, Simon, for the longer version. "I was quite inspired," said Simon. "We ran together – it's a really nice course especially on a day like this. My parents also do it without fail."

Barefoot runner Hans Thompson cuts a lean figure belying his 70 years. He's spent a lot of time outdoors – kayaking around Britain as a teenager and delivering yachts in warmer climes in his 20s for example. "I've been running since I was about 50 – I only took it up to keep fit for other sports," he said. "Then it's sort of taken over." He began running without shoes three or four years ago. "I like to do it once a week to keep my feet and ankles strong," he said. "I think I'm faster. It forces you to land on your whole foot. It increases your cadence – at least it does with me – and keeps your 'form' good. It also makes you very aware of the surface you're running on."

Manisha Rickards, of Gower, used to do a parkrun near Cross Hands, Carmarthenshire, prior to the Swansea Bay one starting nine years ago. "It's very social," she said. "That's the reason people keep coming back." Like many participants she is also a member of a running club and has made good friends. The 61-year-old added: "Running has actually improved my arthritis."

The health benefits of running are well-established and organisers of Swansea Bay parkrun are keen to liaise with groups including 5K Your Way, an initiative of the charity Move Against Cancer. Area ambassador and consultant haematologist Rhian Fuge said the benefits of running for people affected by cancer can include increased immunity and improved recovery from chemotherapy and radiotherapy. "Some studies even show better survival," she said. Some participants run, she said, while others walk. "Plus we all get together afterwards, have a coffee, and share experiences," said Dr Fuge.

The parkrun concept was born in the UK 20 years ago at a jogging event in London. There are now said to be 10m registered runners in 23 countries. Wales has 57 parkruns, including three in prison grounds, and 24 junior parkruns. The aim is to expand from 81 to 100 by 2027. Chris Davies, national parkrun coordinator for Wales, said Sport Wales had funded new parkruns over the past year and that ongoing financial support came from insurance company Vitality, The Co-op, footwear company Brooks and fitness app WithU. Supporters can help by donating via parkrun Forever.

Swansea Bay parkrun has six run directors including two event directors – Karen Dusgate and Jeremy Brooks – and area ambassador Mark Faulkner. The directors take it in turns to organise the weekly event, allocating tasks to volunteers, dealing with any health and safety issues, and processing the results. "A lot happens in the run-up to a Saturday," said Mr Faulkner. He joked that his wife was to blame for his involvement after she took him to a parkrun in Newport, where they lived, 12 years ago. He was "shattered" after his first run, he said, but persevered. "I lost weight, got fitter, and joined a social running club," said the 65-year-old. That led to longer distance events and also parkrun volunteering stints.

"Parkrun is a door-opener," he said. "You just come down and enjoy yourself. You find people in the same position as you health-wise, mental health-wise." Mr Faulkner recalled there being 120 to 130 participants when the Swansea Bay parkrun initially got going. These days it's usually between 500 and 600 per week, hitting a record 714 on Easter Saturday 2024. Once a month volunteer pacer runners take part to help participants achieve personal bests should they wish to.

Mrs Dusgate, a runner herself, began volunteering after overhearing a participant express her sense of achievement following treatment for cancer. "She was just over the moon," said Mrs Dusgate. "It was quite emotional. It's amazing hearing stories and seeing what people have achieved – the confidence that has grown and the friendships formed." One man, she said, completed the 5km run on his 91st birthday.

Not everybody can run or even walk the parkrun. Helen Davies, of Pennard, Gower, has a condition which causes poor muscle control and she is pushed in her wheelchair. Prior to that she had completed 205 parkruns. "About eight years ago I had trouble with falling over so started walking them," said Mrs Davies. "I now know that I have progressive ataxia and cannot even stand as I have no balance and coordination. My friends from when I played golf come and push me as I still enjoy it. I don't usually go if it's going to rain so rely on the weather and my friends. My husband, Gordon, still takes part and has done over 300. I know I'll not catch him up." She added: "I feel I have achieved after a parkrun. There is a brilliant feeling of camaraderie there and they make everyone feel welcome."

Given the large number of joggers and the fact that the promenade is there for other users – dog walkers, cyclists, people on scooters – volunteer marshals like Gary Gregor perform an important role. The 77-year-old, of West Cross, used to run but now guides joggers round the loop. "I like seeing people I know," he said. "I appreciate my hometown of Swansea. It's lovely standing at Blackpill looking across the bay."

"Bad egg that one, mind!" joked fellow marshal Malcolm Phillips about Mr Gregor. Mr Phillips got involved through his granddaughter and travels from his home in Baglan to anchor himself at "Malcolm's corner", as he calls it, not that far from Mr Gregor. "I could go to the one at The Gnoll [in Neath] as it's nearer but I like it down Swansea Bay," said the 88-year-old. "I know quite a few of the runners by name."

Alan Griffiths, 78, is another regular volunteer. "I love it," he said. "It gets you up in the morning. I have a bit of banter with Malcolm and Gary." The former runner describes himself as "a bit of a poacher-turned-gamekeeper". A major health issue emerged out of nowhere a few years ago leaving him feeling "empty" and losing speed. "I could see my [finishing] times going down, down, down," said Mr Griffiths. "It was chest pain but I thought it could have been other things – diet for example."

The retired teacher, who lives with his wife in Mountain Ash but has an apartment in Swansea Marina, discovered he'd inherited a heart condition from his father. He had major surgery around two years ago and reckoned his years of running helped him recover quickly afterwards. "I'm fine now, absolutely fine," he said. "I can walk anywhere. I tried running but there was something that just said to me: 'You really shouldn't be doing this.' I have learned my lesson. When you run you think you are immortal but you are not."