Hidden risks of On sneakers: The trendy shoe is loved by loved by It-girls, dads and finance bros… but experts now issue an alarming warning about their design

They are the instantly recognizable sneakers that, according to the company behind them, are so comfortable they feel ‘like walking on clouds’.

But the unusual technology behind On’s distinctive hole-filled soles began with something less celestial – pieces of garden hose glued to the bottom of a running shoe.

The unlikely experiment was the brainchild of retired Swiss triathlete Olivier Bernhard who was looking for a sneaker that would provide both a cushioned landing – and a powerful ‘take off.’

Launched in 2010, On initially targeted serious runners, but its sneakers are now just as likely to be seen on the feet of celebrities and parents on the school run. They cost, on average, between $140-$200 and according to recent estimates, 400 million pairs were sold in 2025 in the United States alone.

Model Emily Ratajkowski and pop star Jennifer Lopez have been seen sporting a pair, while Dune actress Zendaya features in their adverts.

Yet foot health experts, speaking to the Daily Mail, have warned that the unusual soles may have a downside – increasing the risk of painful foot problems under some circumstances. 

Meanwhile, research suggests ‘maximalist’ sneakers with highly cushioned soles – including Hokas and some On models – may provide little or no extra protection from running injuries, and could even increase the impact on the feet and legs. 

So what is the truth about one of the world’s trendiest sneakers, and could wearing them for the wrong activities be doing your feet more harm than good?

According to Los Angeles-based foot and ankle surgeon Dr Bob Baravarian, while Ons may be fine for everyday wear, ‘walking on clouds’ might not be such a good idea for more strenuous exercise. 

‘I think these shoes are average overall, they’re more of a gimmick than actually a good shoe,’ he tells the Daily Mail. 

‘The waffle design on the base of the shoe doesn’t do anything amazing, and the soles have a lot of flexibility. The originals were far too bendy.

‘So, I think these shoes are fine if you’re on a short walk or taking them to the office. But if you’re planning a long run or a hike, I wouldn’t recommend these.’

So, what is it about Ons that might make them less than ideal? 

Baravarian is quick to point to the flexibility of some On models, warning that a shoe which can easily be twisted or bent in half may not provide enough support for some people’s feet. 

‘In general, we’ve been taught that soft and mushy soles is what we want. But what you may really need is something that is more solid and supportive,’ says Baravarian. 

‘A shoe is like a brace – it should support your foot and keep it stable. Many people have flatter feet with lower arches, so they may need more support.

‘Without it, the muscles and tendons in the foot have to work harder, which can lead to pain and other problems.’

These, he said, include plantar fasciitis. 

The condition, which affects the thick band of tissue that runs along the bottom of the foot and supports the arch, is the most common cause of heel pain in the US, affecting around one in 10 Americans at some point in their lives.

It can cause a dull, constant ache or a sharp, stabbing pain when putting pressure on the foot.

The condition is thought to result from repeated strain on the plantar fascia. Other factors that may heighten the risk include long periods of time on your feet, running, sudden increases in exercise and wearing shoes that do not adequately support the foot. 

Too much strain on the feet can also cause tendonitis, where a tendon becomes irritated or inflamed. 

One of the most common forms is Achilles tendonitis, affecting the tendon that connects the calf muscles to the heel bone. It is particularly associated with repeatedly overloading the tendon, such as suddenly increasing the distance or intensity of running.

And while it might seem logical that an ultra-cushioned shoe would protect the feet and legs from these stresses, research suggests this isn’t necessarily the case.

In one study, researchers found runners wearing highly cushioned ‘maximalist’ sneakers actually experienced greater impact forces than those wearing conventional running shoes.

Researchers suggested this was because runners instinctively stiffened their legs when landing in the softer shoes, effectively cancelling out some of the benefit of the extra cushioning.

Experts also raised concerns about whether the lattice structure of the sole always compresses evenly as someone walks.

Dr Bruce Pinker, a podiatric surgeon based in New York City, explained that during a typical heel-to-toe walking gait, the shoe should compress progressively as weight moves from the heel towards the front of the foot.

However, he warned that the hollow pods in On shoes may sometimes compress unevenly, potentially causing the foot to roll inwards and increasing the risk of pain or injury.

‘That may be particularly the case with older Ons that have become worn from regular use,’ he adds.

‘If the base compresses unevenly, that can raise the risk of instability which may cause a biomechanical injury such as an ankle sprain.’

The open holes and spaces in the shoes’ soles could also pose another, more unusual problem.

Stones, twigs and other debris can become wedged in the gaps – which experts say could potentially interfere with the way the sole compresses.

It is a surprisingly common complaint among On owners online.

One recent Reddit post showing rocks and even a stick lodged in a pair attracted more than 23,000 upvotes, with the owner complaining that they regularly had to stop and pull debris from the soles.

And then there’s the squeaking.

Social media forums are littered with complaints from On owners who say their sneakers developed an irritating squeak – in some cases so loud they claim they stopped wearing them altogether.

The problem has even ended up in court.

In October last year, two customers from California and New York filed a proposed class action lawsuit against On, alleging that its CloudTec shoes produced a ‘loud’ and ’embarrassing’ squeak with every step.

The lawsuit claimed the noise was caused by parts of the distinctive rubber sole rubbing against one another as the wearer walked. On requested to have the case dismissed and, last month, the judge agreed, saying there was already evidence online that the shoes may squeak before the claimants bought the products. 

The experts we spoke to were particularly concerned about older versions of the On Cloud model – the shoe that helped propel On into the mainstream and pairs of which are likely still lurking in cupboards across America.

They noted that some of the brand’s newer shoes have stiffer, more supportive soles.

All also stressed that Ons remain hugely popular and that they rarely see patients with problems they attribute specifically to the shoes. There is also no substantial evidence that Ons, in particular, cause foot problems.

‘Really, the old Ons, the ones that made On popular, were not very good shoes,’ said Baravarian. ‘They were more of a design shoe. They were fine for walking and had the cool factor, but I don’t think they were good for serious exercise.

‘Overall, I think these shoes are generally fine for walking – going to the office or wearing them for short periods while you’re out and about. If you’re lifting weights, they’re fine too.

‘But for running and more intense athletic activity, I think there are far better shoes out there.’

The Daily Mail contacted On for comment.