Every time a cell inside your body replicates, a slither of your youth crumbles to dust. This occurs via the shortening of telomeres, structures that 'cap' the tips of our chromosomes.

Now, scientists in Israel say they've been able to reverse this process and extend the length of telomeres in a small study involving 26 patients.

The participants sat in a hyperbaric oxygen chamber for five 90 minutes sessions per week over three months, and as a result, some of their cell's telomeres were extended by up to 20 percent.

It's an impressive claim - and something many other researchers have attempted in the past without success. But of course it's worth flagging that this is a small sample size, and the results will need to be replicated before we can get too excited.

However, the fact that hyperbaric oxygen therapy appears to affect telomere length is a compelling link worth investigating further.

Lead researcher Shair Efrati, a physician from the Faculty of Medicine and Sagol School of Neuroscience at Tel Aviv University, explained to ScienceAlert how the inspiration behind their experiment was somewhat out of this world.

"After the twin experiment done by NASA, where one of the twins was sent out to the outer space and the other stayed on Earth, demonstrated a significant difference in their telomere length we have realised that changes in the outside environment may affect the core cellular changes that happens along ageing," said Efrati.

Telomeres are repeating chunks of code that act as the DNA equivalent of the plastic or metal aglet capping the end of a shoelace.

They copy themselves along with the rest of the chromosomes whenever a cell divides. Yet with every replication, tiny fragments of code from the very tip of the sequence fail to make it into the new copy, leaving the freshly minted chromosome a touch shorter than its predecessor.

As anybody who has lost the cap of their shoelace knows, it doesn't take long for the shoelace to lose its integrity. Similarly, shorter telomeres put sequences further down the chromosome at higher risk of hazardous mutations.

These mutations coincide with changes that predispose us to a bunch of age-related conditions, not least of all diseases such as cancer.

That's not necessarily to say that we age because our telomeres shrink, but there is a connection between telomere length and health that researchers are keen to investigate further.

"Longer telomeres correlates with better cellular performance," Efriti explained.

There are plenty of ways to accelerate the erosion of our telomeres. Failing to get adequate sleep could do it, as might chowing down on too much processed food, and maybe even having kids.

Slowing down the loss takes a bit more effort, but engaging in regular exercise and eating well are sound bets if you want your chromosomes to remain as long as possible.

A real achievement would be to flip our chromosomal hourglass completely and return lost sections of telomere. The fact that high-turnover tissues lining our gut do this naturally using an enzyme called telomerase has fuelled research over the years.

There have been plenty of milestones in attempts to achieve this task. Gene therapy in mice has shown it could one day be feasible in humans. More recently, stem cells from a supercentenarian woman had their telomeres completely reset outside of her body.

Some studies have found potential for tiny increases of maybe a few percent with provision of nutritional supplements such as vitamin D.

But while there are plenty of hyped promises of reversing aging in living humans already on the market, the reality of science-backed therapies we can use to give us the telomeres of a 20-year-old has been underwhelming.

Which is why the latest study is attracting so much attention. Far from a measly two or three percent, this latest study found telomeres in white blood cells taken from 26 subjects had regained around a fifth of their lost length.

The key, it seems, is hyperbaric oxygen therapy (HBOT) – the absorbing of pure oxygen while sitting in a pressurised chamber for extensive periods; in this case, five 90 minute sessions per week over three months.

HBOT has attracted controversy in the past for claims it could treat a range of conditions. It's usually the kind of therapy you'd give a diver who came up too fast from the ocean depths, or to kill off oxygen-sensitive microbes in a wound that just won't heal any other way.

But oxygen-rich environments are also behind a weird paradox, one where the body desperately stirs up a host of genetic and molecular changes that typically occur in a low oxygen one.

In this study, the researchers were able to show that the genetic changes provoked by the HBOT has extended telomeres, and also had a potentially positive effect on the health of the tissues themselves.

A slightly smaller sample of volunteers also showed a significant decrease in the number of senescent T cells, tissues that form a vital part of our immune system's targeted response against invaders.

Whether you'd sit in a small tank every day for a quarter of a year is a matter of preference, but future research could help make the whole process a touch more efficient, at least for some.

"Once we have demonstrated the reverse ageing effect on the study cohort using predefined HBOT protocol, further studies are needed in order to optimise the specific protocol per individual," Efrati told ScienceAlert.

In a press release from The Sagol Center for Hyperbaric Medicine and Research, Efrati says understanding telomere shortening is "considered the 'Holy Grail' of the biology of aging".

As significant as telomere shrinking seems to be, the failure of our biology as we age is no doubt a complicated matter involving far more than lost pieces of chromosomes.

Reactivation of telomerase is also a trick used by cancers to remain ahead of the growth-curve, making this holy grail a potentially poisoned chalice we need to understand better before drinking too heavily from.

Excitingly, research like this will help us develop a better picture of the aging process.

This research was published in Aging.