Scientists Found the Switch That Explains Why Exercise Reverses Muscle Ageing

Trump declared the Iran ceasefire "over." Oil surged 5%. The Dow fell more than 500 points. Chips somehow recovered.

The quick scan: Wednesday was the sharpest geopolitical shock since early May. Trump declared the Memorandum of Understanding with Iran "over" after the US resumed strikes overnight, sending oil up more than 5% and Treasury yields higher. FOMC minutes released Wednesday showed some Fed members had discussed a rate hike in June, adding a second layer of pressure. The Dow fell sharply. The NASDAQ, oddly, ended positive – chip stocks rebounded on Broadcom's Apple deal extension and reports of Chinese H200 purchases.

S&P 500: -0.28%, 7,482.71 – rredit-sensitive and energy-import sectors led losses while tech provided partial offset
Dow Jones: -1.09%, 52,348.39 – American Express (-3.80%), Sherwin-Williams (-3.49%) and Boeing (-3.03%) led losses; 23 of 30 components declined
NASDAQ: +0.20%, 25,870.65 – Broadcom +4.8% after expanding its Apple partnership, Nvidia +3.6% on Chinese H200 demand reports. The index briefly turned negative late in the session on Trump's escalation comments before recovering.

What's driving it: Two simultaneous shocks. First, Trump saying the Iran ceasefire "is over" – adding that US forces would "probably hit them hard again tonight" – sent oil above $74 per barrel, raising inflation fears and pressuring rate-sensitive sectors. Second, FOMC minutes showed that some policymakers saw a case for a rate hike in June, reinforcing the view that the Fed is not done. JPMorgan fell 2.5%, Visa dropped 1.3%. Against this backdrop, the chip rebound was striking: Broadcom's expanded Apple deal confirmed ongoing AI supply chain momentum, while Nvidia's gain on Chinese H200 demand suggests AI spending continues despite geopolitical turbulence.

Bottom line: The Iran ceasefire, which markets had spent two months pricing in, has now officially been declared over by the US president. For L-Plate Retirees, this is the scenario the diversified, liquidity-buffered portfolio was built for. Oil above $74 means inflation expectations rise again. Rate hikes are back on the table. The divergence between chips (recovering) and everything oil-sensitive (falling) is the market telling you the AI trade is structurally separate from the geopolitical trade – even when they share headlines.

Your Muscles Have a Reset Button. Exercise Is How You Press It.

The scoop: We've known for decades that exercise helps maintain muscle strength in older adults. We've known it works. What we haven't fully understood – until now – is why. At the molecular level, what is actually happening inside ageing muscle cells when you work out, and why does the same exercise produce dramatically different results in different people?

A new study from Duke-NUS Medical School, published in the Proceedings of the National Academy of Sciences, has the most specific answer yet. And it comes from researchers right here in Singapore.

The problem inside ageing muscles

To understand the finding, it helps to understand what goes wrong in ageing muscles first.

Healthy muscles depend on a constant cycle of production and removal. The body builds new proteins and clears out damaged ones. A growth pathway called mTORC1 regulates this balance – controlling protein production, muscle maintenance, and repair. When mTORC1 works properly, the muscle stays strong, repairs effectively, and recovers from use.

The problem with ageing is that mTORC1 can become excessively active. When that happens, muscles prioritise building new proteins while becoming progressively less efficient at removing damaged ones. Damaged proteins accumulate inside muscle cells. The cells come under stress. Muscle strength gradually declines.

Until this study, scientists didn't fully understand what was driving mTORC1 out of balance in older muscles.

Introducing DEAF1

The researchers identified a gene called DEAF1 as the key driver of this imbalance.

DEAF1 levels rise in ageing muscles. As DEAF1 increases, it drives mTORC1 activity higher, disrupting the protein production-removal balance and accelerating muscle deterioration. Normally, DEAF1 is regulated by a group of proteins called FOXOs. But FOXO activity naturally declines with age. As FOXO weakens, DEAF1 is no longer kept under control – its levels rise, and the muscle moves progressively away from repair and maintenance.

The researchers confirmed this mechanism in both fruit flies and older mice. When they artificially raised DEAF1 levels, muscles weakened more rapidly. When they lowered DEAF1, the balance of protein production and removal improved and muscle strength was restored. The gene plays a consistent, conserved role in muscle ageing across different species.

How exercise resets the switch

The discovery that gives this study its particular significance is what exercise does to DEAF1.

"Exercise can reverse this process, correcting the imbalance," said Assistant Professor Tang Hong-Wen, the study's lead author. "Physical activity activates certain proteins which lower DEAF1 levels, bringing the growth pathway back into balance. This allows aging muscles to clear out damaged proteins, rebuild themselves properly, and help them stay stronger and more resilient."

In other words, when you exercise, you're not simply building new muscle fibres. You're triggering a molecular process that suppresses DEAF1, restores the protein-removal machinery, and essentially resets the muscle's ability to maintain and repair itself. Exercise tells the muscle to clean up and start again.

This is why the research team describes the finding as a biological "reset button." The mechanism was previously unknown. Knowing it exists, and knowing exercise activates it, gives scientists the most precise explanation yet for why physical activity is so effective at preserving muscle function into old age.

Why the benefit isn't equal for everyone

The study also explains something that anyone who trains with older adults will have observed: some people respond dramatically to exercise while others barely seem to benefit at all.

The research team found an important limitation. In some older muscles, DEAF1 levels become extremely high, or FOXO activity drops so significantly that the normal regulatory system becomes unresponsive. In those cases, exercise alone may not be enough to fully restore the muscle's repair capacity.

"This finding may help explain why some older adults experience greater benefits from exercise than others," the researchers note.

This is not an excuse to stop exercising. It is useful information about why starting earlier – before DEAF1 levels have accumulated and FOXO has weakened substantially – produces better results than starting later. The earlier you establish consistent exercise habits, the more responsive the DEAF1-FOXO system remains. Each decade of consistent exercise is an investment in the responsiveness of the very mechanism this research has identified.

The Singapore angle

This research has particular resonance for Singapore readers, for two reasons.

The study comes from Duke-NUS Medical School in Singapore, conducted with collaborators from Singapore General Hospital and Cardiff University. Duke-NUS is already one of the leading centres for ageing research in Asia, combining basic science with translational research aimed specifically at improving outcomes for Singapore's rapidly ageing population.

The second reason is the policy context. Singapore's ageing demographics make muscle preservation not just a personal health issue but a public health one. The researchers note explicitly that muscle loss increases demands on caregivers and healthcare systems as populations age. Findings like this one contribute directly to Singapore's ongoing investment in understanding and addressing the health challenges of an older society.

What comes next from this research

Beyond the exercise insight, the researchers note that DEAF1 also influences muscle stem cells – the cells responsible for helping muscles repair and regenerate tissue. These stem cells naturally become less effective with age, and disruptions in DEAF1 make recovery even harder.

The implication is that targeting DEAF1 could eventually reproduce some of the beneficial effects of exercise at the molecular level – helping maintain muscle strength even when physical activity is limited, such as after surgery, during illness, or in people managing chronic conditions like cancer. That therapeutic application is further away. The exercise application is available now.

"Lowering DEAF1 helps older muscles regain strength and balance, almost like hitting the rewind button," said Priscillia Choy Sze Mun, the study's first author. "With millions of older adults at risk of muscle decline, understanding DEAF1 could lead to new ways to protect muscles and improve quality of life."

Actionable Takeaways for L-Plate Retirees

• This research confirms that exercise is doing something specific, not just generally beneficial. DEAF1 suppression is the molecular mechanism. Knowing this exists changes the framing from "exercise is good for you" to "exercise is the only currently available way to activate the molecular reset that keeps ageing muscles functioning." That's a more compelling reason to maintain consistency.

• Start earlier rather than later. The study found that in muscles where DEAF1 levels have become very high or FOXO activity has declined significantly, exercise may not fully restore the repair capacity. The mechanism remains more responsive the earlier it's engaged consistently. Consistent exercise in your 50s maintains the DEAF1-FOXO system in a state where it can still respond.

• Consistency matters more than intensity for this mechanism. DEAF1 suppression is triggered by physical activity – not necessarily maximal intensity activity. Regular movement that engages the muscles is what activates the pathway. The 90–120 minutes per week of resistance training supported by earlier fitness research aligns with this finding.

• Recovery from illness or surgery is a particularly high-stakes period for DEAF1. The study notes that muscle stem cell function – which DEAF1 also influences – becomes less effective with age. Getting back to exercise as soon as medically appropriate after a health interruption is not just about general recovery – it's about maintaining the muscle's molecular repair capacity.

• This is Singapore research, solving a Singapore-relevant problem. Duke-NUS's focus on ageing outcomes for Singapore's population means this research is specifically calibrated to the demographics and health challenges of this region. It's not a finding from a different population being extrapolated. It's directly applicable.

Your Turn:
The finding that exercise resets a specific molecular mechanism – not just that it's "good for muscles" – is a level of specificity most people haven't encountered before. Does knowing the mechanism change your motivation to stay consistent with exercise?
The study found that some older adults respond much less to exercise because DEAF1 levels have accumulated too high. Does that finding make you think differently about the urgency of establishing exercise habits now, rather than waiting?
Duke-NUS conducted this research specifically with Singapore's ageing population in mind. Does knowing that this finding comes from local research make it feel more relevant to your own situation?

👉 Hit reply and share your story – your insights could inspire fellow readers in future issues.

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