This Overlooked Muscle Change Could Be Driving Age-Related Decline
Your body is built to handle stress—not the chronic, grinding kind, but the short, sharp kind that comes from a hard workout, a cold morning run, or a steep hill climb. That kind of stress is what your muscles need to stay resilient as you age.
A new preprint from researchers at Monash University (which means it has not yet been peer reviewed), suggests that the ability to respond to this kind of stress (not just avoid it) may be one of the most important factors in how well we age.
About the study
Researchers investigated the role of an enzyme called NOX4, which produces small amounts of reactive oxygen species (ROS) in skeletal muscle. While excessive ROS can damage cells, low levels act as important signaling molecules that help activate NFE2L2 (also known as NRF2), a protein that regulates antioxidant defenses and cellular repair.
The team examined muscle tissue from both mice and humans and also studied what happened when NOX4 was removed from skeletal muscle in aging mice.
When this muscle signal fades, the body starts to struggle
The researchers found that NOX4 levels naturally decline with age in both mice and humans. As NOX4 decreased, activation of NRF2 also dropped, leading to greater oxidative damage and poorer muscle function.
Mice lacking NOX4 experienced an accelerated decline in health as they aged, including more severe muscle loss, frailty, increased body fat, inflammation, insulin resistance, and signs of liver disease.
Notably, many of these changes improved when researchers activated NRF2 using sulforaphane, a compound found in cruciferous vegetables.
How to keep your stress-response system strong as you age
While this research was largely conducted in mice, it highlights the importance of maintaining the body's ability to adapt to stress. One of the most effective ways to do that is through regular exercise.
Exercise temporarily increases ROS production, which may sound counterintuitive, but those short bursts of stress help activate protective pathways like NRF2. The findings also add to growing interest in foods rich in sulforaphane—such as broccoli sprouts, broccoli, Brussels sprouts, and kale, which may help support these cellular defense systems.
The takeaway
Aging well may be less about eliminating stress and more about preserving the body's capacity to adapt to it. According to this new study, the NOX4/NRF2 pathway in skeletal muscle may be central to that adaptive system, and its decline with age appears to be driven largely by declining physical activity rather than aging itself.