A newly identified muscle protein may help explain why people who stay active as they age often remain stronger and healthier for longer, according to new research. Scientists found that a protein called NOX4 naturally declines with age and inactivity. As levels dropped, researchers observed signs of frailty, muscle loss, insulin resistance, and liver disease in mice.

Exercise and NOX4

Researchers believe NOX4 helps muscles repair themselves and adapt to the physical demands of exercise. When NOX4 was removed from the muscles of mice, the animals became weaker, lost muscle mass, and developed health problems commonly associated with aging. The researchers also found that exercise helped restore NOX4 levels in older mice.

Josephine Hunt, an educational leader and former group fitness instructor, told Fox News Digital that the findings help explain why exercise benefits so many aspects of health. "Movement is medicine," Hunt said. "The emerging NOX4 research is exciting because it helps explain something exercise scientists have observed for decades. Physical activity does far more than strengthen muscles."

Hunt said many people view exercise as a way to improve appearance or fitness, but its effects reach much deeper. "Exercise appears to activate biological signaling pathways that help the body adapt, repair, and become more resilient over time," she said. Hunt added that healthy aging is about more than simply living longer. "Healthy aging is not just about adding years to life," she said. "It is about preserving strength, function, independence, cognitive health, and overall quality of life."

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