Movement Can Change How Cells Respond at Any Age

Research published in PNAS connects exercise’s effects on aging with physical changes inside muscle-cell mitochondria. These structures turn food into ATP, the usable energy that supports muscle movement and brain activity. Their function declines with age, contributing to tiredness, loss of muscle, and lower physical capacity. The findings draw on experiments in mice alongside a clinical trial involving people.

For 12 weeks, aged mice were given running wheels. Compared with inactive mice of the same age, they improved in grip strength, stamina, and broader physical performance. Researchers linked those gains to remodeling within skeletal-muscle mitochondria. In a separate 12-week program, frail older adults with an average age of 78 completed resistance, balance, and gait exercises. Their frailty decreased measurably, while muscle biopsies showed mitochondrial patterns matching those observed in the mice.

Exercise increased certain proteins related to stronger mitochondrial function, including Cox7a1, which belongs to the mitochondrial respiratory chain. Higher amounts of these proteins in participants’ muscles were associated with larger performance gains. Researchers also blocked mitochondrial remodeling genetically in another mouse experiment. Although those mice continued using their wheels, they did not gain the same functional benefits. This demonstrated that remodeling was necessary for the improvements, rather than simply occurring alongside them. Adults around their eighties, as well as those nearing that decade, still showed meaningful changes after 12 weeks, indicating that mitochondria remain responsive across age groups.