During hibernation, brown bears spend up to six months lying almost completely still, without eating, drinking or exercising. When spring arrives, they leave their dens with their muscles largely intact.

For humans, the same period of inactivity would usually mean severe muscle loss, weakness and long-term health problems. Even a few weeks in bed after surgery can reduce strength and mobility. For older adults, hospital patients and people with chronic illness, long-term immobility can permanently change quality of life. How do bears manage what humans cannot?

To explore this question, my colleagues and I studied how bears protect their muscles during hibernation. Our findings, published in Acta Physiologica, suggest that the answer lies deep inside their muscle cells, in the way they manage energy over long periods of inactivity.

Muscle cells rely on structures called mitochondria to supply the energy needed for movement and basic function. These structures convert nutrients into fuel, allowing muscles to contract, repair themselves and adapt to stress. In people who stop moving for long periods, mitochondria usually decline in both number and performance. Energy production drops. Muscles weaken. Recovery becomes harder.

Bears take a different approach. During hibernation, their muscles contain fewer mitochondria, but the........

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