Every cell needs energy to work.
Most of this usable energy is produced by mitochondria, small structures found inside cells. They turn nutrients from food into fuel that cells can use.
Mitochondria are especially important in organs and tissues that need a great deal of energy, including the heart, brain and muscles.
As we age, mitochondria may become less efficient. They may produce less energy and create more waste products that place stress on the cell.
Scientists call this mitochondrial dysfunction.
The term means that the cell’s energy-producing system is no longer working as effectively as it once did.
This change usually happens gradually. It may affect some tissues more than others.
A small decline may have little effect in one part of the body, but it can matter more in the heart, brain or muscles, where the need for energy is high.
Reduced mitochondrial function may contribute to tiredness and lower physical performance. But fatigue alone does not prove that mitochondria are not working properly.
Tiredness has many possible causes, including poor sleep, anaemia, thyroid disease, infection, medication, depression and heart conditions.
Mitochondrial dysfunction is therefore a biological process, not a diagnosis that should be made from one symptom.
Mitochondria also do more than make energy.
They send signals that influence metabolism, inflammation and repair. When they are under stress, they can affect how the whole cell responds.
This is one reason mitochondrial health is connected with several other parts of ageing, including DNA damage, problems with glucose control and the build-up of damaged cells.
Physical activity is one of the best-established ways to support the body’s energy systems.
During exercise, muscles need more energy. With regular training and enough recovery, the body adapts by becoming better at producing and using that energy.
This does not mean that more exercise is always better. Activity should match a person’s health, fitness and ability to recover.
Adequate sleep, balanced nutrition, not smoking and good control of blood pressure, cholesterol and glucose also support the conditions in which mitochondria work.
Many products claim to “boost mitochondria”, but a supplement cannot replace movement, sleep and good metabolic health.
There is no single routine test that can describe mitochondrial health across the whole body.
The most meaningful signs are practical: maintaining strength, endurance, organ function and the ability to recover from physical effort.
