We count the rings on a tree to find its age. Scientists have now found we can measure the age of people by getting them to stand on one leg. This shows how well a person can balance, and balance becomes more difficult as we get older. A researcher said balance was important because it requires input from vision, hearing and other senses. He said: "Good balance…leads to improved quality of life and healthy ageing."

Researchers tested the balance of people over the age of 50. Each person had to balance on their stronger and weaker leg for 30 seconds. They did this with their eyes both closed and open. People who stood on their weaker leg showed the highest rate of decline with age. The rate for the weaker leg was half a second higher per decade. The researchers said balance was a sign of health because "it reflects how the body's systems are working together".