Walking slowly in later life may seem an inevitable part of getting older – but it doesn’t have to be.

A study has found that it is not caused by your brain, weight or nervous system. Instead, researchers say it is simply a loss of muscle strength which makes it harder to move.

And the good news is that simply exercising regularly could fix the problem, helping older people improve walking speed and ability.

A decline in walking can lead to a less active lifestyle, and is directly linked to a lower ten-year survival rate for people at age 75.

To see what could be driving the deterioration in walking speeds in pensioners, US researchers at Carnegie Mellon University in Pennsylvania examined the changes in elderly people’s skeletal, muscular and nervous systems.

The scientists used computer simulations to predict how these changes affect gait. The model they used consisted of a musculoskeletal system, based on the human body, and a neural controller, like the brain, which was used to drive the simulated muscles.

They found that only ageing in muscle properties resulted in a decline in walking.

These changes cause muscle fatigue, which means people in their seventies tend to cover 60 centimetres (0.6 yards) of ground less per second than people in their twenties.

Pensioners use up 16 per cent more energy than youngsters when walking, which makes it far harder because they tire more quickly.

The study, published in the Journal of Physiology, points out that difficulty in walking is reversible, but concludes that building up muscles in the legs may be the only effective answer.

The authors wrote: ‘The results suggest that reversing these changes is the only effective way to enhance the performance of elderly walking. Physical training has been shown to achieve such a reversion, although it remains unclear precisely which training regimes work well.’