Two minutes of hopping a day can strengthen hip bones in older people and reduce the risk of fracture after a fall, scientists have suggested.
A study led by Loughborough University showed bone density in the hopping leg improved after one year.
Bones thin naturally with age, and localised thinning in the hip is associated with an increased risk of hip fracture.
Researchers said their findings have major implications for the prevention and management of osteoporosis.
Increases of up to 7 per cent were identified in the bone mass of some parts of the outer shell (cortex) and in the density of the layer of spongy bone underneath this. They said that, importantly, there were improvements in the thinnest areas of the bone most at risk of fracture after a fall.
In the Hip Hop study 34 men aged between 65 and 80 perform a programme of hopping exercises on a randomly assigned exercise leg only. They were told to avoid any other changes to their physical activity or dietary habits during the year-long trial.
CT scans were then analysed to detect any changes in their bone density and showed clear visual differences between the exercise and control legs.
Dr Sarah Allison, who conducted the research at Loughborough University's National Centre for Sport and Exercise Medicine (NCSEM), said: "Hip fractures are a major public health concern among older adults, incurring both high economic and social costs. Those affected suffer pain, loss of mobility and independence, and increased risk of death.
"We know exercise can improve bone strength and so we wanted to test a form of exercise that is both easy and quick for people to achieve in their homes."
Dr Winston Rennie, a consultant radiologist who supervised the CT scans, said: "The bone maps show clear changes in bone, with localised adaptions at regions that may be important to reducing hip fracture."
Researchers said it was important to build up any exercise gradually, and hop with caution as falling could cause a fracture of weak bones.
The study was funded by a Medical Research Council interdisciplinary bridging award, and the bone mapping analysis by the National Osteoporosis Society.