Image copyright Getty Images Image caption The ancient art of Tai Chi combines deep breathing and relaxation with gentle movements

Adults are advised to do muscle-strengthening exercises twice a week, as well as aerobic exercise, to help them stay active for longer, under new guidance from the UK's top doctors.

For the first time, it includes advice on safe activity levels for pregnant women and new mums.

Dance, bowls or Tai Chi are advised for over-65s to reduce falls in old age.

Physical activity protects against obesity, type 2 diabetes, heart disease and depression, the advice says.

The new guidelines on physical activity have been produced by the UK's chief medical officers and updated to reflect the latest scientific evidence.

Their message is that any activity is better than none, and more is even better.

Prof Dame Sally Davies, England's chief medical officer, said most children and adults in the UK are not active enough.

"We need more active travel, we need people to get off the bus or the tube a stop early.

"We need people to climb stairs instead of getting in a lift...

"We need to be more active."

The guidelines recommend that adults build strength and balance to help stave off the natural decline in muscle mass and bone density that starts around the age of 50.

Image copyright Getty Images Image caption Babies should have 30 minutes of tummy time when awake every day

What is recommended in the guidelines?

For under-5s

infants - 30 mins of tummy time - when the baby is on its front - for infants not yet mobile every day

toddlers - 180 minutes per day doing active play

pre-schoolers - 180 minutes per day of physical activity, including at least 60 mins of moderate to vigorous exercise

For 5-18 year olds

at least one hour of moderate to vigorous physical activity per day across the week, such as PE, active travel, after-school activities and sport.

develop muscle fitness and bone strength

minimise time spent being sedentary

For 19-64 year olds

aim to be physically active every day

develop or maintain strength of muscles by doing heavy gardening, carrying heavy shopping or resistance exercise - 2 days a week

at least 150 minutes of activity, such as brisk walking or cycling, or 75 minutes of vigorous activity like running each week

minimise time spent being sedentary - break up long periods of inactivity

Image copyright Getty Images Image caption Heavy gardening is one way of strengthening adult muscles

For over-65s

some physical activity is better than none

on two days a week, activity to improve muscle strength, balance and flexibility, including Tai Chi, dance, bowls and aqua-aerobics

each week, 150 minutes of moderate-intensity aerobic activity, building up gradually

break up prolonged periods of being sedentary with light activity when possible, at least with standing

For pregnant women

aim for 150 minutes of moderate-intensity activity every week

vigorous activity is not recommended for women who were previously inactive

don't bump the bump

do muscle strengthening activities twice a week

For after childbirth

aim to build up to 150 minutes of activity every week

build up to muscle strengthening twice a week

start daily pelvic floor exercises as soon as you can

For disabled adults

physical activity is not a risk and brings similar benefits to the rest of the adult population

Tim Hollingsworth, from Sport England, said it was great to see the strength and balance exercises on a similar footing to cardiovascular exercise.

"The beauty of it is there are many ways to build strength and balance, whether it's at home, at the gym or through sport.

"Resistance training, circuit training, racquet sports and yoga are all great, for example, for improving muscle function, bone health and balance."

Dr Max Davie, from the Royal College of Paediatrics and Child Health, said families must try to build exercise into daily routines by walking or cycling to school, for example.

"We know that by doing so, it can have major mental and physical health benefits for their growing child both now and in the future," he said.