Physical activity ideas for parents and babies

Physical activity ideas for parents and babies, am looking for ways to stay in shape & play with my newborn. Any ideas?

When my older son was a baby, we used to take him for walks around the block in a stroller. I know it's not much exercise for the baby, but it was a great workout for me, since at the time the house we lived in was on a hill, and the walk was difficult pushing the stroller all that way.

Other things you might try, when the baby can crawl:
* crawl races - eg, go slow to compete with the baby & see who 'wins'
* tickles - yes, they get some exercise that way & you'll laugh too.

Best,

thedude