What's Good For You - Season 1 Episode 4

What’s the best toothbrush to use—automatic or manual? Michael Slater puts both to the test. Do we really have to exercise for 20 minutes in order to burn fat? Leila McKinnon works up a sweat to find out. We’ve all heard laughter is the best medicine, but can it help prevent heart attacks? Will eating spinach really give us the strength of Popeye? How long can we hold our breaths for? Dr Andrew Rochford pushes the limits on a Californian free dive.