dr. elizabeth lattimore says the cases often appear in clusters and right now there's a big one in richmond. they are not sure why, but know there's a lot more research that needs to be done. >>> well, what if you could burn lots of body fat by doing just 20 seconds of exercise? there's an interval workout that claims to have those results. advocates say it's one of the most efficient methods of exercise. we checked it out and asked them what's your workout? >> come on, you can do anything for 20 seconds, right? >> tabata is a high-intensity workout. how we work the tabata workout is 20 seconds on, ten seconds off. >> five, four, three. >> the idea is you go really hard during your 20 seconds, then you chill out, relax during the ten, then go super hard again and get your heart rate super high. you do this eight times, then move on to the next exercise. >> three, two, recover. >> one benefit is when your heart rate gets so high, it never comes down, so you couldn't work at that high intensity for two minutes, but when you break it up into you work out at a different level. a lot of people h