WASHINGTON (AP) — First lady Michelle Obama is trying to help set a world record for the most people doing jumping jacks in a 24-hour period.An overcast sky and light drizzle didn't stop Mrs. Obama from leading about 400 elementary and middle-school students from Washington, Maryland and Virginia in one minute of continuous jumping jacks on the South Lawn.To break the record, more than 20,425 people from around the world must be recorded doing jumping jacks by 3 p.m. EDT Wednesday. National Geographic Kids magazine is supporting her initiative by hosting events across the country in schools, malls and other places.A proponent of healthy eating and exercise, Mrs. Obama says there are many ways for people to keep moving. Hundreds of kids sought her out for high-fives, hugs and handshakes.