Get on the treadmill

Interval training lowers cholesterol, decreases the risk for blood clots, and can even reverse heart disease. "Interval training is the most effective way to increase the pumping capacity of your heart because the rest periods make it possible to work at a higher intensity," says Paul Robbins, a metabolic specialist with Athletes' Performance in Arizona. Perform this 42 minute routine twice a week. If your heart rate is not dropping 20-plus beats between intervals, then take more rest and skip an interval. You'll need a heart rate monitor, oh, and a towel. This might get sweaty.

Warm up

Jog for five minutes at a pace at which you can easily hold a conversation.

Minute 1

Sprint at 90 to 95% of your maximum heart rate (MHR). To calculate your MHR, multiply your age by 0.55 and subtract from 202.

Minute 2

Run at 75 to 80% of your MHR.

Minute 3

Sprint at 90 to 95% of your MHR.

Minute 4

Run at 75 to 80% of your MHR.

Minute 5

Sprint at 90 to 95% of your MHR.

Recovery

Walk or jog for three minutes.

Repeat

Repeat the five-minute intervals and active recovery four times.

Warm down

Jog for five minutes at conversation pace.