According to an article from the February 2012 issue of Good Housekeeping magazine, you should think of a tough workout as the gift that keeps on giving. When researchers from Appalachian State University in Boone, NC, asked cyclists to bike at a vigorous pace for 45 minutes. They found that post-ride, the exercisers burned an extra 190 calories - 37% of what they'd burned while cycling. And the metabolism boost lasted up to 14 hours. While the study was conducted on men, the authors expect that women will see similar benefits. To maximize your calories burn and blast fat, they advise that you work u a sweat for 45 minutes three times a week (a spinning class or other intense cardio is great.).