Work Up a Sweat in Less Time
No time for exercise? Pick up your pace, and you can work less and still get better results. University of Alberta researchers reported in September that a group of healthy people who wore pedometers and made an effort to take an extra 5,000 steps a day (about 50 minutes of walking) showed no improvement in their physical fitness after six months. But another group that hit the gym only four days a week for 40 minutes of moderately intense workouts (visualize walking as fast as you can without actually running) significantly increased their endurance levels.
In essence, the harder you work, the more efficiently you can increase your fitness. A study published in the September Journal of Physiology compared two groups of cyclers who engaged in six exercise sessions over two weeks and found that those who did 30-second sprints mixed with four-minute rest periods for 30 minutes had the same improvements as those who biked at a moderately intense pace for more than 90 minutes. "All-out sprints call every muscle cell into action, while traditional endurance workouts allow some cells to sit there dormant," explains study leader Martin Gibala of McMaster University in Hamilton, Canada.
Improved fitness means your muscles are able to better use oxygen, which translates into increased energy and better blood pressure and cholesterol levels. "With high-intensity workouts, you can get these benefits in three or four days a week instead of five to seven days for a lower-intensity workout," says University of Florida researcher Michael Perri.
If you're just starting an exercise program, spend the first month building up to a 30-minute, moderately paced workout (about 4 to 4.5 mph on a treadmill) before you start interval training, recommends Conrad Earnest of the human performance research center at the Cooper Institute. Try jogging or power walking for 20-second intervals and walking slowly for 30 to 60 seconds in between. But-as always-check with your doctor first.
This story appears in the December 25, 2006 print edition of U.S. News & World Report.