Some days -- we've all been there -- the schedule is just too tight for a long stretch of exercise. So instead, you do a little bit here, a little bit there, and hope it all adds up. And yet you feel like you're cheating yourself.
New research in the journal Medicine and Science in Sports and Exercise may reassure you. Three 10-minute workouts offer more benefit in reducing risk of one measure of heart disease than does a continuous 30-minute bout of the same exercise, according to an article in the journal's August issue. The study, by researchers at the University of Missouri-Columbia, found that intermittent exercise lowers levels of triglyceride, a type of heart-unhealthy fat in the blood, more effectively than continuous exercise.
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Researchers measured triglyceride levels in 18 men and seven women, all healthy and aged 18 to 45. Each ran once on a treadmill for 30 minutes and, a week or so later, did three separate 10-minute sessions on the treadmill. Both times, their blood was drawn after several hours of rest. Each person ate a high-fat meal 12 hours after exercising; researchers took blood samples at two-hour intervals after the meal.
Triglyceride levels dropped an average of 27 percent after the intermittent exercise compared with 15 percent after the continuous workout. "The longer fat hangs around, the more dangerous it is," said study co-author Tom Thomas, professor of nutritional sciences at Missouri-Columbia. Triglycerides promote atherosclerosis (artery clogging) by boosting levels of "bad" cholesterol (LDL) and reducing levels of the "good" variety (HDL).
Each of the three 10-minute bouts of exercise was followed by a 20-minute rest period. All exercisers worked out with heart rates at 60 percent of maximum.
"We think something is occurring during recovery to explain this," Thomas said. It's his theory that a raised metabolic rate triggers a drop in triglyceride levels. That would explain the advantage of the shorter sessions: The intermittent routine included 60 minutes of recovery -- 20 minutes after each 10-minute session -- while the 30-minute routine gave the body only one 20-minute recovery, he said.
Thomas, who co-authored the study with Thomas Altena, an assistant professor of health and physical education at Southwest Missouri State University, cautioned against over-interpreting the results: Triglyceride level "is just one of hundreds of markers" of heart disease. People who have the time and dedication for continuous workouts should continue to do them, he advised. "This [study] tells us that intermittent exercise is also okay. It takes away one more excuse for not exercising."
Prior research has shown that the peak clearance of fat from the arteries occurs 12 hours after exercise and that the effect from one workout lasts for about 24 hours. "So if you eat at 7 p.m. and work out at 9 p.m., you are not clearing fat from that meal," Thomas said. "But you are good for the next 12 to 24 hours, and that's why daily exercise is important" -- because it almost ensures that your body is continually clearing fat from the arteries.
"Americans have a very-high-fat diet. The good news here is that exercise is a magic bullet [in fighting heart disease]. It seems to work for everyone."
No chat this week, but we're back in the cyber saddle next Thursday at 11 a.m. Until then, you can reach us at firstname.lastname@example.org. And keep moving -- however you can fit it in.
-- John Briley