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Thu August 7, 2014
Interval Training While Walking Helps Control Blood Sugar
Originally published on Thu August 28, 2014 6:43 pm
Lots of high-performance athletes use interval training to maximize their fitness.
From runners to cyclists to boot-camp fanatics the strategy involves alternating between periods of high-intensity and lower-intensity aerobic training.
And the type of exercise involved? Taking an hourlong walk each day outdoors or on a treadmill.
As part of the study, researchers enrolled about 30 volunteers with Type 2 diabetes who were in their late 50s and early 60s.
The volunteers were divided into groups. One group was instructed to walk three minutes briskly, followed by three minutes at a more restful pace, and repeat that process for an hour.
Another group walked at a continuous pace for the same amount of time.
A third group, a control group, kept up normal routines, which didn't include daily exercise.
"What we expected to see ... was that both exercising groups would have an improvement in their glucose [or blood sugar] control," says study author Thomas Solomon, an associate professor at the University of Copenhagen who studies how exercise affects glycemic control.
But that's not what happened.
The interval walkers did improve. Their glucose disposal — the ability to move sugar out of the circulating bloodstream and into parts of the body where it can be used as fuel — improved by 20 percent compared with the nonexercising group. And their hemoglobin A1C levels, a longer-term measure of blood sugar, dipped slightly too.
But the steady-paced walkers saw no improvement at all.
"This was somewhat surprising, considering that they were doing one hour of exercising a day for four months," says Solomon.
So what explains the benefits of interval walking? It's not exactly clear, but there's a leading theory.
"It's this switch between the intensities that we think is critical here," says Solomon. "You're able to work hard, and then rest hard ... rather than just walking at a fixed pace."
And during the high-intensity bursts, your muscles need more fuel in the form of glucose.
"It makes sense that intervals would help people with blood sugar control," says Dr. Tim Church, a professor of preventive medicine at the Pennington Biomedical Research Center in Baton Rouge, La.
He explains that our muscles are the No.1 consumer of blood sugar in our bodies.
So, when we do things such as short bursts of high-impact aerobic activity, "you're pulling excess sugar out of the blood, which results in healthier blood sugar levels," Church says.
This study is small, but the findings match other research on intervals, which find benefits that seem to go beyond better blood sugar.
In a study published in Diabetes Care in 2013, which also compared interval walkers with continuous-paced walkers, Solomon and his colleagues found that the interval walkers lost more weight and lowered their cholesterol levels.
"There are a number of studies that have shown that when you increase the intensity [of aerobic exercise] in the form of doing intervals, there's additional benefits beyond just the calories burned," Solomon says.
There are still unanswered questions, he adds, such as can interval walking cut the risk of strokes or other health problems that are associated with diabetes?
"We really need to understand how this has an impact on the long-term health of these patients with diabetes," Solomon says.
AUDIE CORNISH, BYLINE: Many high-performance athletes use interval training as a way to maximize their fitness, from runners to swimmers and cyclists. The strategy is to alternate between periods of high intensity and lower intensity training. NPR's Alison Aubrey reports on new research that finds this strategy can be useful for lots of us, even those who just want to get the most out of their time on a treadmill.
ALISON AUBREY, BYLINE: I often start my day on a bike right here - a stationary bike that's set up right here in my bedroom. My kids are getting ready for camp. It's kind of easy on this setting. The resistance is only at two. So the question is, should I dial it up?
TIM CHURCH: Yeah, absolutely. There is absolutely a benefit to interval training whether you're a weekend warrior, a high-performance athlete or just someone trying to get physically fit.
AUBREY: That's Tim Church. He directs exercise research at the Pennington Biomedical Research Center in Baton Rouge.
CHURCH: There are a number of studies which have shown that when you increase the intensity in the form of doing intervals, there is additional benefit beyond just the calories burned for that amount of exercise.
AUBREY: So this is what it looks like. I'm just going to dial it up from a resistance setting of two all the way up to about seven.
Compared to evenly paced exercise, the interval approach has been shown to be more effective in helping people lower cholesterol and lose weight. And now a new study published just this week finds that even when you're walking, alternating between a brisk pace and a leisurely pace - that can help control blood sugar. Thomas Solomon at the University of Copenhagen is the lead author. He conducted a four-month-long experiment. Middle-aged volunteers in their late 50s and early 60s, all of whom had type two diabetes, agreed to walk for an hour each day. Some were instructed to do interval walking - three minutes fast, three minutes slow. And another group was told to walk at a steady pace for the same amount of time. Their blood sugar control was assessed at the beginning and then at the end of the study.
THOMAS SOLOMON: What we expected to see originally, actually, was that both exercising groups would have an improvement.
AUBREY: But that's not what happened. Only the interval walkers lowered their blood sugar. The continuous walkers saw no benefit.
SOLOMON: This was, I suppose, somewhat surprising considering that they were doing one hour of exercise a day for four months.
AUBREY: But researcher Tim Church says he can understand why this may have happened. He explains that when we alternate the intensity of aerobic exercise to include these intense periods, we're working our muscles harder, and as a result, our muscles need more fuel in the form of glucose.
CHURCH: It's interesting. When you talk about diabetes, we often think about the pancreas, but the largest consumer of blood sugar in the human body is skeletal muscle. So when you do things that increase the skeletal muscle's ability to utilize more blood sugar, you're pulling excess sugar out of the blood which results in healthier blood sugar levels.
AUBREY: So I'm cycling a lot harder now. The bike is telling me my heart rate's at about 132.
And I'm feeling it. So even if you're not worried about blood sugar, this interval approach, to me, sure feels like a good workout. Alison Aubrey, NPR News. Transcript provided by NPR, Copyright NPR.