Published: Jun 2, 2013 | Updated: Jun 3, 2013

By Salynn Boyles , Contributing Writer, MedPage Today

Action Points

• A single, short bout of high-intensity exercise three times a week led to significant health benefits in slightly overweight men.
• Note that participants also saw changes in oxygen cost during running at a submaximal workload, blood pressure, and fasting glucose.

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A single, short bout of high-intensity exercise three times a week led to significant health benefits in slightly overweight men, researchers reported.

In the 10-week CONSORT trial, healthy but inactive men with a body mass index of 25-30 kg/m2 who followed two different training protocols saw increases of 10% and 13% in maximal oxygen uptake (VO2max) for a group difference ofP=0.08, wrote Arnt Erik Tjonna, from the K.G. Jebsen Center for Exercise in Medicine at Department of Circulation and Medical Imaging in Trondheim, Norway, and colleagues.

Participants also saw changes in oxygen cost during running at a submaximal workload, blood pressure, and fasting glucose, they wrote in PLOS One.

The authors explained that VO2max is a strong predictor of physical fitness and mortality. “Regular exercise training improves maximal VO2max but the optimal intensity and volume necessary to obtain maximal benefit remains to be defined,” they said, adding that there’s growing evidence that exercise training with low-volume but high-intensity may still offer health benefits.

“We have a worldwide obesity epidemic and even though people are told they should exercise around 30 minutes a day at least five times a week, only about 15% to 30% of people do this,” Tjonna toldMedPage Today. “Our study suggests that around 15 minutes of exercise, three times a week may have significant benefits as long as just a few minutes include intensive endurance training.”

For this trial, the men (ages 35-45) were recruited between January and April 2009. They had not done regular exercise for at least 2 years prior to the study. Exclusion criteria included unstable angina, recent cardiac infarction, severe valvular illness, pulmonary disease, uncontrolled hypertension, and orthopedic or neurological limitations.

The exercise consisted of walking, jogging, or running on an inclined treadmill. The two protocols consisted of the following:

• 4-AIT: 4 by 4 minutes of 90% of maximal heart rate (HRmax) interspersed with 3 minutes of active recovery at 70% HRmax
• 1-AIT: 1 by 4 minutes at 90% HRmax

Both groups did a 10 minute warm-up at an intensity that elicited 70% of HRmaxand a 5-minute cool down. Total exercise time per was 19 minutes in the 1-AIT group and 40 minutes in the 4-AIT groups.

The participants wore heart monitors while exercising, but Tjonna said in the real-world setting, it wouldn’t be difficult for exercisers to tell if they are working at 90% HRmax.

“At this level, your breathing should be heavy and you should not be able to talk in complete sentences,” he said.

In addition to similar improvements in VO2max, both groups saw a reduction in submaximal workload (14% after 1-AIT and 13% after 4-AIT).

Systolic blood pressure decreased by 7.1 mmHg in the 1-AIT group and by 2.6 mmHg in the 4-AIT group. Diastolic pressure decreased by 7.7 and 6.1 mmHg, respectively (P=0.84 group difference).

Both groups had a similar decrease in fasting glucose of about 5%.

However, only those in the 4-AIT group saw reductions in body fat (P=0.98), total cholesterol (P=0.71), low-density lipoprotein (LDL) cholesterol (P=0.96), and oxidized LDL cholesterol (P=0.07).

The authors cautioned that “the present investigation was a small, proof-of-principle study” and was likely underpowered to detect clinically meaningful differences between the groups. They called for “longer-term systematic replication studies with diverse participants…to more fully assess impacts on risk factors and at the molecular level.”

These participants should include older, sicker people and regular exercisers, Tjonna told MedPage Today.