Don't even say you don't have time to squeeze in a workout this holiday season.
High-intensity interval training hit a new low recently with a study that found that even extremely short bursts of intense exercise just a few times a week produced real fitness improvements.
Test subjects pedaled as hard as they could for 20 seconds on exercise bikes, then rested for two minutes, before repeating two more times for total of one minute of intense pedaling per session. After doing this three times a week for six weeks, endurance levels jumped an average of 12 percent.
Most also saw lower blood pressure and increases in mitochondrial activity, which is involved in energy production at the cellular level. Men in the study also had better blood sugar levels.
"Short-term interval training, using a protocol that involved only 1 min of very intense exercise within a total time commitment of 10 min ... was a potent stimulus to induce physiological adaptations that are linked to improved health," reads the study, published recently in the online peer-reviewed scientific journal PLOS One.
But just how low can you go when it comes to exercise times?
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This is probably about it, says lead researcher Professor Martin Gibala, an exercise physiologist with McMaster University in Ontario, Canada.
"I think we are reaching the limits," Gibala tells Military Times. "Ten-second repeats could work if you did a sufficient number of repeats. There are even studies that have used 6-seconds-on, 12-seconds-off approaches, but a relatively large number of repeated cycles were performed."
Gibala has been at the forefront of modern HIIT research.
This summer he was among the featured speakers on the topic at an Army-hosted gathering of top military health and fitness leaders during the 3rd International Congress on Soldiers' Physical Performance in Boston. In 2006, his team found that 3-minute intervals of intense pedaling on a stationary bike, followed by a quick rest — repeated about a half-dozen times — was the equivalent of up to two hours of less intense pedaling when it came to building muscle. In a follow-up study, Gibala found that quick HIIT workouts burned 900 percent more fat than typical aerobic exercise.
This most recent study shows that "short, repeated bursts of very intense exercise was a time-efficient strategy to improve markers of health and fitness," Gibala says.
While the research focused on 14 overweight, but otherwise healthy, subjects, Gibala says he believes the findings are applicable to most people.
"Interval training is not a panacea for everything. Our study is in no way meant to suggest this is the best way to train, or that a few brief bursts of intense exercise will provide all the benefits of traditional exercise training as reflected in the public heath guidelines. That being said, intervals can be an effective means to induce health and fitness benefits with reduced exercise time commitment."
For those new to HIIT, he recommends easing into it.
"If you want to try intervals, start slow and just get out of your comfort zone to start. Our study used a relatively extreme all-out model, but this is not the only method of interval training. Generally speaking, though, there appears to be an intensity-duration trade off."
