From The Desk Of Clarence Bass
Reducing Sprint Intervals from 20 to 10 Seconds
Probing Minimum Effective Dose and Acceptable Response
The only training program that works is one that people are willing and able to do. With obesity rising and sedentary living being the norm in the US and other developing countries, the search for a workable program takes on more importance with each passing day. A new study by the Vollaard group in the UK, first reported online November 24, 2017, in the journal Applied Physiology Nutrition and Metabolism, is spearheading that search.
“As the prevalence of physical inactivity remains high worldwide, there is an urgent need to establish alternative exercise interventions that are 1) effective at improving VO2max, and 2) acceptable to populations that are currently unwilling or unable to adhere to recommended levels of moderate intensity continuous training (MICT),” Vollaard et al wrote.
The Gibala group at McMaster University in Canada introduced high intensity interval training (HIIT) to fitness trainers around the world. In a long series of studies over more than 10-years, they demonstrated the effectiveness of sprint interval training (SIT) with only three, 20-second all-out sprints. One minute of all-out effort improved fitness and health as much as 45 minutes of moderate exercise: http://www.cbass.com/neuromuscular.htm
Importantly, Gibala et al warned that this type of training requires a very high level of motivation and may not be suitable for untrained individuals. That’s where the Vollaard group enters the fray.
Fitness and health psychologist Richard Winett, PhD, tells us that the Vollaard group has been in the forefront of the search for the minimum effective stimulus for developing cardiorespiratory fitness (CRF). “What has been found in ‘reduced-exertion, high intensity interval training’ (REHIT) is that only two, all-out 20 second sprints are needed to meaningfully increase CRF,” Winett wrote in the February, 2018, issue of his Master Trainer newsletter. The entire protocol takes only 10-minutes, including warm-up and cooldown.
The new Vollaard study has two parts; the first measures effectiveness and the second perceived exertion and emotional response. In short, does the protocol improve fitness and how do the participants respond to it. Are they likely to keep doing it on their own?
Thirty-six untrained men and women, average age 22, were randomly divided into two groups. One group performed a standard REHIT protocol doing two 20 second sprints and the other group two 10 s sprints. VO2max was determined before and after 6 weeks of 3 weekly training sessions. Perceived exertion and emotional response was assessed ~5 minutes after the second sprint.
A few preliminary sessions were devoted to gradually working up to all-out sprints of 20 or 10s. Training was supervised and attendance was 97 percent.
The 10-second group increased CRF by only 4%, while those doing 20s saw a clinically meaningful 10%. The minimally effective line had been crossed. Twenty seconds made the grade, but 10s didn’t. Two times 20 seconds all-out remains the shortest effective SIT protocol. (Ten and 15 second sprints have been shown to be effective in other studies, but only when there are many sprints.)
That left the all-important physical and emotional response to be determined. Was 10s more acceptable to the participants than 20s? The answer is “NO.”
“Reducing sprint duration in the REHIT protocol from 20 seconds to 10 s [lessens] improvements in VO2max, and does not result in more positive [emotional] responses or lower perceived exertion,” Vollaard et al wrote. “We conclude that in protocols with very few sprints the sprint duration should be longer than 10s…Our findings further support the use of the original REHIT protocol consisting of 2 x 20 s sprints, and strengthens our contention that REHIT represents an efficacious, time-efficient, and acceptable alternative to classic SIT and moderate intensity continuous training (MICT) for improving health and reducing risk of future morbidity and premature mortality.”
The Big Picture
No time for exercise! That was the obstacle voiced most often. It has been cleared for most people serious about exercise. Gibala, Vollaard, and others have developed genuinely time-efficient interval protocols.
As noted, the Vollaard group had already shown that a total time commitment of ten minutes 3 times a week meaningfully increases cardiorespiratory fitness. While reducing the sprint duration from 20 to 10 seconds would do little to reduce training time, they thought it might reduce negative emotional responses or perceived exertion. “This is important, because a criticism of SIT protocols has been that all-out sprints are too strenuous for untrained individuals: it has been suggested that performing all-out sprints requires too much motivation (which many sedentary populations lack), and is likely to evoke negative affect which may lead to subsequent avoidance of further exercise,” the researchers explained.
Finding that not to be the case in the new study, Vollaard et al “propose that the original protocol involving 20-s sprints remains the protocol of choice.”
Their study being the first to provide data on emotional responses and frame of mind following REHIT, they offer several interesting observations regarding other forms of aerobic exercise.
First, they say that longer SIT protocols with more sprints have been found to be aversive. Something I have repeatedly suggested to be the case with the often used 4 by 4 minute protocols. They’re a turn off for many people, including me.
Equally interesting, they say that studies of MICT, the usual alternative to HIIT and SIT, have shown an inverse U-shaped emotional response. Emotional impact often becomes negative during exercise, but then rebounds quickly following exercise.
Being that their study observed changes in mood state about 5 minutes after the second sprint, they say that future studies should determine whether mood changes at any point during the 10-minute session. “Still, that REHIT may be associated with positive affective response immediately post-exercise is in direct contrast to classic SIT (4-6 x 30-s sprints) and at the very least suggests that any potential negative responses will be short-lived.”
Again, they conclude reducing SIT from 20 to 10 seconds reduces improvements in fitness, while failing to reduce perceived exertion or make the exercise more acceptable. Twenty second sprints remain the protocol of choice for reduced-exertion, high intensity interval training.
Professor Winett ends his discussion of the new Vollaard study with this down-to-earth public health observation:
For many deconditioned adults, the sprints can consist of walking quickly up stairs in buildings with likely only two such ‘sprints’ needed, three times a week. This seems doable by many people and it appears time that public health caught up to this compelling evidence base and developed strategies to promote this kind of exercise.
Winett is not alone in this common sense observation.
Carol and I
often do intervals in the foothills above our home. We've found a hill
that we can "walk" up one side
The Stair Climbing Option
Once again, McMaster University Professor Martin Gibala is leading the way—out of the gym and onto the stairs.
“Stair climbing is a form of exercise anyone can do in their home, after work or during the lunch hour,” Gibala explained as lead author of a study summarized in Science Daily. “This research takes interval training out of the lab and makes it accessible to everyone.”
Gibala and his team found that brief, intense stair climbing is a practical way to boost fitness.
They recruited sedentary but otherwise healthy women to test the effect of two different protocols requiring a 10-minute time commitment, three times a week.
The first protocol involved three 20-second all-out bouts of stair climbing, and the second 60 seconds of continuous climbing up and down one flight of stairs. The second protocol could be easily done in the home.
Both protocols significantly increased cardiorespiratory fitness.
“Interval training offers a convenient way to fit exercise into your life, rather than having to structure your life around exercise,” Gibala wrote in his book The One Minute Workout.
For more details on the Gibala stair climbing study: https://www.sciencedaily.com/releases/2017/02/170207105329.htm
For an in depth discussion of the how and why of stair climbing for fitness and health, go to the British website “Step Jockey.” https://www.stepjockey.com/health-benefits-of-stair-climbing
Finally, a study dated February 14, 2018, found that climbing stairs lowered blood pressure and strengthened leg muscles in postmenopausal women: https://www.sciencedaily.com/releases/2018/02/180214093842.htm
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“What could be simpler than finding a set of stairs and climbing your way to health?” That’s the message from a friend who has been climbing the stairs in his high-rise apartment complex for years. He provided us with this up-to-the-minute info on stair climbing for fitness and health.
March 1, 2018
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