Interval training gains in popularity
Once the domain of elite athletes, high-intensity fitness
has gone mainstream.
January 15 2007
For years, Michelle Cuellar exercised five days a week. "But
you wouldn't have known it by looking at me," says the 33-year-old
mother of two. "I felt fit - but I was still fat."
matter what Cuellar did - run on the treadmill for 30 minutes at a
time or attend the occasional spinning class or boot camp, her weight
rose. By last summer, she carried 176 pounds on her 5-foot-6 frame.
Then, last fall, for the first time in her life, Cuellar started shrinking.
She tried on a pair of pants "that hadn't fit since 1998 - and
they fit!" she says. "In eight weeks, 5 inches came off
my butt, 2 inches off my stomach. The weight - 7, 9, 12 pounds - just
started falling off."
breakthrough? "I started doing intervals," says the Centennial,
- short bursts of speed mixed into a running, biking, swimming, elliptical,
rowing or other aerobic workout - are nothing new for organized sports,
where they've long been a tried-and-true method to build speed and
power. What's new is that high-intensity interval training is being
discovered by average people, who like the speed but love the side
effects even more: weight loss, muscle toning and reduced workout
training is hot right now and getting hotter," says Joseph Grassadonia,
publisher of Santa Cruz-based OnFitness magazine, which is targeted
at personal trainers. "It's always been there, but we are writing
more and more about it because it's simply the fastest way to get
says she trimmed 10 minutes from her workout time simply by replacing
her old steady-state 30-minute, 6-mph treadmill jog with "Sprint
8," a 20-minute aerobic session peppered with eight 30-second,
8-mph sprints so intense that they left her gasping for breath.
8, the centerpiece of the book "Ready Set Go! Synergy Fitness,"
by Phil Campbell, has a growing list of believers. Gary Green, 45,
a Web-based businessman from Tustin, says he halved his workout time
and cycled off 25 pounds since switching to the program in August.
Internet marketer Robert Burns of San Diego, 43, says he lost 25 pounds
since May doing three swimming or running Sprint 8 workouts a week.
"I feel younger and get faster and faster every day," he
warn, however, that interval training is not a walk in the park. "At
first, I could barely sprint at 5 mph," said 31-year-old Dan
Conner, a Sacramento fitness store manager who lost 50 of his 265
pounds and 9 inches off his 45-inch waist since last May. "I
was dying. I couldn't breathe. But now my sprints are up to 7 mph
- sometimes 8. They leave me gasping. I know that a lot of people
don't want to push like this."
key to improving one's level of fitness, trainers and sports scientists
say, is shocking yourself.
a certain period of plodding along, doing the same steady-state jogging
and cycling, you don't progress - your body gets used to what you're
doing," says Christopher Drozd, a Santa Monica strength and conditioning
coach. "You have to literally shock your body off the plateau.
If you push yourself to the limit [with intervals], you're going to
get a new limit."
phenomenon is known as the "stress adaptation response,"
says Leonard A. Kaminsky, director of the clinical exercise physiology
program at the Ball State University human performance lab and editor
of the exercise guidelines manual of the American College of Sports
human body adapts to the stresses placed on it," he says. "Challenge
it, and it improves. To effect change, you need to overload your system
beyond what it is accustomed to. When you go beyond your aerobic threshold
[the point at which you are unable to bring in enough oxygen to support
the exercise] - to where you perceive that you're getting winded -
you initiate a chain of positive events that work for everyone. Even
nursing-home populations can improve."
improve fitness by upgrading the oxygen-processing system with new
capillaries and stronger lungs and heart, adding more mitochondria
(tiny cellular motors) to muscles, and developing a higher tolerance
to the buildup of lactic acid, a waste product associated with going
anaerobic (into oxygen-debt). A 2005 study of competitive cyclists
at New Zealand's Waikato Institute of Technology even found that intervals
can speed up serious athletes in midseason form; eight to 12 sessions
gave test subjects power gains of 8.7% for 1 kilometer and 8.1% for
4 kilometers over a control group of non-interval trainers.
it is the unexpected weight loss, time savings and sense of "feeling
younger" that have average exercisers most excited.
latter may partially come from a temporary increase in the release
of human growth hormone, which radically declines with age. A 2002
University of North Carolina at Greensboro study published in Sports
Medicine found that all exercise, both aerobic and strength training,
stimulates the release of the hormone, and that greater exercise intensity
- as in interval training - stimulates greater release. Human growth
hormone is known for many positive effects, including development
of lean muscle mass.
time-saving effect was documented in a 2006 study published in the
Journal of Physiology. The test found equal increases in fitness between
six short bouts of interval training over two weeks (20-minute cycling
workouts, consisting of repetitive 30-second all-out efforts each
followed by four minutes of recovery) and six longer, moderate-paced
sessions (90 to 120 minutes a day) over two weeks.
weight loss, surprisingly, does not mostly come from the interval
training itself (intervals use fast-burning glycogen, not slow-burning
fat, as fuel), but from its long-known aftereffect: It ramps up the
in 1985, a study in the American Journal of Clinical Nutrition found
that high-intensity training ramps up metabolism for 24 hours afterward,
whereas low-intensity training does not. A 1991 study in the International
Journal of Obesity found that more exercise intensity, not more duration,
provoked increased post-exercise oxygen consumption. And a study published
in December in the Journal of Applied Physiology and conducted by
a team at Canada's University of Guelph found that just two weeks
of alternate-day interval training increased moderately active 22-year-old
women's fat-burning ability by 36%.
this may help explain why Michelle Cuellar gained weight with regular
exercise - until she added intervals.
that resting metabolism does decline as you get older, it is not uncommon
to see regular exercisers add a pound or 2 per year over time,"
says Kaminsky. "Either that, or Michelle was stopping at Starbucks
a couple times a week" - a charge she denies.
fast, how much?
type of intervals are best? All-out, lung-heaving efforts for 30 seconds
followed by low-intensity recovery for two or three minutes, à
la Sprint 8, or longer-lasting, less-intense efforts with shorter
recovery periods in between?
latter have plenty of success stories too.
Kolakowski, a 27-year-old golf company executive from Austin, Texas,
says he dropped from 290 to 230 pounds in eight months by using Momentum,
a three-day-a-week, 25-minute workout program that features three-minute
intervals followed by a minute of recovery.
by Broomfield, Colo.-based Breakthrough Health & Fitness, the
program requires the user to wear a heart-rate monitor to help gauge
perceived levels of exertion.
cool thing is that you only need to push hard for three minutes at
a time before you get to rest," says Kolakowski, who mixes some
cycling and swimming in with his running workouts. "Anyone can
push for three minutes."
John Lindahl of Boulder, Colo., 45, a corporate program manager who
says he lost 50 pounds and 9 inches off his waistline with Momentum:
"In corporate America, we need a more efficient workout because
we all have less time nowadays."
fact that super-intense Sprint 8 and moderately intense Momentum are
both effective is good news. "Ironically, you can't do the same
intervals all the time - you'll stagnate," says Drozd, the Santa
Monica trainer. "You need variation - for your body and your
mind. For best fitness, mix short intervals and long intervals. Whatever
you choose to do, do it hard."
New Zealand study showed cyclists' performance gains plateauing after
eight to 12 interval sessions. "To keep increasing your fitness
after six weeks of intervals," says OnFitness' Grassadonia, "be
creative: push it even harder or longer, add hills, stairs, cross-training.
I'm a 55-year-old big-wave surfer, but I can hang with 20-year-olds
because I do very intense 10 mph sprinting on the treadmill, all-out
sprints in the pool - constantly mixing it up."
hard, however, may be a problem for some. "I find Sprint 8 invigorating,"
says Green of Tustin. "But I don't know if it's for everybody.
It's a pretty hard workout - mentally and physically." Physically,
although interval training can often be safer than regular steady-state
aerobics because it cuts exercise time and minimizes the repetitive
motion that often leads to injury, it can also initially be risky
for joints, tendons and muscles used to less intensity.
ramp up slowly over two to three weeks," says Breakthrough founder
Jonathan Roche. "Guys, in particular, will go all-out and waste
themselves." Properly done, a high-intensity work interval should
be followed by a low-intensity rest interval that allows your heart
rate to recover, or come down to a level where you're breathing comfortably.
Generally, the more intense the work interval, the longer the rest
a psychological perspective, intervals are tricky.
more fun because we like to be challenged to do better, but they are
more gut-wrenching and grueling," says Ron Jones, an Atlanta-
and L.A.-based corporate wellness coach. "Although we know that
lukewarm goals don't work very well, too-hard ones can frighten you
Roche, he advises taking it easy at first with slower, shorter efforts.
"I've had people do five-second intervals," he says. "Then
slowly - slowly - build on that success. Remember that it takes three
weeks to psychologically form a new habit, and six months to change
a behavior. Even seeing the physical changes that come with interval
training may not be enough to let you stick with it. You have to feel
good about what you are doing."
now 20 pounds lighter than six months before, thinks she's gotten
to that point. "My husband has offered to buy me a whole new
wardrobe," she says. "But I told him to wait until I get
down to a size 6."