What's wrong with sprint interval training?
You might have seen news reports about a recent study showing
that less than 10 minutes of intense exercise a week could be "as
effective as an hour of daily moderate activity."
"Short bouts of very intense exercise improved muscle health and
performance comparable to several weeks of traditional endurance
training," says study co-author Martin Gibala, an associate professor
in the department of kinesiology of McMaster.
Here in England, the research was featured on breakfast
TV, and I got a lot of questions from people wanting to know "if
it was really true."
Let's take a closer look at what happened
in the study to see what it all means for you. The research, published in the Journal of Applied Physiology, shows that just 15 minutes
of sprint interval training over a two-week period was enough to
improve exercise performance by almost 100% [2].
The study was conducted on 16 subjects, all of whom were "recreationally
active." In other words, they took part in some form of exercise
2-3 times per week, but none was engaged in a structured training
program.
Eight of the subjects (6 men and 2 women) performed the
two-week interval training program. The other participants
did no exercise. The program consisted of between four
and seven 30-second bursts of "all out" cycling followed by four
minutes of recovery three times a week (Monday, Wednesday, and Friday)
for two weeks.
Subjects were encouraged to pedal as fast as possible during the
30-second sprint. During the four minute recovery period, they
remained on the bike and either rested or cycled at a low speed.
Exercise performance was assessed before and after the training
program by measuring how long the participants could cycle at an
intensity equivalent to 80% of their VO2peak before giving up.
The result?
After training, the individual improvements in performance ranged
from 81% to 169%, with the exception of one subject (a 16% decrease)
who had injured his ankle before taking the final exercise test.
However, even when his results were included, the average time
to fatigue in
the sprint interval group increased from 26
to 51 minutes, despite no change in VO2peak. The control group showed
only a very small improvement.
The muscles of
the trained group also showed a significant increase in citrate
synthase, an enzyme that is indicative of the tissue's ability
to use oxygen.
"The findings really are exciting," says
Edward F. Coyle, PhD, director of the human performance laboratory
at the University of Texas, Austin. "In
today's society, people spend so much time in front of the TV or
video screen. It is rare we exercise either intensely or for very
long times. Since some people are devoting so little time to exercise,
this reminds us how effective or efficient even short amounts of
exercise are if performed very intensely."
So, can you get results with such a small amount of exercise?
Well, it depends what you mean by "results."
Remember, the researchers were measuring changes in exercise
performance. They weren't interested in weight loss.
Although high-intensity interval training is popular with some
people who want to lose fat, it does have some limitations.
No matter how hard you push yourself,
there are only so many calories you can burn in such a short period.
It's true that an intense workout boosts oxygen consumption (called
excess post-exercise consumption, or EPOC
for short) and
calorie expenditure after exercise to a greater extent than moderate-intensity
activity.
However, EPOC is linked with both exercise intensity
(how hard you work) and exercise duration (how long you work for)
[1]. In my experience, "waves" of intervals interspersed with steady-state
cardiovascular exercise works better for fat loss than interval
training alone.
In fact, this was the approach I used to get in shape for a recent
photo shoot (you can see some of the
pictures here). Although the workouts take a little longer
(30-40 minutes) than a "pure" bout of interval training
(which you can often get done in 20 minutes or less), I was still
able to get in and out of the gym — shower
included — in less than one hour.
It's also worth pointing out that sprint interval training is very hard
work.
"The exercise, although only 30 seconds for each of the
four bouts, is as hard as you can go," Coyle says. "So the first 15 seconds
feel not so bad, and the last 15 seconds are hell."
That's one reason I prefer using shorter
intervals lasting around 15 seconds, especially when my goal is
losing fat. I think you get many of the same benefits with
a lot less pain.
About the Author
 Christian Finn holds a master's degree in exercise science, is a certified personal trainer and has been featured on BBC TV and radio, as well as in Men's Health, Men's Fitness, Muscle & Fitness, Fit Pro, Zest and other popular fitness magazines.
If you want better, faster results from the time you spend in the gym, click here now for instant access to his step-by-step muscle-building and fat-burning workout routines.
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References
1. Borsheim, E., & Bahr, R. (2003). Effect of exercise intensity,
duration and mode on post-exercise oxygen consumption.
Sports
Medicine, 33, 1037-1060
2.
Burgomaster,
K.A., Hughes, S.C., Heigenhauser, G.J., Bradwell, S.N., & Gibala,
M.J. (2005). Six sessions of sprint interval training increases muscle oxidative
potential and cycle endurance capacity in humans. Journal
of Applied Physiology, 98, 1985-1990
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