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FORGET THE
FAT-BURN ZONE
High Intensity Aerobics
Amazingly Effective
"Fat burn is
greater when exercise intensity is high." Izumi
Tabata
I believe in high-intensity
aerobics. In Ripped 3, for
bodybuilders, I recommended "a variety of relatively
short and infrequent aerobic sessions interspersed with
explosive muscular effort." In Lean For Life,
published six years later, I emphasized high-intensity
aerobics even more; I reduced the frequency
of aerobic sessions to two times a week (in Ripped
3 I recommended up to four) and substantially
increased the intensity. But it wasn't until recently, when my
friend Richard Winett, Ph.D., publisher of Master
Trainer, called my attention to new research
findings, that I came to fully appreciate the superiority of
high intensity aerobics compared to the usual prescription
that heart rate be maintained between 60% and 80% of maximum.
As explained in the nearby FAQ
(Low intensity aerobics?), high intensity aerobics burns the
same amount of fat as low intensity, but the expenditure of
calories is substantially greater; plus,
intense aerobics produces a higher level of fitness.
Importantly, the more fit you become, the more likely you are
to use fat as fuel for any given activity. And now, research
in Japan and in Canada shows that short, very intense aerobic
sessions are amazingly effective for both fitness and fat
loss.
Maximal oxygen uptake, or
V02max, is generally regarded as the best single measure of
aerobic fitness. As the rate of exercise increases, your body
eventually reaches a limit for oxygen consumption. This limit
is the peak of your aerobic capacity, or your V02max. As
intensity increases beyond V02max, your body must shift to
anaerobic (without oxygen) energy production. An oxygen debt
begins to build at this point and blood lactate levels climb.
In general terms, one's ability to continue exercising in the
face of rising oxygen deficit and lactate levels is called
anaerobic capacity.
This is important because
many high-intensity sports (including basketball, football,
soccer and speed skating) require a high level of both aerobic
and anaerobic fitness. Clearly, total fitness involves both
high V02max and high anaerobic capacity. A training protocol
that develops both would be a godsend.
Izumi Tabata and his
colleagues at the National Institute of Fitness and Sports in
Tokyo, Japan, compared the effects of moderate-intensity
endurance and high-intensity intermittent training on V02max
and anaerobic capacity. (Medicine and Science in
Sports and Exercise (1996) 28, 1327-1330).
Interestingly, the high-intensity protocol had been used by
major members of the Japanese Speed Skating team for several
years; it's a real-world training plan. As
you will see, however, the protocol is unique among aerobic
training programs for its intensity and brevity.
Many studies have been done
on the effect of training on V02max, but little information
has been available about the effect on anaerobic capacity.
That's because until recently methods for measuring anaerobic
capacity have been inadequate. This study used accumulated
oxygen deficit to measure anaerobic energy release, and is one
of the first to measure the effect of training on both aerobic
and anaerobic capacity.
Notice that the duration of
the moderate-intensity and the high-intensity protocols are
drastically different: (excluding warm-ups) one
hour compared to only about 4 minutes
per training schedule
Tabata's moderate-intensity
protocol will sound familiar; it's the same
steady-state aerobic training done by many (perhaps most)
fitness enthusiasts.
Here are the details (stay
with me on this): In the moderate-intensity
group, seven active young male physical education majors
exercised on stationary bicycles 5 days per week for 6 weeks
at 70% of V02max, 60 minutes each session. V02max was measured
before and after the training and every week during the 6 week
period. As each subject's V02max improved, exercise intensity
was increased to keep them pedaling at 70% of their actual
V02max. Maximal accumulated oxygen deficit was also measured,
before, at 4 weeks and after the training.
A second group followed a
high-intensity interval program. Seven students, also young
and physically active, exercised five days per week using a
training program similar to the Japanese speed skaters. After
a 10-minute warm-up, the subjects did seven to eight sets of
20 seconds at 170% of V02max, with a 10 second rest between
each bout. Pedaling speed was 90-rpm and sets were terminated
when rpms dropped below 85. When subjects could complete more
than 9 sets, exercise intensity was increased by 11 watts. The
training protocol was altered one day per week. On that day,
the students exercised for 30 minutes at 70% of V02max before
doing 4 sets of 20 second intervals at 170% of V02max. This
latter session was not continued to exhaustion. Again, V02max
and anaerobic capacity was determined before, during and after
the training.
In some respects the results
were no surprise, but in others they may be ground
breaking. The moderate-intensity endurance training
program produced a significant increase in V02max (about 10%),
but had no effect on anaerobic capacity. The high-intensity
intermittent protocol improved V02max by about 14%;
anaerobic capacity increased by a whopping 28%.
Dr. Tabata and his colleagues
believe this is the first study to demonstrate an increase in
both aerobic and anaerobic power. What's more, in an e-mail
response to Dick Winett, Dr. Tabata said, "The fact is
that the rate of increase in V02max [14% for the
high-intensity protocol - in only 6 weeks] is one of the
highest ever reported in exercise science." (Note, the
students participating in this study were members of varsity
table tennis, baseball, basketball, soccer and swimming teams
and already had relatively high aerobic capacities.)
The results, of course,
confirm the well-known fact that the results of training are
specific. The intensity in the first protocol (70% of V02max)
did not stress anaerobic components (lactate production and
oxygen debt) and, therefore, it was predictable that anaerobic
capacity would be unchanged. On the other hand, the subjects
in the high-intensity group exercised to exhaustion ,and peak
blood lactate levels indicated that anaerobic metabolism was
being taxed to the max. So, it was probably also no big
surprise that anaerobic capacity increased quite
significantly.
What probably was a surprise,
however, is that a 4 minute training program of very-hard 20
second repeats, in the words of the researchers, "may be
optimal with respect to improving both the aerobic and the
anaerobic energy release systems." That's something to
write home about!
What
About Fat Loss?
Angelo Tremblay, Ph.D., and
his colleagues at the Physical Activities Sciences Laboratory,
Laval University, Quebec, Canada, challenged the common belief
among health professionals that low-intensity, long-duration
exercise is the best program for fat loss. They compared the
impact of moderate-intensity aerobic exercise and
high-intensity aerobics on fat loss. (Metabolism
(1994) Volume 43, pp.814-818)
The Canadian scientists
divided 27 inactive, healthy, non-obese adults (13 men, 14
women, 18 to 32 years old) into two groups. They subjected one
group to a 20-week endurance training (ET) program of
uninterrupted cycling 4 or 5 times a week for 30 to 45 minutes;
the intensity level began at 60% of heart rate reserve and
progressed to 85%. (For a 30-year-old, this would mean
starting at a heart rate of about 136 and progressing to
roughly 170 bpm, which is more intense than usually prescribed
for weight or fat loss.)
The other group did a 15-week
program including mainly high-intensity-interval training (HIIT).
Much like the ET group, they began with 30-minute sessions of
continuous exercise at 70% of maximum heart rate reserve
(remember, they were not accustomed to exercise), but soon
progressed to 10 to 15 bouts of short (15 seconds progressing
to 30 seconds) or 4 to 5 long (60 seconds progressing to 90
seconds) intervals separated by recovery periods allowing
heart rate to return to 120-130 beats per minute. The
intensity of the short intervals was initially fixed at 60% of
the maximal work output in 10 seconds, and that of the long
bouts corresponded to 70% of the individual maximum work
output in 90 seconds. Intensity on both was increased 5% every
three weeks.
As you might expect, the
total energy cost of the ET program was substantially greater
than the HIIT program. The researchers calculated that the ET
group burned more than twice as many calories while exercising
than the HIIT program. But (surprise, surprise) skinfold
measurements showed that the HIIT group lost more subcutaneous
fat. "Moreover," reported the researchers,
"when the difference in the total energy cost of the
program was taken into account..., the subcutaneous fat loss
was ninefold greater in the HIIT program than
in the ET program." In short, the HIIT group got 9 times
more fat-loss benefit for every calorie burned exercising.
How can that be?
Dr. Tremblay's group took
muscle biopsies and measured muscle enzyme activity to
determine why high-intensity exercise produced so much more
fat loss. I'll spare you the details (they are technical and
hard to decipher), but this is their bottom line:
"[Metabolic adaptations resulting from HIIT] may lead to
a better lipid utilization in the postexercise state and thus
contribute to a greater energy and lipid deficit." In
other words, compared to moderate-intensity endurance
exercise, high- intensity intermittent exercise causes more
calories and fat to be burned following the workout.
Citing animal studies, they also said it may be that appetite
is suppressed more following intense intervals. (Neither group
was placed on a diet.)
The next time someone pipes
up about the fat-burn zone, ask them if they are familiar with
the Tabata and Tremblay research reports.
[You'll find high-intensity
aerobic workouts for bodybuilding in Ripped 3
and for balanced fitness, strength and endurance, in Lean
For Life; both books are in the
products section of this site. Routines specifically applying
Tabata-type intervals are explained in chapter 5 of Challenge
Yourself. Keep in mind that VO2max can only be
measured in the laboratory; you'll have to estimate 170% of
VO2 max. Don't try to make it too complicated. Simply
chose a pace that brings you near exhaustion on the final
20-second rep; you should become more fatigued with each rep.
Increase the pace as your condition improves. It's always
better to underestimate your ability at the start. Begin a
little slower than you think you can handle, and then adjust
the pace from workout to workout. Don't attempt
high-intensity intervals unless you are in good condition;
they're not appropriate for beginners. Note the medical
warning which follows.]
Warning
The Tremblay group and Dr.
Tabata, in his e-mail response to Richard Winett, emphasize
this warning: "High-intensity
exercise cannot be prescribed for individuals at risk for
health problems or for obese people who are not used
to exercise."
NOTE: This article was
written by Clarence Bass.
