Steady State Cardio 5 X More Effective Than HIIT?
High Intensity Interval Training, or HIIT for short, has
been promoted as one of the most effective training methods
ever to come down the pike, both for fat loss and for
cardiovascular fitness. One of the most popular claims for
HIIT is that it burns “9 times more fat” than conventional
(steady state) cardio. This figure was extracted from a
study performed by Angelo Tremblay at Laval University in
1994. But what if I told you that HIIT has never been
proven to be 9 times more effective than regular cardio…
What if I told you that the same study actually shows that
HIIT is 5 times less effective than steady state cardio???
Read on and see the proof for yourself.
“There are lies, damned lies, and then there are
statistics.”
- Mark Twain
In 1994, a study was published in the
scientific journal Metabolism by Angelo Tremblay
and his team from the Physical Activity Sciences Laboratory
at Laval University in Quebec, Canada. Based on the results
of this study, you hear personal trainers across the globe
claiming that “HIIT burns 9 times more fat than steady
state cardio.”
This claim has often been
interpreted by the not so scientifically literate public as
meaning something like this: If you burned 3 pounds of fat in
15 weeks on steady state cardio, you would now burn 27 pounds
of fat in 15 weeks (3 lbs X 9 times better = 27 lbs).
Although it’s usually not stated as
such, frankly, I think this is what some trainers want you to
believe, because the programs that some trainers promote are
based on convincing you of the vast superiority of HIIT and the
“uselessness” of low intensity exercise.
Indeed, higher intensity exercise
is more effective and time efficient than lower intensity
exercise. The question is, how much more effective? There’s no
evidence that the “9 times more fat loss” claim is true outside
the specific context in which it was mentioned in this
study.
In order to get to the bottom of
this, you have to read the full text of the research paper and
you have to look very closely at the results.
13 men and 14 women age 18 to 32
started the study. They were broken into two groups, a high
intensity intermittent training program (HIIT) and a steady
state training program which they referred to as endurance
training (ET).
The ET group completed a 20 week
steady state aerobic training program on a cycle ergometer 4
times a week for 30 minutes, later progressing to 5 times per
week for 45 minutes. The initial intensity was 60% of maximal
heart rate reserve, later increasing to 85%.
The HIIT group performed 25-30
minutes of continuous exercise at 70% of maximal heart rate
reserve and they also progressively added 35 long and short
interval training sessions over a period of 15 weeks. Short
work intervals started at 10 then 15 bouts of 15 seconds,
increasing to 30 seconds. Long intervals started at 5 bouts of
60 seconds, increasing to 90 seconds. Intensity and duration
were progressively increased over the 15 week period.
The results: 3 times greater fat
loss in the HIIT group
Even though the energy cost of the exercise performed in
the ET group was twice as high as the HIIT group, the sum
of the skinfolds (which reflects subcutaneous body fat) in
the HIIT group was three times lower than the ET group.
So where did the “9 times greater
fat loss” claim come from?
Well, there was a difference in
energy cost between groups, so in order to show a comparison of
fat loss relative to energy cost, Tremblay wrote,
“It appeared reasonable to
correct changes in subcutaneous fat for the total cost of
training. This was performed by expressing changes in
subcutaneous skinfolds per megajoule of energy expended in each
program.”
Translation: The subjects did not lose 9 times more body
fat, in absolute terms. But hey, 3 times more fat loss?
You’ll gladly take that, right?
Well hold on, because there’s more.
Did you know that in this oft-quoted study, neither group lost
much weight? In fact, if you look at the charts, you can see
that the HIIT group lost 0.1 kg (63.9 kg before, 63.8 kg
after). Yes, the HIIT group lost a whopping 100 grams of weight
in 15 weeks!
The ET group lost 0.5 kilograms
(60.6 kg before, 60.1 kg after).
Naturally, lack of weight loss
while skinfolds decrease could simply mean that body
composition improved (lean mass increased), but I think it’s
important to highlight the fact that the research study from
which the “9 times more fat” claim was derived did not result
in ANY significant weight loss after 15 weeks.
Based on these results, if I wanted to manipulate
statistics to promote steady state cardio, I could go
around telling people, “Research study says steady state
cardio (endurance training) results in 5 times more weight
loss than high intensity interval training!” Or the
reverse, “Clinical trial proves that high intensity
interval training is 5 times less effective than steady
state cardio!”
Mind you, THIS IS THE SAME STUDY
THAT IS MOST OFTEN QUOTED TO SUPPORT HIIT!
If I said 5 X greater weight loss
with steady state, I would be telling the truth, wouldn’t I?
(100 grams of weight loss vs 500 grams?) Of course, that would
be misleading because the weight loss was hardly significant in
either group and because interval training IS highly effective.
I’m simply being a little facetious in order to make a point:
Be careful with statistics. I have seen statistical
manipulation used many times in other contexts to deceive
unsuspecting consumers.
For example, advertisements for a popular fat burner claim
that use of their supplement resulted in twice as much fat
loss, based on scientific research. The claim was true. Of
course, in the ad, they forget to tell you that after six
months, the control group lost no weight, while the
supplement group lost only 1.0 kilo. Whoop de doo! ONE KILO
of weight loss after going through a six month supply of
this “miracle fat burner!”
But I digress…
Back to the HIIT story - there’s
even more to it
In the ET group, there were some
funky skinfold and circumference measurements. ALL of the
skinfold measurements in the ET group either stayed the same or
went down except the calf measurement, which went up.
The girths and skinfold
measurements in the limbs went down in the HIIT group, but
there wasn’t much difference between HIIT and ET in the trunk
skinfolds. These facts are all very easy to miss. I didn’t even
notice it myself until exercise physiologist Christian Finn
pointed it out to me. Christian said,
“When you look at the changes in
the three skinfold measurements taken from the trunk, there
wasn’t that much difference between the steady state group
(-6.3mm) and the HIIT group (-8.7 mm). So, much of the
difference in subcutaneous fat loss between the groups wasn’t
because the HIIT group lost more fat, but because the steady
state group actually gained fat around the calf muscles. We
shouldn’t discount simple measurement error as an explanation
for these rather odd results.”
Christian also pointed out that the two test groups were
not evenly matched for body composition at the beginning of
the study. At the beginning of the study, the starting body
fat based on skinfolds in the HIIT group was nearly 20%
higher than the ET group. He concluded:
“So while this study is
interesting, weaknesses in the methods used to track changes in
body composition mean that we should treat the results and
conclusions with some caution.”
One beneficial aspect of HIIT that most trainers forget to
mention is that HIIT may actually suppress your appetite,
while steady state cardio might increase appetite. In a
study such as this, however, that can skew the results. If
energy intake were not controlled, then some of the greater
fat loss in the HIIT group could be due to lowered caloric
intake.
Last but not least, I’d like to
highlight the words of the researchers themselves in the
conclusion of the paper, which confirms the effectiveness of
HIIT, but also helps put it in perspective a bit:
“For a given level of energy
expenditure, a high intensity training program induces a
greater loss of subcutaneous fat compared with a training
program of moderate intensity.”
“It is obvious that high intensity exercise cannot be
prescribed for individuals at risk for health problems or
for obese people who are not used to exercise. In these
cases, the most prudent course remains a low intensity
exercise program with a progressive increase in duration
and frequency of sessions.”
In conclusion, my intention in
writing this article wasn’t to be controversial, to be a
smart-alec or to criticize HIIT. To the contrary, additional
research has continued to support the efficacy of HIIT for fat
loss and fitness, not to mention that it is one of the most
time efficient ways to do cardiovascular training.
I have recommended HIIT for years
in my Burn The Fat, Feed The
Muscle program, using a 1:1 long
interval approach, which, while only one of many ways to do
HIIT, is probably my personal favorite method. However, I also
recommend steady state cardio and even low intensity cardio
like walking, when it is appropriate.
My intentions for writing this
article were four-fold:
1. To encourage you to question
where claims come from, especially if they sound too good to be
true.
2. To alert you to how advertisers might use research such as
this to exaggerate with statistics.
3. To encourage the fitness community to swing the pendulum
back to center a bit, by not over-selling the benefits of HIIT
beyond what can be supported by the scientific research.
4. To encourage the fitness community, that even as they praise
HIIT, not to condemn lower and moderate intensity forms of
cardio.
As the original author of the 1994 HIIT study himself
pointed out, HIIT is not for everyone, and cardio should be
prescribed with progression. Also, mountains of other
research has proven that walking (GASP! - low intensity
cardio!) has always been one of the most successful
exercise methods for overweight men and women.
There is ample evidence which says
that obesity may be the result of a very slight daily energy
imbalance, which adds up over time. Therefore, even a small
amount of casual exercise or activity, if done consistently,
and not compensated for with increased food intake, could
reverse the obesity trend. HIIT gets the job done fast, but
that doesn’t mean low intensity cardio is useless or that you
should abandon your walking program, if you have the time and
if that is what you enjoy and if that is what’s working for you
in your personal situation.
The mechanisms and reasons why HIIT
works so well are numerous. It goes way beyond more calories
burned during the workout.
Train hard and expect success,
Tom Venuto, NSCA-CPT, CSCS
Fat Loss Coach
Burn
The Fat, Feed The Muscle
Reference: Tremblay,
Angelo, et al. Impact of exercise intensity on body fatness and
skeletal muscle metabolism. Metabolism. Vol 43. no 7 (July). Pp
814-818. 1994..
About the Author:
Tom Venuto is a natural
bodybuilder, certified personal trainer and freelance fitness
writer. Tom is the author of "Burn the Fat, Feed The Muscle,”
which teaches you how to get lean without drugs or supplements
using secrets of the world's best bodybuilders and fitness
models. Learn how to get rid of stubborn fat and increase your
metabolism by visiting: Burn The Fat,
Feed The Muscle
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