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Lose Weight Faster With High Intensity Interval
by David Petersen
http://www.bossfitness.com
Lose Weight Faster With High Intensity Interval Training
(HIIT)
The one of the latest buzzwords in fitness and weight loss
circles is High Intensity Interval Training or HIIT. This
method of exercise has the potential to allow an exerciser
to lose weight faster that any other form of "aerobic"
exercise. Although interval training is not a new concept
in the field of sports conditioning, it has recently
become a popular exercise form for general conditioning
and weight loss. This article provides some basic
information on HIIT and explains why this form of exercise
is so effective for weight loss.
The concept of power output
To fully understand the many benefits of HIIT it is
important to first understand some basic physics and the
concept of power. Generally speaking, power is a measure
of the ability to perform work per unit time (Work/time).
Work is defined as the amount of force required to move an
object a certain distance (Force x Distance). So power is
defined by the following formula: Power = Force x
Distance/time. If you recall that velocity (speed) is
equal to distance divided by time (Distance/time), then it
is easy to see that power is actually a measure of how
fast you generate force.
Power output and energy expenditure
Obviously from the previous explanation, it should be
clear that the amount of energy required to perform a task
is directly dependent on the power required to do so. So
if we now apply this concept specifically to human
exercise, we recognize that muscles use chemical energy
produced from the food we eat to generate power. Consider
the muscle power required to walk 3 miles per hour and
that required to run at 11 miles per hour. The muscle
power required in each example is strictly dependent on
the speed since the force (body weight) being moved
changes very little and essentially remains constant
(assuming sufficient hydration). It is possible however to
regulate power output by other variables other than speed
by manipulating the amount of force (wearing a weighted
vest) or increasing the resistance to movement like
increasing the gradient of a treadmill or running up hills.
What is HIIT?
HIIT involves performing bouts of high intensity running
(1-3 minutes) separated by recovery periods of walking for
about the 2-3 times the duration of the running bout. The
work: recovery ratio should therefore be 1:2 or 1:3. The
intensity of the running portion should be near your VO2
max (maximal oxygen uptake). Since most casual exercisers
and those looking to lose weight rarely know their VO2
max, is may be helpful to use a perceived effort scale of
1-10 to regulate intensity; with 1 representing no effort,
and 10 representing absolute maximal effort. Aim for about
8-9 on the effort scale. Note that HIIT describes what it
is - HIGH Intensity Interval Training so before you begin
such a regime it is advisable to have yourself cleared by
a physician.
How do I begin HIIT?
There are no hard and fast rules to HIIT other than those
mentioned above, so this article will not aim to provide a
strict program of exact times and durations. The basic
principle of HIIT is to manipulate intensity to increase
power output and accelerate weight loss. Initially if you
are just beginning HIIT, your work sessions may be much
shorter than 2-4 minutes ~ work your way from whatever you
can handle to the goal duration. As you become more
conditioned, you may also start to increase the intensity
of the sessions by aiming for the higher end of the
perceived effort scale or reducing the recovery walking
periods or both. If you plan on exercising on a treadmill
or elliptical machine, an excellent way to perform HIIT is
to choose an intense interval or hill program. If you
prefer to get the session over quickly as possible (like
me), you can manually adjust the speed and incline
randomly depending on your perception of effort. If you
are sadistically self-destructive however, you may
try "running the hills and walking the flats" on a
treadmill ~ this will greatly increase your power output
and energy expenditure. Experiment with these techniques
of manipulating the intensity of your workout and
depending on your level of fitness (or patience!), the
entire interval training session should last from about 10-
20 minutes in duration.
How does HIIT allow for faster weight loss than
traditional "aerobic exercise"?
HIIT is a big "bang for the buck" exercise modality
compared to traditional extended duration aerobic exercise
like walking, jogging and running. Walking requires a
relatively low power output and high speed running simply
cannot be sustained for very long periods of time. The
great benefit of HIIT is that the low intensity walking
bouts that separate the high intensity bouts allow for a
much greater power output and caloric expenditure,
providing much more "value for time". Depending on the
intensity of the session, it may be possible to burn the
same number of calories in a HIIT session as a
walking/cycling session many times longer in duration.
HIIT spares muscle mass and maintains metabolism
Recall from an earlier article on our website Spare Muscle
Mass and Power, Lose the Fat where we discussed how HIIT
helps avoid the muscle wasting effects associated with
continuous low intensity exercise such as jogging and
walking. HIIT helps spare valuable lean muscle mass which
is a key determinant of your RMR or Resting Metabolic
Rate. Simply put, a higher muscle mass will cause you to
expend more energy even while you sleep! The technical
term for this muscle wasting effect is "protein
sloughing", caused by extended periods of elevated
cortisol levels. Cortisol is a hormone released from the
adrenal gland during all forms of stress including
exercise. Although cortisol is crucial for a person to
adapt to stressful stimuli, a negative side-effect is its
direct muscle wasting effect. Cortisol stimulates muscle
protein breakdown in order to increase the amount of free
amino acids (protein building blocks) in the blood. The
majority of these amino acids are used for the
remanufacturing of glucose (gluconeogenesis) in the liver
to maintain blood sugar levels. While some personal
trainers and exercise physiologists may argue that the
increased exercise intensity (stress) of HIIT causes a
higher increase in cortisol, the important factor to
remember is that the duration that the hormone levels
remains elevated is significantly shorter than in extended
lower intensity aerobic exercise.
How can I lose fat when I'm burning mostly carbohydrates
with HIIT?
Remember even though HIIT is a high intensity form
exercise, relying heavily on the metabolism of
carbohydrate, weight loss is determined by energy balance.
In other words, if on a daily basis you consume less
energy than you expend, you will lose weight regardless of
the "primary fuel source" of your exercise bout. An HIIT
session that decreases your carbohydrate stores (muscle
and liver glycogen) simply means that more calories from
subsequent meals will be will be directed toward
replenishing glycogen stores, and less will be directed
toward fat storage. It is only after glycogen stores have
been replenished that excess calories can be directed
toward the manufacturing and storage of fat. Also, caloric
expenditure continues for several hours after a bout of
high intensity exercise, as energy is required in the
recovery process.
In conclusion, this article has explained and highlighted
the benefits associated with the use of HIIT for weight
loss. Other benefits such as faster fitness improvements
and immune system maintenance associated with HIIT have
not been covered in this article, but may be discussed in
future articles on our site. Clearly if the goal is to
lose weight fast and boost metabolism by sparing muscle,
then HIIT is the ideal form of exercise.
David Petersen is a Personal Trainer/Certified Strength
and Conditioning Specialist and the owner and founder of
B.O.S.S. Fitness Inc. based in Oldsmar, Florida. More
articles and information can be found at
http://www.bossfitness.com
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