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| Image from WhyExercise.com |
No Time for Exercise? Try High-Intensity Interval
Training (HIT)
FROM:
Isagenix Health
April 24, 2013
With high-intensity interval
training, you reap the benefits of exercise without spending hours at the gym.
We all know that exercise is good
for us, and we’ve heard that we should be getting 30 to 60 minutes per day most
days of the week. But in today’s fast-paced world, where the demands of work,
child care, and home maintenance seem to endlessly steal from our
ever-shrinking depot of availability, finding the time to meet these
recommendations can be quite a challenge.
What if there was a form of exercise
that would allow you to reap the many health benefits of regular physical
activity in just a quarter of the time? According to a recent review written by
Australian researchers, high-intensity interval training (HIT) is a form of
exercise that may do exactly that. Mounting evidence cited by the authors
suggests that HIT is a time-efficient and effective alternative to traditional
endurance exercise for boosting weight loss, aerobic stamina, and
cardiovascular and metabolic health (1).
What is HIT?
HIT involves alternating intense
bouts of exercise, ranging from 30 seconds to several minutes, with recovery
periods spanning one to five minutes. For example, a cyclist might incorporate
HIT by pedaling as fast as possible for 30 seconds against a strong resistance,
lowering the resistance and leisurely cycling for 4 minutes, and then repeating
this alternating schedule 4 to 6 times per session.
Such a training regimen adds up to
about 20 to 25 minutes of exercise, which has shown substantial benefits when
performed as few as three times per week (2). Just 2.5 hours of HIT completed
over a total of 2 weeks has demonstrated benefits that are equivalent to 10.5
hours of continuous moderate exercise.
What are the benefits of HIT?
1. Improved Body Composition
Many turn to traditional endurance
exercise in the attempt to lose weight and improve their physical appearance,
yet HIT may deliver even better results. HIT has been shown to reduce body fat,
particularly abdominal fat (1, 3). In comparison with continuous moderate
exercise, HIT increases energy expenditure and fat burning to a greater extent
in the minutes and hours after a workout (1). This “after burn” is formally
known as excess post-exercise oxygen consumption (EPOC) and reflects the
body’s extra use of energy to replenish depleted fuel stores, repair cells, and
restore hormonal and other body systems to their pre-exercise state. (This is
also prime time for consuming IsaLean Shake or IsaLean
Pro to fuel greater muscle growth!)
In addition to increasing EPOC to a
greater extent than traditional endurance exercise, HIT also promotes greater
releases of growth hormone (4). This transient increase in growth hormone may
be important during the post-workout period when muscles are primed for growth.
During exercise, muscle damage occurs and muscle synthesis stops. Spikes of
growth hormone promoted by HIT may quickly mitigate protein breakdown after
exercise and serve as a signal for muscle growth (5).
HIT may also help preserve muscle
mass in other ways. During long bouts of steady-state exercise, glycogen (the
storage form of sugar) becomes depleted, and the body begins to break into its
muscle reserves to get protein that can be used for energy. Because HIT relies
on intervals of intense exercise broken up by intervals of more leisure, less
intense exercise, muscle reserves are better preserved. Together, increases in
growth hormone and the protection of muscle protein results in the preservation
of muscle mass, which keeps metabolism running high and supports greater fat
loss over the long term.
2. Improved Cardiovascular Health
It is well known that several different
markers of cardiovascular health—such as VO2 max, blood vessel wall elasticity,
and blood pressure— can be improved by steady-state endurance training. HIT has
also demonstrated equivalence or superiority over traditional endurance
training in improving these markers (1). VO2 max is a measurement that
determines the physical fitness of a person. It detects the maximum ability of
the body to transport and use oxygen during exercise. The higher the VO2 max,
the more efficiently a person can get oxygen to working muscle, and the more
rapidly this oxygen can be used to power performance. Because the heart is a
muscle that can be strengthened by exercise, HIT can improve the heart’s
ability to contract, increasing the amount of blood and oxygen that can be pumped
to muscle. HIT has been shown to increase VO2 max to an even greater extent
than traditional endurance training (1).
An important indicator of
cardiovascular health is blood vessel wall elasticity, often referred to as
endothelial function; the better the endothelial function, the greater the
capacity of the blood vessel to expand or contract when necessary. Unhealthy
arteries tend to be harder and less flexible. HIT has also demonstrated
improvement in endothelial function and in reduction of blood pressure (1).
In addition to increasing VO2 max,
improving endothelial function, and lowering blood pressure, HIT may help lower
total cholesterol and LDL cholesterol (the “bad” cholesterol), while also
increasing blood levels of HDL cholesterol (the “good” cholesterol) when
combined with a balanced diet. Improved levels of cholesterol, as well as
better blood pressure and endothelial function, can lead to reduced
cardiovascular disease risk.
3. Improved Metabolic Health
Another well-known benefit of regular
exercise is improved blood sugar control. Exercising muscle has a high demand
for sugar as a fuel source. The more intense the exercise, the more muscle
relies on sugar from the bloodstream and stored forms of sugar (glycogen) for
energy. HIT has been shown to be effective in reducing blood sugar, and has
also been shown to improve insulin sensitivity (1).
As a gatekeeper of sugar’s entry
into body cells, the hormone insulin has a primary role in keeping blood sugar
levels within a healthy range. Resistance to insulin ultimately leads to high
blood sugar levels and impaired energy production. The ability of HIT to
enhance insulin sensitivity helps ensure the delivery of sugar to the cells
that need it as well as proper blood sugar control.
4. Improved Aerobic Stamina and
Exercise Performance
Although steady-state endurance
training is notorious for improving aerobic stamina and conditioning, studies
show that HIT is also an effective exercise strategy for achieving this goal.
Not only does HIT increase VO2 max, it also increases time to exhaustion during
exercise. In one study, the length of time that a group of eight athletes were
able to cycle at 80 percent VO2 max nearly doubled—from 26 minutes to 51
minutes—after undergoing six HIT sessions over two weeks (6).
Another factor that contributes to
endurance performance is the ability of the muscle to store sugar as glycogen.
Glycogen is used for energy as exercise progresses. There is a limit to the
amount of glycogen that each person can store, but HIT has been shown to
increase this amount (1, 2, 7). HIT also causes muscle to lower the rate at
which it uses glycogen for energy, resulting in a greater reliance on the use
of fat for fuel. Increasing and preserving energy stores in the form of
glycogen will extend time to exhaustion, ultimately improving exercise
performance (1, 2, 7).
HIT is for (Almost) Everyone
Most people can benefit from HIT.
Studies have shown that it is safe and effective for those with health
conditions such as diabetes and cardiovascular disease, and offers numerous
advantages for healthy people simply looking to save time or switch up their
workouts (1). Even professional endurance athletes are using HIT to improve
performance by incorporating it alongside traditional endurance exercise in a
comprehensive training program.
HIT is a fun way to break up the
monotony of conventional workouts, and according to the Australian researchers,
may even be easier to stick to than traditional endurance training. HIT can
yield substantial health and fitness benefits with minimal time commitments,
making it the perfect prescription for those who don’t have 30 to 60 minutes
every day to meet the current exercise recommendations. However, before
starting HIT or any other exercise program, a consultation with a person’s
physician is advised to determine if appropriate.
References
2. Gibala MJ. High-intensity
interval training: a time-efficient strategy for health promotion? Curr
Sports Med Rep. 2007 Jul;6(4):211-3. Review.
4. Pritzlaff CJ et al. Impact of acute exercise
intensity on pulsatile growth hormone release in men. J Appl Physiol. 1999 Aug;87(2):498-504.
5. Post-exercise hypertrophic
adaptations: A re-examination of the hormone hypothesis and its applicability
to resistance training program design. J Strength Cond Res.
2013 Feb 25. [Epub ahead of print]
6. Burgomaster KA, et al. Six sessions of sprint
interval training increases muscle oxidative potential and cycle endurance
capacity in humans. J Appl Physiol. 2005 Jun;98(6):1985-90. Epub
2005 Feb 10.
