HIIT Exercise and Its Effects on the Body and Brain

June 08, 2017

HIIT Exercise and Its Effects on the Body and Brain

Like speed dating, "high intensity interval training" (HIIT) is an innovation that's become popular in the twenty-first century because it's quick, it's convenient, it's fun -- and it works.

Ambitious, self-motivated people hate wasting time. We know that time is one of our most valuable assets, so we're always looking for efficiencies and productivity gains. If there's a quicker, better way of doing something we'll find it.

A single session of HIIT can last as little as four minutes -- or as long as thirty minutes. It involves a brief warm-up followed by short bursts of flat-out exercise -- such as sprinting -- alternated with even briefer periods of low-intensity activity, such as walking or jogging. Finally, when the session ends, the participant can relax and cool down.

Reaping the Benefits

The benefits of HIIT are that it burns calories and fat, improves your endurance, boosts metabolism and is good for the heart.

There's also the important knock-on effect of "what's good for the body is also good for the brain." When you improve oxygen flow to the brain you can think more quickly and effectively.

That's not all! In contrast to other exercise programmes, HIIT leaves you with more time to work creatively. People in business or academic life can't spend too many hours in the gym or on the sports field. HIIT is the neatest solution for achieving a balanced lifestyle and getting exercise without sacrificing valuable time.

The Styles and Variations of HIIT

Sports scientists have developed several styles of HIIT, with variety in the duration, intensity and type of exercise involved. One of the first was the "Tabata Protocol," developed by the Japanese sports scientist Izumi Tabata, based on pioneering work by Olympic speed skating coach Irisawa Koichi.

Nothing could be simpler than what is now called (and trademarked as) "Tabata." It consists of 20 seconds of intense exercise followed by 10 seconds of rest. Repeated 8 times it gives you "Four Minute Fitness, Scientifically Proven."

Dr. Tabata has shown that HIIT gets you "fitter, faster, than any other workout." In clinical trials he showed that just four minutes of "Tabata" produced a 28 percent increase in anaerobic fitness, compared to no improvement at all after an hour's cycling.

For success with "Tabata" you need to maximise the intensity of the 20-second periods of exercise, for example by maintaining 85rpm on an exercise bicycle for each of the eight periods of intensity. Most people find this exhausting -- but that's the secret. By doing it you're pushing your own boundaries, yet not dangerously so because the periods are short and the body recovers quickly.

HIIT Lite

An important variation of HIIT has been developed by Professor Martin Gibala at McMaster University in Canada. After publishing a full-on exercise regimen for athletes, he and his team designed an alternative version for people who've been relatively sedentary for a year or so.

The cut-down "Gibala" method involves a three-minute warm up followed by 60-second bursts of exercise at 60 percent peak power, alternating with 60 seconds of recovery.

You have to bear in mind that instruments are available in the laboratories where these experiments take place, so "60 percent peak power" can be calculated precisely. It means the subject is performing to about 80–95% of heart rate reserve, that is: the difference between maximum heart rate and resting heart rate. In unmonitored situations you would need to estimate the level for yourself.

Fighting the Sedentary Lifestyle

A sedentary lifestyle has a negative effect on both muscle oxidative capacity and insulin sensitivity.

Your muscles' oxidative capacity is a measure of how much oxygen they can use, expressed as microlitres of oxygen consumed per gram of muscle per hour. We lose muscle mass naturally when we grow old, but equally our muscle mass can shrink in the prime of life if we don't get sufficient exercise. To be in the best shape your muscles need to have a high oxidative capacity.

A related factor is insulin sensitivity -- an indication of how sensitive the body is to insulin, the hormone which allows the body to use sugar (glucose) from carbohydrates in food. If you have insulin resistance it's a sure sign you're having difficulty metabolising glucose. If this imbalance goes too far it can lead to Type 2 diabetes, a condition that comes from being overweight and leading a sedentary lifestyle.

HIIT -- and especially what we're calling "HIIT Lite" -- can help any otherwise healthy person overcome the problems of muscle loss and reduced insulin sensitivity. Make no mistake, HIIT Lite is still quite demanding, but it's not going to prompt a heart attack -- as full-on HIIT could do if you suddenly try it after a long period without any exercise at all.

HIIT for Diabetics

If you're diabetic, it's essential to consult your doctor before embarking on a regimen of HIIT. Although it can be beneficial, there is the danger that increased insulin sensitivity will lead to hypoglycemia if you're already taking doses of insulin with an insulin pen.

With hypoglycemia, blood sugar levels become dangerously low: falling below a set point of 4 millimoles per litre (72 milligrams per decilitre). Usually, the problem can be solved by obtaining an insulin pen which can give half units instead of full ones. That's good: it means the exercise is restoring your body's natural metabolism.

Help from Other Factors

Because HIIT is strenuous -- if only in short bursts -- any help is welcome. So where can you find it?

Personal Trainer: If you can afford a personal trainer, he or she will guide, encourage and motivate you to perform your HIIT training so you get maximum benefit from it. Clearly, a trainer doesn't need to be full-time if your workouts are as short as (say) twenty minutes a day.

Group Aerobics: You can get mutual encouragement from friends if you take part in HIIT group aerobics. Large corporations should consider providing the right facilities to enable such groups to function.

Music: Even if (or especially if) you're doing HIIT on your own, there's a scientific basis for having loud, inspirational music in the background. A paper by Professor Gibala and others in 2015 was called "Music Enhances Performance and Perceived Enjoyment of Sprint Interval Exercise."

Nootropics: There's nothing in tablet form which can replace HIIT, but certain nootropics can augment the process, making it even more beneficial. A good example is Green Tea or Matcha. Again, Professor Gibala and his team have written about it, in another 2015 paper: "Green Tea Extract Ingestion Decreases Respiratory Exchange Ratio During Recovery From High-intensity Interval Exercise."

Chilling Out

The green tea researchers concluded that a single dose of green tea extract (GTE) reduced the "respiratory exchange ratio" (RER) during recovery from what they describe as "an acute bout of high-intensity interval exercise."

The RER is the ratio of the net output of carbon dioxide to the simultaneous net uptake of oxygen. It's beneficial to have a lower ratio because it means you're burning more fat and less carbohydrate. An RER of 0.70 typically indicates fat as the main fuel source, whereas an RER of 0.85 indicates a mix of fat and carbohydrates, while a value of 1.00 or higher shows that carbohydrate is the predominant fuel source.

So the recommendation is: drink green tea or matcha, start HIIT using the safest method which we've called HIIT Lite, and chill out. In no time at all you're be back at work, refreshed and raring to go.




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