High Intensity Interval Training also called Sprint Interval training (SIT) is a type of exercise workout that sees you engage in intense anaerobic exercise for short periods of time, followed by rest periods where you either relax or do easier exercise.
These short periods of intensive exercise are believed to burn fat faster than low intensity longer lasting exercise programmes.
Anaerobic exercise is designed to promote lactic acid fermentation – the body state that sees blood sugars glucose, fructose and sucrose converted to cellular energy , also known as fat burning. To reach this state exercise needs to be intense.
Aerobic exercise by contrast is anything that requires a good oxygen supply and includes less intensive exercise such as walking jogging rowing and similar. Essentially this is any other type of cardio exercise that gets the blood pumping and challenges your stamina levels long term.
Interval training is popular with athletes looking to promote performance, strength and stamina. It helps athletes build fitness levels and last longer at the sport and is a training method used by long distance runners, cyclists and similar.
It is also popular with body builders because it helps burn fat and promotes strength and muscle building.
Health Benefits of HIIT
According to research, HIIT increases the capacity of fat burning and builds muscle as well as create other medical benefits. When a clinical test was carried out on women, it indicated that two weeks of high-intensity aerobic interval training increased the capacity for fat oxidation during exercise.
The women completed a series of sessions comprising of 10 four-minute periods of intensive exercise, interspersed with two minutes breaks. In summary, seven sessions of HIIT over 2 weeks resulted in marked increases in whole body and skeletal muscle capacity for fatty acid oxidation during exercise in moderately active women.
Other clinical trials carried out by the University of Edinburgh and Stockholm on 16 young men found that HIIT reduced insulin levels and may be helpful in the prevention and treatment of diabetes.
According to the research,
The efficacy of a high intensity exercise protocol, involving only ~250 kcal of work each week, to substantially improve insulin action in young sedentary subjects is remarkable
They went further in saying that,
This novel time-efficient training paradigm can be used as a strategy to reduce metabolic risk factors in young and middle aged sedentary populations who otherwise would not adhere to time consuming traditional aerobic exercise regimes
In other words, the fact that this exercise method saves so much time means that more people will do it and it has medical benefits.
So How Do You Do HIIT?
There many different exercises you can do but a good example is with an exercise bike. First a brief warm up phase of 5 minutes or and then perform six to eight 30 seconds of hard cycling – as fast as you can possibly go, interspersed with 90 seconds of easy cycling between each energy burst. Once you have completed this series, your HIIT is done!
You can transfer this idea to running, squats, rowing or any other type of exercise. The idea is that you do this each day as a regular part of your routine and it not only boosts your health, it helps you lose weight and burn fat too.
There is no specific formula for HIIT but another common formula is for exercise to be carried out on a 2:1 ratio. For example, runners can do 30 – 40 seconds of hard sprinting followed by 15 – 20 seconds of walking or jogging.
The Origins of HIIT
The origins of High Intensity Interval Training lie in sports training. In the 1970s Peter Coe, father of runner and Olympic mastermind Seb Coe, developed interval training when he was training Seb Coe, featuring repeated 200m sprints with a 90 second break in between. These ideas were based on the work of German University professor and Sports coach Woldemar Geschler and found effective for boosting sports performance and strength.
HIIT came to the public’s attention following a BBC Horizon programme in 2012 when TV doctor Michael Moseley ( of 5:2 diet plan ) was put on an HIIT regime by professor Jamie Timmons, professor of Aging Biology from the University of Birmingham. The regime was to carry out three bursts of 20 seconds flat out cycling interspersed with two minutes of gentle cycling , carried out thee times a week , over a few weeks.
Results were encouraging and included improved insulin sensitivity and weight loss.
A clinical trial led by Jamie Timmons is now being carried out on 300 volunteers at the University of Birmingham to look into whether 3 minutes of HIIT delivers the same results as longer methods of exercise such as running or going to the gym. The aim is to test whether HIIT is safe and if it is safe when undertaken on a long-term basis by ordinary non-athletic people.
Dangers of HIIT
HIIT has been making the news just recently, most notably because BBC presenter Andrew Marr, who suffered a stroke after working out on his rowing machine, was allegedly following an HIIT regime. If this is true, then it seems that HIIT is something that you do need to be careful with but of course it is possible that it was coincidental.
People can experience life-threatening conditions while exercising – such as heart attacks, which come on while out jogging and similar. Even professional super fit sportsmen can inexplicably collapse on the sports field.
Who can forget Fabrice Muamba the professional footballer who collapsed in a football match last year and had to be revived on the pitch? It was found that he was suffering from an undetected medical condition, so it does not necessarily follow that Andrew Marr’s experience means that HIIT is bad. Adverse effects can happen to anyone.
Is HIIT Safe?
The NHS is cautious in recommending HIIT as an exercise model for all. Most of the testing has been carried out on young, already fit people, and further research is need to establish exactly how suitable HIIT is for different groups of people ; especially older people, those with health problems and those who may not be that fit to begin with.
People who have high blood pressure and existing heart conditions will need to be extremely cautious.
The NHS are recommending that safe levels of conventional exercise are preferable. Their current recommendations are that 30 minutes of physical activity 5 times a week is optimum for health, based on rigorous reviewing of all the evidence surrounding HITT and after discussions with experts.
Non-intensive methods of exercise such as jogging, walking and swimming are considered safe.
Conventional exercise carried out over the course of a week is good for your mental health too and has absolutely no adverse side effects.
So What Happened to Andrew Marr
Andrew Marr is now in recovery since his stroke and is back on TV for the first time since the accident in January 2013. He says that he had followed the advice to
take very intensive exercise in short bursts – because that’s the way to health
He was quoted in the Guardian as saying,
I went on a rowing machine and gave it everything I had… and had a strange feeling afterwards
The strange feeling turned out to be a stroke that Marr was lucky to survive with no major side effects.
So was HIIT the cause?
Yes and no. Andrew Marr had undoubtedly been overdoing the exercise and effort but has blamed the accident in part on his stress levels and overwork. He has also said that he is in no hurry to get back on the rowing machine!
Perhaps this form of exercise is simply too intensive for some people despite the health benefits?
Does HIIT Burn Fat?
HIIT does appear to burn fat and it has numerous health benefits including a reduction of adipose tissue and improved insulin sensitivity. If you lack the time to engage in 30 minutes exercise a day, then HIIT may seem like the answer to achieving fitness without actually having to do much.
Exercise increases the speed of the metabolism and this effect continues to work after the exercise is over and you are at rest. All exercise has this effect but HIIT appears to be more efficient and the difference with HIIT over conventional exercise is that you “get much more from your effort”.
So Should I Carry Out HIIT Myself?
If you have any existing medical condition, you need to see your doctor for advice. You need to be careful not to “overdo “and you may need to build up general levels of fitness before you start training.
The Heart And Stroke Foundation, urges you to exercise caution. They advise that you “should be able to exercise for at least 20 to 30 minutes at 85% to 90% of your estimated maximum heart rate for your age, without exhausting yourself or having problems”
They offer the following advice.
- HIIT is extremely demanding on your body so you need to start low and build up fitness. Begin your sessions at no more than 10 minutes and work up to longer duration. 30 minutes HIIT is the maximum.
- Always take time to warm up and cool down for at least 5 minutes around your HIIT
- Stick to your rest period intervals. Don’t increase the length of the intense exercise periods and if you can perform the whole session and feel like doing more, increase your intervals or intensity then.
- Stop immediately if you notice chest pains or experience difficulties in breathing. Seek medical advice if symptoms do not immediately stop.
- If you feel faint, briefly cool down then lie down on your back and raise your legs onto a chair or against a wall in a raised position
- Your heart needs to slow down during your rest periods and if you are still breathless at the end of your recovery period, you need to take the intensive periods more gently. You are aiming to feel exhausted by the end of the session but it is important to remain in control.
- Get the advice of a fitness trainer who may be able to set up the ideal HIIT programme for your level of fitness. Ask your doctor for advice
HIIT for Fat Loss – Our Verdict
HIIT undoubtedly has numerous health benefits and many people are attracted to its convenience as a fast way to exercise for weight loss.
However, you will need to proceed with caution and if you are not already in good shape, then you will need to get fit before you start and take care not to overdo it. Perhaps get a health check and ask your doctor’s advice before you start.
HIIT as an exercise method for everyone is still under investigation – after all this was devised for athletes originally, and although results are extremely promising, no firm conclusion has yet been reached.
For now, perhaps the guidelines laid down by the NHS maybe safer. Exercising 30 minutes a day five times a week is better for you and although it may take longer, taking a bit of “me” time and getting fit doing something you enjoy like dancing or cycling can be fun.
HIIT does sound like mostly pain over pleasure and even if it is a fast method of exercise, will it actually save you any time?
You are going to need to change clothes and take a shower after you have finished and all this takes time. If you lack time to do conventional exercise, then it doesn’t necessarily figure that you will able to fit the exercise into your routine either.