Whilst high intensity interval training (HIIT training), has been around since 1970, it has made a remarkable resurgence to popularity over the past few years. The principle of HIIT is that you perform a number of different exercises at a high intensity with little rest. It is believed that this will dramatically increase fitness, reduce fat, and enhance your health in many other ways.
What is HIIT?
HIIT is a cardiac training regime that requires you to perform multiple different exercises in the same workout session. These exercises form the intervals, and each interval in HIIT is comprised of a period of strenuous activity followed by a period of moderate intensity exercise. A warm-up exercise is performed prior to commencing HIIT, and the training protocol is finished up with a cool-down exercise.
Based on this protocol, one interval of HIIT training could include sprinting for 30 seconds, followed by 1 minute of walking or light jogging. You're allowed up to 10 seconds rest before commencing the next interval. The exercises you choose are largely up to you, with the only requirement being that there is a combination of strenuous and moderate exercises.
Whilst there's a lot of variance in what is considered an appropriate length of time to complete the HIIT training session, the consensus here is to aim for about 7 to 12 minutes in total for the whole workout. HIIT training is meant to be short, and this makes it great for busy people who work long hours or don't have much motivation to work on their fitness.
Benefits of HIIT
HIIT is reported to have a number of benefits, including:
- It is incredibly efficient and easy to find the time to complete a HIIT workout.
- Improvements in endurance
- Increases insulin sensitivity
- Decreases the risk of cardiovascular disease
- Increases fat loss
- Reduces cholesterol
HIIT improves endurance
High intensity interval training improves endurance in much the same way that moderate exercise over a longer period of time does. The difference is that the results are achieved much quicker than is possible through a moderate exercise regime.
In trials where HIIT has been compared to moderate aerobic exercise for up to 8 weeks, results showed that HIIT training improved oxygen capacity more than moderate exercise. Increases to the mass of the heart were similar with both types of exercise regime, but HIIT increased the amount of blood that the heart could pump by 10 percent.
HIIT boosts insulin sensitivity
In studies examining the effect of HIIT on glucose tolerance and insulin sensitivity, it has been found that HIIT training can increase insulin sensitivity. The implications of this suggest that HIIT could be a means to prevent and control type 2 diabetes, which is caused by a decline in insulin sensitivity.
Type 2 diabetes is currently treated with drugs like metformin, that decrease glucose production in the liver. These drugs, combined with an aerobic exercise regime and careful meal planning are the only way to control the disease and prevent the side effects of uncontrolled diabetes. HIIT training may be superior to moderate aerobic exercise, leading to greater control of diabetes and a decrease in mortality.
HIIT increases fat loss
HIIT training is thought to burn more fat than moderate exercise. Whilst performing 10 minutes of HIIT doesn't burn off as much fat as an hour of light walking, HIIT training has the benefit of continued fat burning for a few hours after the training is concluded. This is not the case with moderate exercise, which will burn fat during the period of exercise but cease to do so after conclusion.
Another benefit of HIIT training is that it appears to increase the body's ability to burn fat. This means that not only can HIIT burn fat for a sustained period of time after the exercise has ended, but that the body gradually learns to use fat more efficiently to provide energy. This benefit of HIIT leads to greater proportions of fat burnt compared to stored glycogen when performing any exercise afterwards. In fact, 7 sessions of HIIT over two weeks might be all it takes to start to see this kind of effect according to the results of this study.
HIIT lowers the risk of heart disease
HIIT can lower the risk of heart disease, as can other aerobic exercises. The effect of HIIT training may be more pronounced however, with noticeable increases to cardiac output and a strengthening of the heart.
In conjunction with this, HIIT can reduce LDL cholesterol and increase beneficial HDL cholesterol, protecting you from artherosclerosis. In a society that is increasingly reliant on takeaway and processed foods full of saturated fat, this is important, and it can prevent the clogging of your arteries that happens when you have a few too many greasy burgers.
HIIT - sample workout
- Light stretching and calisthenics to warm up
- Sprinting (30 seconds) - Walking (1 minute)
- Stair climbing (1 minute) - Squats (2 minutes)
- Jumping jacks (1 minute) - Crunches (2 minutes)
- Pushups (30 seconds) - Light cycling (1 minute)
- Light stretching to cool down
Is HIIT safe?
Because HIIT training requires you to exercise at 90 percent of your maximum heart rate, HIIT isn't for everyone. If you suffer from heart disease, chronic obstructive pulmonary disease, or other chronic conditions that affect your ability to exercise, you'd be better off following a much lighter exercise program to avoid harming yourself. Additionally, anyone who isn't overly fit shouldn't attempt HIIT. HIIT training should only be undertaken by people who have acclimatised to a moderate exercise regime first.
As with any exercise regime, it's important to discuss HIIT with your doctor. It's best to have your heart and other systems looked over to make sure you are healthy enough to commit to HIIT training safely. Your doctor will be able to tailor an exercise program that matches your needs based on your own individual health. When approached like this, HIIT is very safe and you'll be able to attain all the benefits without causing yourself harm.