I'm sure many of you will agree, trying to fit exercise into our already packed daily lives can feel like a challenge. But did you know that just 15 minutes of a high-intensity workout could be just as beneficial as an hour's worth of cardio?
High-intensity Interval Training (HIIT) involves repeated bursts of intense workouts that are each followed by active recovery periods. Research has shown that HIIT triggers the same changes you may expect with endurance training such as increases in exercise tolerance, metabolism and fat burning.
The intense nature of exercise means that the duration of the workout needn't be very long. A study found that after six weeks of training, those who completed 4-6 intervals of 30-second sprints three times a week lost more body fat than those who did 30-60 minutes of steady-state cardio on an inclined treadmill – ideal for those with a busy schedule!
There are so many different and exciting workouts you can do and the great thing is that training can be done anywhere without the need for equipment – the basic concept of exercising for short periods with maximal effort means you can adapt it to any time, financial and space constraints you have.
However, it's not just the practicality that's mind-blowing, there's also the after effect. High-intensity training can stimulate your human growth hormone (HGH) by up to a whopping 450% during the 24 hours post-workout. HGH is responsible for increased calorific burn and has been argued to also slow down the ageing process – prepare to feel younger and look younger too!
Working your body close to its VO2 max during exercise triggers what is known as the 'afterburn effect'. Your body continues to consume oxygen up to 48 hours after exercise and it takes approximately five calories to consume one litre of oxygen, so the increased oxygen intake means more calories burned.
Most sessions last around 15-30 minutes and have a 2:1 ratio for rest to exercise. One of the most simple yet effective example of this is 60 seconds walking/jogging followed by a 30 second all out sprint – repeat this several times.
One of the most popular methods, 'Tabata' training, has a 1:2 rest to exercise ratio which includes repeated sets of 20 seconds work and 10 seconds rest and typically lasts around 5-10 minutes. An example of a total body workout includes:
With any form of exercise, there is always the risk of injury. HIIT is a powerful form of training, so try not to push yourself too much every day. Overtraining doesn't produce optimum results, instead it can lead to symptoms such as chronic fatigue, colds and viruses and muscle damage. There are also risks to the immune system and Central Nervous System (CNS) through excessive high-intensity exercise.
HIIT is recommended to those with a reasonable level of fitness without cardiovascular issues. To ease yourself into this type of exercise, you can shorten your exercise time, lengthen your resting period – or even both if that helps! Try to do this once or twice a week, adding in extra sessions once you build up your aerobic and anaerobic capacity – try sticking to a maximum of four- five sessions per week to allow your body sufficient recovery time and prevent injury.
A great example of a HIIT programme that you can follow at home is the very well known and popular Insanity Fitness workouts – these target cardio, power and resistance through maximal effort exercises that take no time at all to do and really get your body working.
Just think, the time it took you to read this, you could have completed a quick session!
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Nutritionist Emma Brown (ANutr), MSc Human Nutrition is passionate about how food science applies to the human body, and how the nutrients in what we eat affect us and ultimately have an impact on our health.