ExerciseNZ media release: 11th June 2019

High Intensity Interval Training (HIIT) has remained popular for its reported benefits to health since its arrival on the exercise scene a few years ago, and for those with time restrictions that make longer workouts unrealistic.

The simplest explanation of what HIIT is for the uninitiated is that is its repeated cycles of hard physical activity with active rest in between each bout of intense work. Its popularity is in part because HIIT has been shown to improve heart health, exercise levels, and reduce fat, while maintaining muscle mass or, in less
active individuals, increasing it.

University of Otago researchers have also recently discovered that high-intensity exercise can reduce or reverse the loss in heart function caused by type 2 diabetes. The study found that three months of HIIT improved heart function in adults with type 2 diabetes, without any change in medications or diet. The study subjects were middle aged adults, and had an 80 percent adherence rate to the programme - which was unexpected due to the heart impairment causing exercise to be more difficult for diabetes sufferers - showing that appropriate HIIT can be achievable.

More studies are showing these sort of benefits for a range of lifestyle conditions so it can be safely said that high intensity training should be considered as part of a regular programme of physical activity. However, it’s not a one size fits all solution, or a solution that should fully replace a current programme.

A study reported in the Journal of Sports Medicine and Physical Fitness showed that participants in HIIT workouts experience a greater risk of injury, especially knees and shoulders. The study pointed out the benefits of HIIT training on a range of exercise outcomes, but commented on the risk of a 'one size fits all' approach to many HIIT programmes that see participants working at a level they are not able to sustain safely. The authors of the study noted that workouts with inexperienced participants without supervision were one of the main causes for concern, recommending support and advice before embarking on a HIIT programme.

A 2018 study led by associate Professor Gottschall with Bryce Hastings (Head of Research at Les Mills) resulted in evidence that any more than 30 to 40 minutes of HIIT in a maximum training zone per week can reduce performance and potentially result in a greater risk of injury, and does not contribute to higher results. Too much HIIT can result in negative training effect. They recommended adding HIIT training in amongst a varied programme of varied exercise.

It’s probably time you investigated adding some form of HIIT training to your workout. Just make sure you get the right advice so you can experience the benefits, without any unintended side effects.