Let’s start with the basics, how do you scientifically define what HIIT is?
High-Intensity Interval Training (HIIT) is defined as exercise that spikes your heart rate above 85 percent for two thirds of the total duration. Typically, 30 minutes is the maximum amount of time that individuals can perform HIIT with quality.
So, there are a lot of things that are positioned as HIIT but aren’t necessarily meeting the scientific definition of HIIT? How can we be confident that certain training is actually going to deliver the transformative effects of HIIT?
It comes down to the specific moves and how they are structured, which is where the testing comes in. The unique thing about LES MILLS GRIT workouts is that they are tested and refined, so you can be confident that the sequence of exercises and specific durations will deliver the results you are hoping for.
Can you explain a little about what’s involved in testing each LES MILLS GRIT release?
There are new LES MILLS GRIT workouts created every three months. Les Mills Jnr, Corey Baird and Erin Maw are the creative team who shape the draft format and select the music for each release, and then it’s sent to me for testing.
Firstly, I trial the workouts with three to four LES MILLS GRIT experts – these are individuals who have been training with LES MILLS GRIT for over five years. After these initial sessions, I am more familiar with the workout and how to coach it, so then I trial each format separately with 20 to 40 people ranging in age from 20 to 55 years and varying abilities. During these sessions I collect heart rate data to calculate the amount of time each individual is performing in the different zones, more specifically 85-100 percent heart rate max zone. This data is shared with Bryce Hastings, Les Mills Head of Research, who evaluates the results. Then, together with the creative team, we refine the workout to ensure it drives heart rates into the maximum training zone for the optimal durations.
If there is a novel exercise with potential risk, I also perform ground reaction force tests to ensure repeated movements are safe for the joints.
If you’re not getting the intensity right, how do you adjust the workout to ensure it’s hitting those peaks?
Typically, we modify or replace a particular exercise, but we can also adjust interval times or the order of tracks. In the last six years we have learned a ton about how to develop the ultimate 30-minute HIIT session! For instance, we know longer intervals at the beginning of the session are key, and it’s ideal to have a specific ratio of lower/upper body exercises.