You’ve probably heard of high-intensity interval training, or ‘HIIT’ for short. 

It’s become widely popularised among both elite athletes and amateur fitness enthusiasts due to its reported ability to bring about positive health outcomes in a relatively short session and time period.

When I say ‘positive health outcomes’, I mean improved VO2 max (which represents the maximum amount of oxygen the body can use to metabolise energy and is considered the gold standard for prognosis of morbidity and mortality), reduced blood sugar levels and body fat percentage.

However, questions have been raised by experts as to whether the high-intensity part of the exercise may increase risk of adverse events in more vulnerable individuals, such as those over 65, or with a clinical diagnosis.

Our team has spent time reviewing studies to quantify these reports and give you our take.

There have been over 15 studies of varying quality that have looked at interval training in over 65s, including a new study by a group in France (Bouaziz et al, 2020), who set out to investigate whether the research indicates HIIT being safe and/or effective for those over 65. For context, most HIIT exercise was found to be prescribed at a heart rate of between 85% and 95% of Heart Rate max (HR max).

Top tip: The easiest way you can calculate your HR max is by subtracting your age in years from 220.

Here’s what they found:

The French study found that aerobic endurance training – i.e. steady-state heart rate exercise (not HIIT) – has a significant improvement in cardiovascular fitness (particularly VO2 max). This complements the already strong and compelling evidence base on the benefits of aerobic exercise.

But more interesting, the study found that the research base on HIIT exercise showed the method was very safe for those over 65 with no significant adverse events across the subjects. In fact, the HIIT groups found their fitness improved to a greater extent than that of the traditional aerobic endurance training. On average the HIIT group had a higher VO2 after the trials by 4.61 ml/kg/min.

And when you consider that for every 3.5 ml/kg/min increase, there’s known to be around a 15% reduction in cardiovascular disease risk, these findings are significant.

But here’s the downside:

HIIT is more difficult to complete and, although it takes less time, it can be uncomfortable and unenjoyable exercise to do.

These studies also only investigated individuals with stable blood pressure and heart rate rhythms, so there’s definitely further investigation to be done. 

However, it provides another option for older adults to improve their fitness and with the help of our CPET, we can accurately prescribe bespoke exercises for you.

The CP+R insight:

In addition to beavering over these reports, we’ve also been running our own study on HIIT vs aerobic endurance training over the past year, and were pleased to present our findings at a number of scientific conferences earlier in the year.

We were investigating whether HIIT training was safe for individuals with mild to moderate cardiovascular risk and found that it was overwhelmingly positive ,and had some powerful long term positive impact on our clients’ outcomes.

We’re currently working closely with the University of Exeter to explore a more in-depth and high powered study to add further to the literature – so watch this space!