Les Mills: Which HIIT workout could make you 20 years younger? 

The workout uses the transformative high-intensity interval training formula, where small volumes of exercise are used to stimulate disproportionate increases in cardiometabolic health. Participants used a stationary cycle to pedal through six 30-second sprints (at 40 percent of their peak power output) interspersed with three-minutes of active recovery. This short, but sharp 20-minute workout was performed every five days for six weeks – amounting to nine workouts in total.

“This formula is highly effective, but not entirely revolutionary,” explains Dr. Jinger Gottschall, science adviser for the American Council on Exercise (ACE). “Workouts such as Les Mills SPRINT® follow a similar format, using intense bursts of powerful pedaling followed by periods of recovery – with the work durations often lasting between 20 and 40 seconds.”

Initially, the researchers recruited 19 masters athletes, aged 55-74. These life-long exercisers were competitors in cycling, rowing, squash and triathlon events. Associate Professor, Peter Herbert, himself a 76-year-old masters athlete, persuaded the cohort of men to replace their intense weekly training sessions (typically three per week) with just one HIIT cycle session every five days. The participants were understandably reluctant, as they anticipated a steep decline in fitness.

However, six weeks into the study, they were pleasantly surprised. Despite doing nothing but a HIIT cycle session every five days, and no more than 30 minutes of gentle walking or jogging a day, they saw remarkable changes.

There were significant improvements in leg power, aerobic capacity and body fat – not to mention enhancements to their age-related physiological profile.

Interested in finding out whether the effects could be long-lasting, four years later the researchers retested the same men. During the earlier testing, they had an average age of 64 and a VO₂ max of 38ml/kg and a VO₂ max of 38ml/kg (VO₂ max is the maximum (max) rate (V) of oxygen (O₂) your body is able to use during exercise), which is considered excellent for their age – and on par with a non-athletic male aged 45-49 years old. After the six-week HIIT cycle regime, and the following four years of doing their own thing (many continued doing HIIT cycle workouts once every five to ten days), their VO₂ max improved to 44ml / kg – with their average age now at 68 this meant most had the cardiovascular health of someone 20 years younger!

The high-intensity interval cycling workout, Les Mills SPRINT®, which uses the same principles as the cycle sessions used in the study, has been shown to significantly improve cardiovascular, metabolic and musculoskeletal fitness. In six weeks, a group of fit adults reduced body fat mass and blood pressure, while enhancing their cardiovascular fitness, lean body mass, glucose tolerance and strength – simply by replacing one 60-minute cardiovascular training session with two 30-minute LES MILLS SPRINT workouts.

"We've long known that high-intensity exercise can make a significant difference in overall health and fitness in a relatively short amount of time. But because this type of exercise often involves weight-bearing impact, it hasn’t been a viable option for those who suffer foot, knee, and lower back pain," says Dr. Jinger Gottschall, lead researcher of the study. “This highlights how low-impact, high-intensity interval cycling can achieve similar results to weight-bearing HIIT. There is no complex technique to master and you manage your own resistance. It allows you to safely push your body through high-intensity intervals and swiftly amplify your fitness level.”

Written by Emma Hogan, content creator and copywriter for Les Mills.