Could fewer reps give better results in HIIT training?

New U.K. research suggests that completing fewer repetitions during high-intensity interval training (HIIT) workouts may actually provide better fitness benefits than completing more reps.

Carried out by researchers from the University of Stirling, Scotland, the team looked at 38 sprint interval training (SIT) trials from 34 existing studies which investigated the health benefits of regularly completing repetitions of a special type of high-intensity cycle sprint known as 'supramaximal'.

Supramaximal requires specialized exercise bikes that enable users to work out to very high exercise intensities.

To look at the effect of the number of supramaximal sprints on fitness, fitness levels were assessed by measuring VO2max, which is the maximum amount of oxygen the body is capable of utilizing in one minute and one of the best indicators of future health and risk of premature death.

Although it has been assumed previously that performing more repetitions of high-intensity exercise will produce greater improvements in cardiorespiratory fitness, the team actually found the opposite, and that completing fewer repetitions of sprint intervals on the bike and therefore spending less time working out could actually lead to greater improvements in fitness.

In fact after performing just two maximal sprints, each additional sprint in a training session actually reduced the overall improvement in fitness by around five per cent on average.

Commenting on the results Dr. Niels Vollaard, Lecturer in Health and Exercise Science in the Faculty of Health Sciences and Sport, said, "Lack of time is frequently cited as one of the main barriers to people becoming or staying physically active. High-intensity workouts have begun to tackle this problem, allowing people to get maximum health benefits while working out for a shorter time."

"We found improved cardiorespiratory fitness does not suffer when people complete fewer sprint repetitions and that this may even produce better results. The optimal number of repetitions appears to be just two, so workouts based on supramaximal sprints can be kept very short without compromising on the results."

As the study looked only at supramaximal exercise, Dr. Vollaard added that "To encourage more people to become active and help increase the health of the population, we need to investigate the optimal duration and number of sprint intervals people could undertake on a bike, while getting the same benefits as longer sessions."

Dr. Vollaard also added that the team are now researching further to understand better the mechanisms behind the unexpected finding.

The findings can be found published online in the journal Medicine and Science in Sports and Exercise.