The fitness trend of HIIT (high-intensity interval training) and studies that support its benefits are being questioned by Department of Kinesiology Chairperson Paddy Ekkekakis and other scholars through a series of six papers. As defined by Harvard University’s School of Public Health, HIIT is a type of interval training where short bursts of high-intensity movements alternate with brief periods of lower-intensity movements to elevate the heart rate to 80% of one’s maximum potential.
The articles — five of which have been published to date by Elsevier and Human Kinetics journals — are titled “Extraordinary Claims in the Literature on High-Intensity Interval Training,” and examine not only claims made by media, literature and research, but foundational issues in the field of kinesiology, which has resulted in a HIIT frenzy around the globe. Ekkekakis is the lead author on all six papers, the last of which is in the final round of peer review.
A summary of the articles
The first article examines the quality of evidence supporting the argument for HIIT. The most extensively studied outcome — an improvement in aerobic capacity, which is how well the body uses oxygen to keep going during activities that require sustained effort — has been studied in samples that are far too small to carry any validity, according to Ekkekakis and statistical experts.
The second paper of the series highlights false claims made by media about HIIT — or as Ekkekakis puts it, their “spin on research.” Headlines promoting how HIIT can lead to longevity or cut mortality risk in mere moments each day can be common in the media. Specifically, Ekkekakis cites examples where reporters have portrayed research findings to the public in a misleading way by misinterpreting research.
In the third paper, Ekkekakis and colleagues from the United States and Canada reviewed evidence contradicting several arguments for HIIT. For instance, the belief that the primary reason for physical inactivity is the absence of free time or that a significant proportion of adults are drawn to the idea of high-intensity exercise. HIIT is often perceived as an ideal solution by individuals who do not regularly engage in physical activity because they believe it takes only a few minutes of exercise each day to lose weight, but this is not entirely accurate.
An emphasis is placed on the absence of interdisciplinary communication and collaboration. “The lack of interdisciplinarity is an existential problem or threat to the field of kinesiology,” said Ekkekakis. For example, a psychologist may find different findings in the same research done by an exercise physiologist, but both findings must be considered when making conclusions.
According to Ekkekakis, the argument for HIIT and its supporting research began in the field of exercise physiology and was brought to the domain of public health without collaboration from other health disciplines.
In the fourth paper, Ekkekakis examines the sustainability of high-intensity interval training as a form of exercise by reviewing eight randomized controlled trials that compared it to moderate-intensity continuous exercise. The findings indicate most of the individuals assigned to HIIT either reduced their exercise intensity or quit the program altogether when left unsupervised.
The last two papers in the series examine how HIIT makes people feel. According to Ekkekakis, claims that HIIT is an enjoyable or pleasant form of exercise go against decades of research. “There’s a level of intensity [of exercise] and if you exceed that level of intensity, inevitably, everybody starts feeling worse.”
Less is more? Think twice
Fascination with messages that seem to question or defy conventional wisdom is a well-studied phenomenon in psychology, according to Ekkekakis, and especially prevalent in fitness, where many people want to believe that they can reap more health or fitness benefits with less time and effort.
“These types of messages have been used by politicians and religious leaders,” he said. “They capture your attention, and you want to believe them, especially when the message is, ‘forget 150 minutes of exercise, you just need to do one.’”
In summary, Ekkekakis recommends being skeptical of claims that seem “too good to be true” and appear to question or undercut the credibility of any heavily researched discipline.