Remember the buzzy boutique fitness classes that soared in the mid to late-2010s? There was a time when you couldn\u2019t skim a stone down 23rd Street in Manhattan without it ricocheting off three different studios, each offering their unique spin on high-intensity interval training, or HIIT.<\/p>\n
I pretty much lived in those studios, hitting three or four classes a week\u2014oftentimes more. But now? Those classes just feel like, well, a lot. Honestly, I get tired just thinking about it. And it turns out, I\u2019m not the only one.<\/p>\n
According to a 2025 report from the Sports and Fitness Industry Association, participation in high-intensity interval training (HIIT) and bootcamp-style workout classes has been slipping since 2019, while functional fitness<\/a> and low-impact workouts like Pilates<\/a> and yoga<\/a> have been gaining ground.<\/p>\n \u201cYou\u2019re definitely hearing it and seeing it, along with the rise of strength and Pilates,\u201d says Sam Tooley<\/a>, a performance coach and the co-founder and CEO of group fitness studio Alpha Fit Club<\/a>. \u201cI think they\u2019ve given what appears to be the same customer base that would have attended HIIT classes, which were way more prominent, a different alternative that is resonating.\u201d<\/p>\n While it\u2019s normal for fitness trends to come and go, industry experts think there\u2019s something else going on when it comes to the drop-off of interest in HIIT workout classes.<\/p>\n \u201cHIIT sessions tax both our aerobic and anaerobic capacity, while also putting a significant physical load on multiple muscle groups at the same time,\u201d says Jesse Shaw, DO, USAW<\/a>, sports medicine physician and associate professor of sports medicine at the University of Western States. \u201cDue to the unique stress and the often heavy and intense movement required, people burn themselves out.\u201d<\/p>\n But there\u2019s nothing inherently wrong or unsustainable about HIIT workouts<\/a>. In fact, with benefits to V02 max<\/a>, cardiovascular health, and overall athletic performance, it\u2019s one of the more valuable components of any well-rounded fitness regimen. So we talked to the experts to find out why people are losing interest, and how you can take advantage of everything these workouts have to offer\u2014without burning out.<\/p>\n Make sure your \u2018HIIT class\u2019 is actually a HIIT class<\/p>\n Turns out, that boutique studio workout you\u2019ve come to know as HIIT might not be HIIT at all, but rather a watered-down, less effective version that\u2019s probably putting unnecessary strain on your body.<\/p>\n \u201cWhat most workout classes are calling HIIT is not really HIIT,\u201d says Danny King, director of performance and recovery at Life Time<\/a>. \u201cHigh-intensity interval training, in scientific terms, is short-duration, high-intensity intervals\u2014with long rest periods,\u201d the latter being a key component,\u201d he says. \u201cIf you aren\u2019t resting enough, the intensity drops, not allowing a person to push hard enough to create the stimulus we are looking for.\u201d In many popular workout classes that advertise themselves as HIIT, rest periods are typically between 30\u201360 seconds long, with work periods sometimes lasting more than twice that.<\/p>\n