Such training, known as HIIT, typically involves short bursts of high-intensity exercise followed by a short period of rest or recovery: intermittently sprinting for 30 seconds, for example, during a moderate-pace jog.
HIIT is a worthy way to meet your physical activity guidelines, he said. "But there's a word of caution with that: Anytime you do high-intensity anything, there may be an increased risk of injury."
If you doubt your ability to safely exercise in high-intensity bursts, Thompson recommends that you "get a good physical exam" before starting a program.
This year's survey, which included responses from 4,133 fitness professionals around the globe, placed "group training" -- classes involving more than five participants -- in the No. 2 slot. Meanwhile, "wearable technology" -- such as activity trackers and smartwatches -- came in third, and "body weight training" -- the use of your own body weight as a form of resistance while doing modified pushups and other exercises -- came in fourth. "Strength training," or the use of barbells and weights, placed fifth.
Thompson said the survey was developed for two purposes, the first being "to help guide the fitness industry."
Although most of the industry is "commercial properties," the survey is also helpful to community-based organizations, corporate wellness programs and medical fitness centers.
"They need some direction as to what will be the next trend in the industry so that when they use their valuable resources for something, they know it's going to work," Thompson said.
"We also do it from the perspective of people who use the gym, the clients," he said. "It helps them identify gyms across the country that are offering the best kinds of exercise programs."
Three new trends found a place on the top 20 list: "licensure for fitness professionals", "core training" and "sport-specific Ttaining." Licensure refers to the general trend toward more regulation of fitness professionals, such as personal trainers. Core work stresses strength and conditioning of the stabilizing muscles of the abdomen, thorax and back. Sport-specific exercising is usually geared toward younger athletes and focuses on a single sport, such as tennis or boxing.
Meanwhile, "work-site health promotion" (which ranked 16th in last year's survey) and "outcomes measures" (previously 18th) fell from the top 20 list. In other words, incentive programs in employer-based health care benefits plans and comparison measurements to improve performance are no longer fashionable among the gym set.
One of the biggest surprises on the 2018 list was the "re-emergence of group exercise programs," said Thompson, who remembers "back in the day when that was all we did."
Personal training, which was introduced around 2000, reduced the popularity of group training, he noted. However, after the recession, less expensive group training sessions re-emerged and apparently continue to thrive. "It's got to help increase revenue and decrease expenses," Thompson said.
Another trend for 2018 will be older adults being welcomed back into fitness clubs.
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Most gyms "still see their greatest revenue source as the 25- to 35-year-old age bracket," Thompson said. But the "really smart clubs" are changing music and lighting during slower times when the typical gym-goer is at work, "so that now, the 60-year-old feels comfortable going into the gym," he said. "It makes total sense."
Finally, yoga remains in the top