The huge appeal of high-intensity interval training

Mary Kate Frerichs of Timonium during the boot camp at MAC Hunt Valley Express.
Mary Kate Frerichs of Timonium during the boot camp at MAC Hunt Valley Express. (Lloyd Fox, Baltimore Sun)

It's a small room, but it has plenty of potential, tucked away beyond the lines of traditional treadmills and weight machines at the Maryland Athletic Club Express in Hunt Valley.

The room is filled with some items you expect to see at any gym — a rowing machine, a weighted ball, a punching bag — and some you might not: thick battle ropes and TRX suspension straps hanging from the ceiling.


Each of the students in personal trainer Doug Bopst's boot camp class last week used one of these pieces of equipment for a minute-long interval. After a quick and nonstop movement — lifting heavy battle ropes, throwing boxing punches or pulling themselves up by the TRX straps — they took a 10-20 second break. Then they rotated to a new piece of equipment. Bopst, 26, counted down from five, gave the go-ahead, and the cycle continued.

Within a few minutes of starting the workout, all four students in the class were sweating and breathing hard. This is high-intensity interval training. Heavy on the intensity.


"It's hard for me to motivate myself, but when we leave, [Doug] will be like 'great job today!'" said HIITer Mary Kate Frerichs, 21, a University of Richmond student. "Him pushing us and motivating us is the biggest thing that keeps us coming back."

Frerichs attended Bopst's boot camp class along with three other young women: her sister Colleen, 19, who attends Dickinson College, and her cousins Maggie, 21, who goes to High Point University, and Grace Geary, 18, who attends Notre Dame Preparatory School. The majority of the boot camp is made up of high-intensity interval training, a popular workout trend among young people.

The American College of Sports Medicine Health & Fitness Journal released a survey, completed by more than 3,800 fitness professionals worldwide, in its November/December issue forecasting the top fitness trends of 2014. High-intensity interval training took the No. 1 spot, its first appearance on the list, now published for the eighth year. Other trends making the list are also related to HIIT: body weight training (No. 2), personal training (No. 6), group personal training (No. 9).

HIIT is broken into brief intervals of high-intensity motion followed by brief periods of rest, said Billy DeLorbe, a personal trainer at the MAC in Timonium. The activity can be any type of exercise — sprinting, pull-ups, squats, tire flipping — as long as the heart rate changes between the intervals of motion and rest. Classes usually run about 30 to 45 minutes (with rest), but some programs are performed in less than 30 minutes.

DeLorbe said the period of rest doesn't necessitate ceasing all movement, just something less intense — like sprinting for a quarter of a mile and then jogging for another.

Reese Ashe, a personal trainer at Federal Hill Fitness, said HIIT started to grow in popularity around two to three years ago, after CrossFit became a success and served as a catalyst for various HIIT-focused gyms.

"I think [HIIT] will get bigger," Ashe said. "More classes will be designed, and more specialty gyms will be popping up."

Ashe, whose boot camp class is the most popular class at Federal Hill Fitness, said the average age of people participating in his HIIT class ranges from 21 to 28.

Tiffany Bryant, an exercise specialist at Towson University's Wellness Center, said she sees a lot of young people drawn to high-intensity workouts such as boot camps and CrossFit. One reason for its appeal to a younger crowd, she said, is its efficiency. Young people "like to work hard and then move on," Bryant said. "It's a get-in-and-get-out kind of thing."

Bryant said HIIT is a much faster trend than those of the past.

"Past fitness trends were more cardio-based," she said. "Running for longer periods of time, or lifting lighter weights with more reps. Now it's more heavy lifting and burning way more calories in a short amount of time."

And DeLorbe said HIIT combines exercises the way past trends did not.

"A big difference is in the past, your cardio and strength were separate," he said. "Now your cardio and strength aspects are blended together."

Tabata, Bryant said, is a popular form of HIIT. Like other types of HIIT, Tabata is broken into intervals, but it has a set ratio of 2:1 of activity to rest and always includes eight rounds.

Bryant said Tabata can be done with almost any exercise, or some combination of exercises — pull-ups, push-ups, burpees — but is typically done using body weight exercises or very light-weight exercises.

Bopst said he sees young people excel in HIIT classes and that HIIT often appeals to young athletes and former athletes because of its similarity to many sports.

"A lot of them are training for sports or they've played sports, like soccer or football or anything like that," he said. HIIT "is a lot of sprinting and stopping. When you're playing football, you do a play, and you rest, and you do a play, and you rest. [The training] mimics a game."

Most HIIT takes place in group training sessions — itself another trend. Sharon Nevins, MAC's vice president of marketing at the MAC, said MAC's biggest January initiative is offering gym-goers small group memberships, taking advantage of the trend. Nevins described the classes as a "sort-of hybrid" between one-on-one training and group classes. MAC has more than 25 different classes a week, she said.

Among those classes are shockwave, a boot-camp style class, barre burn, a total body conditioning class, and yoga shred, a combination of yoga, cardio and plyometrics, which focuses on working muscles rapidly. Nevins said young people are attracted to group classes for a social atmosphere as well as the intense workout.

"They can do it with friends or they can meet new friends," she said. "You have that 'I'll meet you at class' buddy system and you also have that personalized attention from a trainer."

For the Frerichs and the Gearys, working out in a small group is not only a social experience but a way for them to keep each other accountable.

"It's definitely better to have other people around you," Grace Geary said. "You can see different workout styles of people and different things they can do that I think 'Oh, I need to do that too. We can do that together.' It's the comfort of knowing that someone else is there struggling with you."

DeLorbe said in addition to creating a fun social experience, group sessions motivate people.

"I think of it like positive peer pressure," he said. "People are getting more into that because they can compete against and with each other at the same time."

For Maggie Geary, it's a class that mixes it up, like HIIT boot camp, that makes her keep coming back to the gym. Though she usually works out on her own at the gym and only occasionally takes group classes, she enjoys a change of pace.

"When I work out on my own I'm in a routine and I always do the same things, but in a class it changes every time you come," she said. "It's nice to work parts of my body that I've never worked out before and to wake up the next morning really sore."


DeLorbe said HIIT classes keep everyone, including young people, coming back because they're too fun to feel like exercise.


"It's an energizing type of workout," he said. "You're constantly adapting to the environment around you. It keeps you guessing."

But HIIT, like any form of exercise, comes with some level of risk. DeLorbe said that the probability of getting injured in a HIIT class is the same as getting injured while playing a sport, and stressed the importance of working with a personal trainer when participating in HIIT.

Michael Higgins, chair of the kinesiology department at Towson University, said the most common injuries that occur from high-intensity workouts are overuse injuries, injuries that occur over time because of repetitive motions.

"Most likely you'll have injuries like muscle soreness, tendonitis and bursitis," Higgins said.

Higgins said it's important for people to learn the proper technique for an exercise before executing it.

"If you go too hard too fast, you're going to get sore," Higgins said. "You have to progress into the exercise."

Dustin Blackwell, personal training director for Brick Bodies and Lynne Brick's health clubs, said form is crucial in any workout, as it maximizes the effectiveness of the activity, but even more so with HIIT.

"People of all fitness levels are participating in these high-intensity activities, and it's more important for them to be aware of their form," Blackwell said. "For the trainer, they're in a much less controlled environment. There's not just one client to focus on — they have to be aware of the entire group."

During Bopst's class, he regularly stood in the middle of the room, glancing at each student as they executed their exercises. He spent personal time with each — boxing, adjusting form, voicing encouragement.

For the last few minutes of Bopst's boot camp class, the Gearys and the Frerichs got on individual mats and worked on their core muscles. Many crunches and leg lifts later, the workout was finished.

The women let out sighs of relief as Bopst commended them for a job well done. All of them were sweating and showing signs of exhaustion, but they gathered together to talk and laugh as they caught their breath.

Things will be different the next time they come to class.

But that's the way they like it.