According to an American College of Sports Medicine survey, the new top fitness trends for 2014 are high-intensity interval training like P90X and Cross Fit, which involve shorts spurts of intense anaerobic exercises with lower-intensity periods of recovery.

P90X, also known as Power 90 Extreme, is a home exercise routine notorious for its intensity. It uses cross-training such as martial arts, yoga and weight training in addition to a diet plan. These types of high-intensity interval training are aimed mostly for people who are already fit and are looking for something more challenging. Workouts usually take less than 30 minutes to complete. These types of programs are popular due to the short time interval, but also have high injury rates.

In its eighth year of completing this survey, the American College of Sports Medicine asked over 3,800 fitness professionals working in clinical, commercial and corporate gyms what the top 20 fitness trends would be for the next year. They could choose out of 38 choices, and were made sure to understand the distinction between a fad and a trend. The survey defined a trend as “a general development or change in a situation or in the way that people are behaving.”

In 2013, popular fitness trends included mud runs and obstacle races like the Tough Mudder and Spartan Race, which include wall climbing, crawling through mud, and wading through ice cold water. Zumba, a form of dance workout, has been popular in recent years, as well as Pilates, spinning, and kickboxing. However, these workouts didn’t make the top 20 list for 2014.

However, Walt Thompson, the lead researcher and a professor of kinesiology and health at Georgia State University in Atlanta, warns of the potential risks of high-intensity interval training. “It could result in orthopedic injuries or cardiovascular complications for people who aren’t accustomed to this kind of exercise,” he told USA Today. “That’s the danger of them which is why I was surprised this came in as No. 1.” People with heart disease, arthritis or diabetes should first consult with their doctor before starting any high-intensity interval training, as they may be at more of a risk for an injury.

Dietician Nancy Clark told USA Today that high-intensity interval training won’t last very long as a top fitness trend. “If Zumba has moved off the charts — and that is fun — how long will high-intensity exercise hang on?” she said. “We’ll find out. Likely longer among Type A, time-pressed people who are dedicated to maintaining their health.”

Other trends that were ranked in the top 20 for 2014 include getting educated and experienced trainers, weight loss, personal training, group personal training, yoga, and fitness programs for older adults. The survey, however, didn’t take into account the types of exercises that people do on their own, such as walking. Walking is the most common type of physical activity people undertake.