High-intensity interval training (HIIT)—which involves short bursts of high-speed, high-power exercise with brief breaks between sets—ranks among the top three fitness trends of 2019, according to the American College of Sports Medicine. HIIT workouts often include both cardio and strength training. Think sprints and fast-paced squats, lunges, pushups and dumbbell lifts. “It’s all about doing things more quickly and with more weight,” says Cindy Bailey, PT, DPT, OCS, SCS, ATC, director of Physical and Occupational Therapy at the Orthopaedic Hemophilia Treatment Center of the Orthopaedic Institute for Children in Los Angeles. Popular exercise programs that incorporate HIIT include CrossFit, Orangetheory Fitness, many boot camp workouts and F45. Here’s what you need to know before you jump on the bandwagon.
Are there benefits to HIIT?
These workouts boost your heart rate and burn fat in a short amount of time. A 2016 study found that one minute of pushing yourself to the max on a stationary bike had the same impact on aerobic fitness, muscle function and blood-sugar control as 45 minutes of moderate pedaling. Most of the research has focused on the cardiovascular benefits of HIIT. However, a 2018 study suggested that intense 20-minute weight training sessions improved muscle fitness just as much, if not more, than 45 minutes of traditional lifting.
What are the risks?
To exercise safely, you must do it correctly. Lifting weights the wrong way, for example, increases the risk of strains, sprains, tendon ruptures and bleeds. And, says Bailey, the faster the workout, the harder it is to maintain proper form. “People get carried away with how fast and how intense they can make their workout rather than focusing on the form of the specific exercise,” says Bailey. The National Hemophilia Foundation’s (NHF) guide to exercise, Playing It Safe, considers intense workout programs like CrossFit to be moderate to high risk.
Am I ready for HIIT?
HIIT is rigorous so you need to be in good physical condition before you try it, says Bailey. Can you do a 35-to-45-minute cardio workout that has you sweating and breathing heavily? Can you lift light weights without injury and feel good the next day? Bailey says you need to answer yes to both of these questions before trying HIIT. If you answered no to either, your physical therapist can help you design an exercise program to prepare you for HIIT. If you’re new to exercise, do at least 12 weeks of cardio and resistance training before starting HIIT.
How can I do HIIT safely?
First, talk with your PT, who can determine what exercise modifications you may need to make. For example, elbow or shoulder problems may require you to stay off the pullup bar. You may also need to avoid high-impact exercises like box jumps. Pick an instructor willing to work with your PT on the most appropriate HIIT workout for you. Practice the exercises slowly at first and then gradually pick up the pace after you’ve mastered the form. It will be worth the effort. “It’s a wonderful workout if you’re in the shape to do it,” says Bailey.