HIIT Was Named The Most Popular Workout 2 Years In A Row. Here's Why It's Not Going Anywhere

HIIT isn't just a timesaver: It also works. "From the heart to the muscles to the metabolic system, all are pushed to the limit, and the body’s response is to function more efficiently," explains Kaiser Permanente's Robert Sallis, M.D.

According to HIIT expert and 12-Minute Athlete founder Krista Stryker, HIIT isn't just great for the person who's too busy to work out. "It's time-efficient, but it also works well as an equipment-free workout, so you can still do HIIT no matter where you are, whether it's outside in a park, your tiny apartment, or a hotel room," she explains. "Plus, it gets results—even just a few HIIT sessions a week will get you stronger, leaner, and in better shape than if you spent double or triple the amount of time doing steady-state cardio."

"That being said, I advocate the yin/yang philosophy with fitness and life," he adds. "You maybe going hard with your HIIT workouts every day and loving it, but if you are serious about being the best you, it’s critical to understand balance. Mix in a yoga flow a few times a week to complement your kick-ass HIIT workouts."

Want to get your HIIT game on ASAP? If you don't want to be bothered with equipment, give Stryker's leg-focused workout below a try—and don't worry if you don't have access to a sunny beach. You can do these in your apartment!

Start in a kneeling position while pulling your shoulders back and bracing your core. Sit back slightly, then thrust your hips as you jump your legs up so that the bottom of your feet are on the ground and your body is in a deep squat position. Immediately do a tuck jump, bringing your knees toward your chest, then step down to the starting kneeling position and repeat.

Start in a squat position with one hand touching the ground. Jump up as high as you can, rotating 180 degrees midair. Land back in a squat position, touching the ground with the opposite hand. Repeat.

Start in a lunge position with your knees touching or almost touching the floor. Without pausing, alternate legs, bringing your opposite leg forward into a lunge position. Continue alternating legs while moving forward.

From standing, squat down and jump as far forward as you can, explosively. Repeat, trying not to pause in between jumps.

Want more workout ideas? Try McCullough's ab exercises.