This Full-Body Knee Exercise Can Target Belly Fat Faster Than Crunches

A strong core does more than help you look good. You need to keep your core strong for balance, stability, and everyday movement. Whether you're playing sports or just walking up the stairs, your core helps keep you steady and safe. Strengthening these muscles can ease back pain, improve posture, support strength training, and even make breathing easier. (Here's how often you need to exercise your core for optimum results.)

Crunches may seem like the go-to move for a strong core, but doing hundreds of them won't give you a complete core workout, let alone get rid of belly fat. That's because your core includes more than just your abs. A strong core also involves strengthening your back, glutes, and pelvic floor. And if your goal is to shed belly fat, you need to boost your heart rate and burn calories.

That's where high knees come in. This dynamic exercise works your entire body and gets your heart pumping fast, especially when used in a high-intensity interval training (HIIT) routine. Just a few rounds of high-knees can torch calories and build functional core strength. That's what makes them a smarter choice than crunches if your goal is visible abs and a healthier core.

You may not notice which muscles you're working when doing high knees at a fast pace, so let's break it down. If you stand tall and raise one knee as high as possible, you'll feel just how many muscles this move activates. To lift your leg, the muscles at the front of your hip engage while your glutes extend. Your standing leg works to stabilize your body, recruiting your core, quads, and calves.

When you quickly switch legs, that small hop to shift your weight engages your lower abs and pelvic floor. At the same time, your obliques, transverse abdominis (the deep stabilizing muscle in your core), and back muscles help maintain your posture. You might also pump your arms to generate momentum, which activates your biceps.

Performed at speed, high knees mimic running in place, aside from the exaggerated knee lift. These quick bursts raise your heart rate fast, and you'll likely find you can't do them for very long. That's what makes high knees a great fit for bodyweight HIIT workouts, which are often more effective at burning belly fat than longer, low-intensity routines.

In a 2009 study in Medicine & Science in Sports & Exercise, women with metabolic syndrome followed one of three programs for 16 weeks: no exercise, low-intensity exercise five days a week, or a mix of high- and low-intensity workouts. The women who included high-intensity sessions three times a week lost significantly more visceral fat than those who exercised at a low intensity alone.

You may remember doing high knees in gym class, but you probably didn't think much about form back then. While you don't necessarily need to change into gym shoes, avoid casual footwear that might slip. If you're looking to engage the small muscles in your feet, try going barefoot.

Start by standing tall with your feet a comfortable distance apart and your weight in the balls of your feet. To activate your core, imagine zipping up a tight pair of jeans — maintain that subtle lift in your core throughout the movement. Raise your right knee as high as you can while curling your left arm up. Your opposite arm helps drive the motion and acts as a counterbalance.

Next, hop off your left foot, swing your right arm for power, land your right foot, and raise your left knee high. Continue alternating feet — hopping and driving the opposite knee up — landing lightly each time. Once you've got the rhythm, pick up the pace while maintaining that "zipping" sensation in your core. Try syncing your breath with your movement for better control.

To turn it into a HIIT workout, aim for 30 seconds of high knees followed by 30 seconds of rest. Repeat for 15 to 20 minutes to help burn belly fat. High knees also make a great warm-up for other workouts, like running, or can be part of a full-body HIIT circuit alongside moves like burpees, push-ups, and jump squats.