OWhen your fitness instructor tells you the jackknife exercise (also known as the “V-up”), you to know You have problems. This abs-focused move requires full-body engagement and is a favorite in Pilates, yoga, HIIT, and weight training classes. Jackknives are also one of the most technically challenging core exercises. If you’re not sure you’ve reached A+ form yet, don’t worry.
“[Jackknives] a great move for your core, especially your lower abs and hip flexors,” says Nike Lead Trainer Traci Copeland, your jackknife guide for this week’s episode of Well + Good. The right way. The movement also challenges your upper body and back strength because you have to bring your core to meet your lower body, which is no small feat.
Ever heard of a jackknife? Here’s how it goes: Lie down and fully extend your arms above your head. Using your lower core, drive your tailbone under and, keeping your back as straight as possible, lift your legs and upper body off the floor, reaching your hands to your ankles so your body forms a V. (You can also keep your legs bent, if that’s more comfortable for you.) Next, bring your legs and upper body back down to hover just above the floor, making sure to keep your abs fully engaged. Return to your V-shape and continue repeating until you complete the necessary reps. Watch Copeland’s demonstration at each step to make sure you’re practicing proper form.
Sounds simple enough, but in practice it’s a bit tricky. Like any fitness move, the jackknife takes a lot of practice, and Copeland says people in her classes tend to make the same mistakes over and over again. First, people tend to arch their backs in this exercise, a common error in abdominal exercises that puts the lower back at risk.
And second, it’s really tempting to rely on momentum to execute your jackknife, but the magic of this move is actually in staying in control and holding on to the top, says Copeland. (Of course it’s way harder this way, but are you really surprised?)
Now that you know the ins and outs of the jackknife exercise, you’re ready to take the HIIT class by storm. Just keep your two clues in mind: the core is engaged! No momentum!
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