Watch Zac Efron and Alexandra Daddario Nail This Core-Crushing Baywatch Abs Workout

• Begin on your back with your legs straight and your arms extended overhead.
• Actively press your lower back into the floor and draw your belly button into your spine.
• Inhale to slowly lift your shoulders, arms, and legs off the floor. Keep your hands and heels as low to the ground as possible, while still pressing your lower back into the floor. Maintain tight abs and glutes. It's OK to bend your knees if straight legs are too challenging.
• Hold like this for five to 30 seconds to complete one rep.

Zac and Alexandra do a tough variation of this, holding a resistance band between them and alternating slow crunches from a hollow hold position. Try the basic hollow hold to start, then grab a partner for the extra challenge.