Trainer: Alexia Clark, personal trainer at Alexia Fitness in Scottsdale, Arizona.

Benefits: The plank jack and bicycle crunch are both great exercises for your core to begin with. But in this workout, Clark adds a miniband to make the moves even more effective. With the added resistance, you’ll hit your oft-neglected lateral glutes and hip flexors while hammering your core muscles.

This workout is only 5 minutes, but with no rest in between rounds, you’ll be putting your ab strength and endurance to the test.

Source: This 5-Minute Core Workout Will Make Your Abs Beg For Mercy