The plank is one of the best exercise choices for a quick workout anywhere from the hotel gym to the airport lounge. But the classic plank — in which you support your body on forearms, or hands, and toes — may not seem as challenging after a while.

With core strengthening exercises, more is not necessarily better; holding a plank for longer than 60 seconds is a great example of the law of diminishing returns. Plus, it gets kind of boring.

Instead, you can add variety to the plank through these five variations, which don’t require any special gym equipment. You’ll get the same benefits as the classic plank while giving your workout a fresh twist.

Planks can be done daily, unlike most exercises. However, you don’t have to do them every day in order to maintain a strong and stable core. If you work out three to four days a week, adding one of these plank variations to each of your workouts should be plenty.

Or for a quick and easy full body workout at the end of a long day, pick one of these plank variations to do with squats and push-ups in your hotel room.

Elevated Plank
For this version, keep hands on the ground, but put your feet (toes really) on a bed, an ottoman or a bench. Hold your plank for a count of ten. Then release the plank and come rest on your knees for a count of ten.

Repeat this for a total of 10 rounds.

Leg Lift Plank
This version can be done on forearms or hands. Assume the basic plank position and lift your right leg for one to two seconds. Keep your leg straight, making sure to lift from your glutes.

Return your toe to the ground, and do the same thing on the left side. Alternate sides for eight to 10 repetitions per side.

Forward and Back Plank
For this plank variation, you’ll want to have your forearms on the ground. Keeping your body straight, push yourself forward by using your toes. Then move your body backwards, pushing your heels toward the wall behind you.

Your body should move as though it’s gliding above the ground, moving only forward and back, not up and down. Repeat for 10 to 12 repetitions.

Alternating Plank Twist
This variation offers a double bonus, in that it includes side planks to give your oblique muscles a little extra attention. Start on hands and toes in straight-arm plank position. Lift your right hand off the ground and rotate to a side plank position on your left side.

Pause for one to two seconds before returning to straight-arm plank position with both hands on the ground. Lift your left hand off the ground and do the same side plank on your right side. Take care to keep your hips below shoulders in between rotations.

Alternate sides for 10 to 12 repetitions per side.

Plank Jack
Here is your new in-room cardio option. Think of this as a jumping jack in plank form. Start with your hands on the ground and on toes in a regular plank position. Jump, with your feet out wider than your shoulders like you would in a standing jumping jack, but maintaining your straight body plank position.

Then jump your feet back to their original position. Do this for 30 seconds.

This is a great way to finish a workout with both core strengthening and cardio intervals.