There’s plenty to be said for fancy gym equipment, but one of the best tools you can keep in your workout arsenal is basically a giant rubber band.

Resistance bands are rad because they can help you take bodyweight exercises to the next level. And with bands that range from easily stretchable to super tight, the exercise variations are endless.

That’s one of the reasons personal trainer Massy Arias swears by them. “Resistance training can be very effective and relatively simple to follow — not to mention mobile,” she says. “Bands are so easy to keep at home or pack for a quick workout anywhere.”

1. Standing knee tuck

Stand with feet slightly wider than hip-width apart and place the resistance band around the middle of your feet.

Lift your left knee toward your chest and crunch your right elbow toward left knee. Try to touch knee to elbow without rounding your shoulders. Return to starting position and repeat on the other side. Continue alternating.

2. Hollow body roll

Lie faceup, arms extended straight overhead with the resistance band looped around your wrists. Hover your shoulders and legs off the floor for a hollow hold.

Next, use your core to roll your body to the right, keeping arms extended, biceps next to ears. When you reach starting position, roll back to the left. That’s 1 rep.

3. Bicycle crunch

Start in a seated position with the resistance band looped around your feet, knees bent, heels resting on the floor.

Lean back to about 45 degrees until your core engages and lightly touch fingertips to the back of your ears. Use your core to rotate at the waist, bringing your right elbow to left knee as the right leg straightens.

Then, twist your torso to bring the left elbow to the right knee as the left leg straightens for 1 rep. Continue to alternate.

4. Side plank

Start in a high plank position with the resistance band looped around your ankles. Shift weight to the right hand, stacking feet, placing your left hand on hip.

Lift the left foot off the right foot until your feet are hip-width apart and hold for 30 seconds, or as long as possible. Return to starting position and repeat on the other side.

5. Single-leg T row

Stand with your feet hip-width apart and loop the resistance band around your right foot while holding the other end in your left hand. Shift weight onto your right leg, then hinge at the hips and lean forward, extending your left leg behind you.

When your chest is parallel to the floor, pull the resistance band toward you by sending the left elbow straight back and keeping it close to your side. Extend arm, then return to starting position. Complete reps, then repeat on the other side.

6. Spiderman push-up

Start in a high plank position with the resistance band around your feet, wrists directly under shoulders, and core engaged. Lower your chest for a push-up as you draw the right knee to touch the right elbow. Push back up to starting position, then repeat on the other side for 1 rep.

7. T rotation lunge

Start standing with arms extended straight in front of you. Hold the resistance band shoulder-width apart. Step your right foot back into a lunge, lowering until your thigh is parallel to the floor.

Use your core to rotate torso to the right, pulling the resistance band as wide as possible. Drive through your right heel to return to starting position. Complete reps, then repeat on the other side.

8. Unilateral squat

Stand with feet slightly wider than hip-width apart, toes pointing forward, and loop the resistance band under the ball of your left foot and around left wrist.

Extend arms straight in front of you, and send hips back to lower into a squat, keeping your chest lifted. Return to starting position. Complete reps, then repeat on the other side.

Arias particularly likes utilizing resistance bands to build strength in the core, an area she’s been more focused on since becoming a mom. Moves like the resistance band exercises below, she says, can help you do the same.

“Anything you can do to prepare your body for that experience is key,” she explains. “Maintaining a level of fitness before and during [pregnancy] is important so your body can support the changes, like a belly. After the birth, listen to your body and do what’s best for you.”

Here, Arias pulls together nine resistance band exercises that target the muscles of your core. “All of these moves really challenge your obliques and the entire abdominal wall,” she explains.

And while the midsection is the focus, you’ll challenge your upper body and lower body as well, making these moves the perfect addition to your strength routine.

For a quick, core-strengthening workout, Arias recommends this 4-move routine. Complete 3 sets of each exercise in order. Perform each exercise for 8 to 10 reps and rest for 30 seconds in between each set.