Russian twists are an effective exercise to build strong abs without a gym. Here's how to do them correctly, according to a trainer.

• Russian twists are a popular ab exercise for working the oblique muscles on the sides of the body.
• But common mistakes, like going too fast or using too much weight, can make the exercise less effective.

Russian twists can help you build strong abs at home, and you don't need equipment to make them work.

Starting with bodyweight Russian twists can help you dial in your form and develop a strong, stable core, Miriam Fried, NYC-based personal trainer and founder of MF Strong, told Insider.

Fixing common mistakes, like over-rotating or using momentum, can make your workout more effective. Focus on slow, precise movement with good form, Fried said.

Keep your feet on the floor at first

The Russian twist starts from a seated position with your knees bent. Fried recommends starting with your feet planted on the floor in front of you so you can move with control. Lean your torso back to about 45 degrees, holding tension in your abs to stay stable.

"Focus on feeling your core," she said.

Then, hold your arms out in front with hands together, twist your torso through one side, being sure to rotate through the shoulder rather than just reaching your arms across.

Return to center and repeat on the other side.

As you get comfortable with the movement, you can increase the tension on your abs by lifting your feet up so your shins are parallel to the floor, maintaining the 45 degree angle of your torso.

Be sure that your hips stay square and as still as possible; tilting them back and forth as you twist defeats the purpose of the movement, since you're not forcing your core to work to stabilize.

Slow down the movement

The benefit of Russian twists compared to other ab exercises is that the rotational movement works the obliques, the ab muscles along the sides of your core.

To get the most out of the rotations, slow it down, Fried said. Speeding through the rotation means your abs aren't maintaining as much tension (which is the point of the exercise).

Slowing down can also prevent you from over-rotating, which Fried said is another common mistake.

Turn just far enough that you can feel the sides of your abs working, then return to center. If your lower back starts to twist or cave, you're going too far.

"Don't crunch your back," she said.

Wait before adding weights

Since the ab muscles are relatively small in size, your own bodyweight is often more than enough to work your core. Even a little bit of added resistance can really ramp up the challenge, and many people will grab a medicine ball, kettlebell, or other weight for Russian twists.

But you'll benefit more from the movement by doing it correctly without weights, rather than loading up and letting your form deteriorate, according to Fried.

Try unweighted Russian twists to nail the technique, she said. Then, if you want to increase the challenge, add weight gradually.