Russian Twists are a popular exercise that targets the core muscles, particularly the obliques. To perform a Russian Twist, follow these steps:

1. Start by sitting on the ground with your knees bent and your feet flat on the floor.
2. Lean back slightly, keeping your back straight and your core engaged.
3. Clasp your hands together in front of your chest.
4. Lift your feet off the ground, balancing on your sit bones.
5. Twist your torso to the right, bringing your clasped hands towards the right side of your body.
6. Pause briefly, then twist your torso to the left, bringing your hands towards the left side.
7. Continue alternating sides in a controlled manner.

Russian Twists can be modified or intensified in several ways:

• To increase the difficulty, hold a weight or medicine ball in your hands while performing the twists.
• You can also elevate your feet off the ground to engage the lower abs.
• For beginners, it's recommended to keep the feet on the ground and focus on mastering the twisting motion first.

This exercise primarily targets the obliques, but it also engages the rectus abdominis, transverse abdominis, and hip flexors. It helps improve core strength, stability, and rotational power.

Here are some additional resources for further reading:

1. ACE Fitness - Russian Twist
2. Healthline - Russian Twist: How to Do It and Benefits
3. Bodybuilding.com - Russian Twist

Remember to always consult with a qualified fitness professional before starting any new exercise program, especially if you have any pre-existing medical conditions or injuries.