Try These Core exercises for your obliques instead of russian twists
Side Plank Variations
- Side plank same knee/elbow crunch. 
- Side plank with hip abductions. 
- Form - draw your belly button in towards your spine and push your body away from the ground, especially in the shoulder; Maintain head, shoulders, hips and feet in alignment. 
Side V Up
- Legs straight, Arm straight . 
- Longer lever therefore harder. 
- Modification: side crunch with knees bent. 
- Draw belly button in towards your spine throughout exercise. 
