Mermaid with Twist
All plank variations are excellent for targeting the deep stabilizing muscles between your hips and your shoulders, but the mermaid with twist unilaterally isolates each shoulder, improves spinal mobility, and targets the obliques.
Start in a side plank, balancing on your hand or your forearm. Check your form to make sure your elbow or palm is directly under your shoulder, your hips are lifted, and your obliques are engaged. Reach your top arm to the sky, then exhale as you thread it under your body, simultaneously lifting your hips upward and twisting your chest toward the floor. Inhale to return to side plank, and continue until your form starts to falter.