What is the core strengthening yoga posture where arms and legs are held straight out and the torso forms a V shape?

The posture described in the question is known as Navasana, commonly referred to as Boat Pose. In this yoga position, the practitioner sits on the floor, leans back slightly, lifts the legs off the ground while keeping them straight, and extends the arms forward. This creates a V shape with the body, engaging the core muscles effectively.

Navasana is designed to strengthen the abdominal muscles, improve balance, and enhance overall core stability. It not only targets the rectus abdominis but also engages the obliques and hip flexors, making it a comprehensive core-strengthening exercise.

The other options provided do not fit the description of the posture. Warrior Pose focuses on lower body strength and stability with a wide stance and extended arms, Shavasana involves lying flat on the back for relaxation and meditation, and Runner's Lunge is a dynamic posture that stretches the hips and legs while lowering one leg into a lunge position. Hence, Navasana stands out as the correct choice for a core-strengthening posture that forms a V shape with the body.