Planks and crunches are both exercises that target the core muscles, but they work these muscles in different ways.

Planks:

• Planks are an isometric exercise, meaning that the muscle is contracted but does not change in length.
• Planks are a full-body exercise that works the core, shoulders, and legs.
• Planks target the rectus abdominis (six-pack muscle), transverse abdominis (deep abdominal muscle) and the obliques (side abdominal muscle).
• Planks focus on stability and balance, which can help to improve posture and reduce the risk of back pain.
• Planks are typically performed in a prone position, with the body in a straight line from head to toe and the hands or elbows on the floor.

Crunches:

• Crunches are a dynamic exercise, meaning that the muscle changes in length during the movement.
• Crunches specifically target the rectus abdominis (abs)
• Crunches are performed in a seated or lying position, with the knees bent and the feet flat on the floor.
• The movement of the crunch involves lifting the upper body towards the knees using the abdominal muscles.

In summary, planks are a full-body exercise that focus on stability and balance while crunches are an exercise that specifically target the rectus abdominis muscle, and are focused on the movement of the upper body towards the knees. Both exercises are effective for strengthening the core muscles, but planks may be a better choice for those looking to improve overall stability, while crunches may be better for targeting the abdominal muscles.