How do staggered myotomes help a lancelet swim?

In lancelets, the main body musculature is organized into horizontal, chevron-shaped blocks known as myotomes. This specific arrangement allows the muscles to pull more effectively, facilitating the side-to-side, undulating movement of the body required for swimming.1

While the myotomes provide the power for locomotion, the notochord plays a critical supporting role by maintaining the body's length and preventing it from shortening during these swimming motions. This segmental organization of muscles is a characteristic shared with vertebrates, and it is believed to provide more effective body coordination during movement.123