Answer:
Plantaris: This long, thin muscle runs along the back of the leg, from the end of the thighbone down to the Achilles tendon. The plantaris muscle works in conjunction with the Achilles tendon to flex your ankle and knee. You use this muscle every time you stand on your tiptoes.
— https://www.healthline.com/health/plantar-flexion#:~:text=Plantaris%3A%20This%20long%2C%20thin%20muscle,you%20stand%20on%20your%20tiptoes.
