keymuscle
nounUK /ˈkiːmʌsəl/
US /ˈkiːmʌsəl/
A keymuscle is a muscle that is very important for a movement.
The heart is a keymuscle that pumps blood around the body.
OTHER MEANINGS
2. A muscle that is central to a skill or sport.
Strong legs are a keymuscle for running fast.
3. A person who is very important to a team or group.
She is the keymuscle of our project team.
4. The most important part of a machine or system.
The engine is the keymuscle of the car.