The primary movement is called the Prime mover or Agonist
Do you mean flexion and (abd)uction?? If so, the prime mover would be the deltoid muscle with many smaller muscles assisting. If you are in fact meaning flexion and adduction, the prime mover would be the pectoralis major and the latissimus dorsi with many smaller muscles assisting.
your rectus abdominis is the prime mover in a crunch exercise or spinal flexion
quadriceps
biceps brachii
The prime mover is a conceptual term from Aristotle's philosophy to describe an unmoved mover that initiates all motion in the universe. Therefore, nothing performs the same movement as the prime mover since it is considered the ultimate cause of all motion.
Muscles can be classified into agonist (prime mover) muscles that directly produce a desired movement, antagonist muscles that oppose the action of agonist muscles, and synergist muscles that assist the agonist muscles in performing a movement. Additionally, stabilizer muscles provide support and stability to joints during movement.
The prime mover of hip abduction is the gluteus medius muscle. It is responsible for moving the thigh away from the midline of the body.
Your mothers vajina bone
The muscle that is responsible for most of a movement is called a prime mover. It may also be called an agonist.
The atissimus obrsi abdominals is the prime mover in a sit up.
The prime mover muscles for a power clean workout are primarily the quadriceps, hamstrings, glutes, and lower back. Additionally, the shoulders, traps, and forearms are also heavily engaged during the movement to lift the weight explosively.