There are several: to name the main ones it would be: quadratus femoris, gemellus superior, gemellus inferior, obturator internus, obturator extenus.
Piriformis
intercostals
A synergist muscle is a muscle that aids another by promoting the same movement.
water
The gastrocnemius is a synergist of the soleus.
Agonist muscles are the primary muscles responsible for producing movement. However, synergist muscles are helper muscles that assist the agonist in executing a particular movement. Synergists help stabilize the movement and control the direction in which the force is exerted.
They are :bicsps, brachii,thoracis, dorsi, andmajor
iliacus,psoas major adductor longus ,piriformis
Some of the synergist muscles in the human body are the masseter, temporalis, supraspinatus, and the extensor digitorum. Examples if the antagonist muscles are the flexor digitorum superficial is, triceps brachii, extensor carpi radials longus, and the internal intercostals.
The Figure 4 stretch primarily works the gluteus maximus and piriformis muscles in the buttocks.
infraspinatus and teres minor
The agonist being the biceps brachii group. The two synergist muscles that assist the biceps brachiiare the brachialis and to a lesser extent the brachioradialis.