Sternocleidomastoid muscles
Flexor Muscles
A flexor muscle is a muscle which bends or flexes a limb. Most flexor muscles are located on the anterior aspect of the body.
Muscles of the wrists include carpal muscles and extrinsic hand muscles.
The muscles of the legs do not follow the generalization that extensor muscles are on the posterior and flexor muscles are on the anterior.
Flexor Muscles
The flexor muscles are used when bending forward at the waist. The flexor muscles are located in the cervical and lumbar spine.
The muscles that are power wrist flexors are the flexor carpi radialis and flexor carpi ulnaris.
tibialis posterior, flexor digitorum longus and flexor hallucis longus
ANTERIOR
Collectively known as the iliopsoas or inner hip muscles: Psoas majorPsoas minorIliacus muscleAnterior compartment of thighRectus femoris (part of the quadriceps muscle group)SartoriusOne of the gluteal muscles: Tensor fasciae lataeMedial compartment of thighPectineusAdductor longusAdductor brevisGracilis
Extensor muscles open a joint and are the opposite to flexor muscles, which close it. I imagine triceps are extensor, while biceps are flexor.
All skeletal muscles will have a flexor and an extensor. The flexor bends the joint. The extensor straightens it out again.