agonist muscle

agonist muscle

Controlled movements involve two opposing muscles: the agonist muscle produces the main action, while the antagonist muscle produces the opposite action to a lesser degree. The balance between agonist and antagonist muscles allows precise control of the final action.

Synonym: antagonist muscle See: PNF Stretching Techniques

See also: muscle

agonist muscle prime mover (see agonist)

• antagonist muscle muscles or muscle groups which neutralize action of another muscle or muscle group (see antagonist; muscle contraction)

• cardiac muscle; myocardium striated heart muscle

• involuntary muscle smooth muscle, not under voluntary control

• muscles of sole of foot see Table 1, and see named individual muscles

• muscle stretch reflex see reflex, deep tendon

• prime mover muscle see agonist

• skeletal muscle voluntary muscle attached at one or both ends to bone, crossing a joint or joints, and formed of elongated, multinuclear, transversely striated contractile fibres

• smooth muscle muscle tissue under involuntary (autonomic) control, e.g. vascular smooth muscle

• striated muscle skeletal and cardiac muscle; constituent fibres show cross-striations

• voluntary muscle skeletal muscle, i.e. muscle tissue that contracts in response to a decision to move or in response to reflex action (contrast with muscle, involuntary)

Table 1: Structures of the sole of the foot (superficial to deep) (see also Table J2)

Layer	Structure
0	Plantar aponeurosis (plantar fascia)
I	Muscles: abductor hallucis; flexor digitorum brevis; abductor digiti minimi Nerves: plantar digital nerves Vessels: plantar digital vessels
II	Nerves: lateral plantar nerve; medial plantar nerve Vessels: superficial branches of the medial and lateral plantar arteries
III	Tendons: tibialis posterior; flexor hallucis longus; flexor digitorum longus Muscles: flexor accessories (quadratus plantae); lumbrical muscles
IV	Muscles: flexor hallucis brevis; adductor hallucis; flexor digiti minimi brevis
V	Nerves: lateral plantar artery (deep branches) Vessels: lateral plantar artery (deep branches)
VI	Ligaments: deep plantar ligaments Tendons: peroneus longus; tibialis posterior Muscles: interossei Vessels: perforating branches of the plantar metatarsal arteries

Table 2: Movements occurring about the joints of the lower limb and foot

Movement about joint	Muscle causing the movement	Nerve supply to muscle
Hip flexion	Iliacus Psoas major Rectus femoris Sartorius Tensor fasciae lata Pectineus Adductor longus Adductor brevis	Ventral rami of L1 and L2 Ventral rami of L1 and L2 Femoral Femoral Superior gluteal Femoral Obturator Obturator
Hip extension	Gluteus maximus Semimembranosus Semitendinosus Biceps femoris, long head Adductor magnus, ischial part	Inferior gluteal Tibial part of sciatic nerve Tibial part of sciatic nerve Tibial part of sciatic nerve Tibial part of sciatic nerve
Hip adduction	Adductor longus Adductor brevis Adductor magnus Gracilis Pectineus Quadratus femoris	Obturator Obturator Obturator Obturator Femoral Ventral rami of L4, L5 and S1
Hip abduction	Gluteus medius Gluteus minimus Tensor fasciae lata Piriformis Obturator internus, in flexion	Superior gluteal Superior gluteal Superior gluteal Ventral rami of L5 and SI Ventral rami of L5 and S1
Medial rotation of leg at hip	Tensor fasciae lata Gluteus minimus Anterior fibres of gluteus maximus Adductors longus, brevis and magnus Iliopsoas	Superior gluteal Superior gluteal Superior gluteal Superior gluteal Ventral rami L1 and L2
Lateral rotation of leg at hip	Sartorius Gluteus maximus Obturator internus Gemelli Obturator externus Quadratus femoris Piriformis, in flexion	Femoral Inferior gluteal Ventral rami of L5, S1 and S2 Ventral rami of L5, S1 and S2 Obturator Ventral rami of L4, L5 and S1 Ventral rami of L5, S1 and S2
Knee flexion	Semimembranosus Semitendinosus Biceps femoris, long head Biceps femoris, short head Gracilis Sartorius Popliteus Gastrocnemius	Sciatic (tibial) Sciatic (tibial) Sciatic (tibial) Common peroneal Obturator Femoral Tibial Tibial
Knee extension	Vastus medialis Vastus lateralis Vastus intermedius Rectus femoris Gluteus maximus Tensor fasciae lata	Femoral Femoral Femoral Femoral Inferior gluteal Superior gluteal
Lateral rotation of leg = medial rotation of thigh in knee flexion	Biceps femoris, long head Biceps femoris, short head Gluteus maximus Tensor fasciae lata	Tibial Common peroneal Inferior gluteal Superior gluteal
Medial rotation of leg with knee flexed	Popliteus	Tibial
Medial rotation of leg with knee extended	Semimembranosus Semitendinosus Gracilis Sartorius	Sciatic (tibial) Sciatic (tibial) Obturator Femoral
Ankle plantarflexion	Gastrocnemius Soleus Plantaris Tibialis posterior Flexor hallucis longus Flexor digitorum longus Peroneus longus Peroneus brevis	Tibial Tibial Tibial Tibial Tibial Tibial Superficial peroneal Superficial peroneal
Ankle dorsiflexion	Tibialis anterior Extensor hallucis longus Extensor digitorum longus Peroneus tertius	Deep peroneal Deep peroneal Deep peroneal Deep peroneal
Subtalar and midtarsal inversion	Tibialis anterior Extensor hallucis longus Tibialis posterior	Deep peroneal Deep peroneal Tibial
Subtalar and midtarsal eversion	Peroneus longus Peroneus brevis Extensor digitorum longus Peroneus tertius	Superficial peroneal Superficial peroneal Deep peroneal Deep peroneal
1 Toe plantarflexion (MTPJ; IPJ)	Flexor hallucis longus Flexor hallucis brevis	Tibial Medial plantar
2–5 Toes plantarflexion (MTPJs; IPJs)	Flexor digitorum longus Flexor accessorius (quadratus plantae) Flexor digitorum brevis Lumbricals Interossei	Tibial Lateral plantar Medial plantar Medial plantar, toe 2; lateral plantar toes 3–5 Lateral plantar
1 Toe dorsiflexion	Extensor hallucis longus Extensor hallucis brevis	Deep peroneal Deep peroneal
2–5 Toes dorsiflexion 2–4 Toes dorsiflexion	Extensor digitorum longus Extensor digitorum brevis	Deep peroneal Deep peroneal
Toe abduction (away from midline of foot = adduction toward midline of body)
Toe 1 Toes 2–4 Toe 5	Abductor hallucis Dorsal interossei Abductor digit minimi	Medial plantar Lateral plantar Lateral plantar
Toe adduction (toward the midline of foot = abduction away from midline of body)
Toe 1 Toes 2–5	Adductor hallucis* Plantar interossei	Lateral plantar Lateral plantar
Note: Primary action of muscles is printed in normal type; muscles that give some contribution to this action are printed in italics . The nerve supply to the lower limb (lower leg and foot) is derived from the sciatic and femoral nerves. Dysfunction or compromise of either of these nerves causes marked motor, sensory and autonomic effects in the lower leg and foot. MTPJ, metatarsophalangeal joint; IPJ, interphalangeal joint.