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Turning a door knob
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Supinator muscle
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Action: forearm supination (rotate radius laterally)
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Innervation: posterior interosseous nerve (C7, C8)
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Pronator teres
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Action: pronation of forearm at proximal radioulnar joint; flexion of forearm at the elbow joint
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Innervation: median nerve (C6, C7)
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Pronator quadratus
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Action: forearm pronation
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Innervation: median nerve (anterior interosseous nerve, C7, C8)
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Throwing a baseball overhead
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Deltoid
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Action: flexion and internal rotation of arm (clavicular); abduction of arm beyond initial 15° (acromial); extension and external rotation of arm (spinal)
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Innervation: axillary nerve (C5, C6)
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Subscapularis
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Action: arm internal rotation; stabilizes humeral head in glenoid cavity
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Innervation: upper and lower subscapular nerves (C5 - C6)
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Infraspinatus
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Action: arm external rotation; stabilizes humeral head in glenoid cavity
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Innervation: suprascapular nerve (C5, C6)
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Kicking a ball
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Vastus lateralis
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Action: extension of the knee
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Innervation: femoral nerve (L2-L4)
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Iliopsoas
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Action: main flexor of hip joint; psoas major and iliacus produce flexion of hip
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Innervation: lumbar spinal nerves (L2-L3)
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Rectus femoris
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Action: thigh flexion; knee extension; assist iliopsoas in hip flexion
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Innervation: femoral nerve (L2-L4)
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Doing sit-ups
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Rectus abdominis
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Action: trunk flexion; compresses abdominal viscera; expiration
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Innervation: intercostal nerves (T7-T11), subcostal nerve (T12)
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Transverse abdominis
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Action: compresses abdominal viscera, expiration (bilateral contraction); trunk rotation (unilateral contraction)
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Innervation: intercostal nerves (T7-T11), subcostal nerve (T12), iliohypogastric nerve (L1), ilioinguinal nerve (L1)
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Internal oblique
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Action: compresses abdominal viscera, trunk flexion, expiration (bilateral contraction); trunk lateral flexion, trunk rotation (unilateral contraction)
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Innervation: intercostal nerves (T7-T11), subcostal nerve (T12), iliohypogastric nerve (L1), ilioinguinal nerve (L1)
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Walking
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Soleus
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Action: soleus’ contraction results in strong plantar flexion; maintain upright posture
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Innervation: tibial nerve (S1, S2)
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Gastrocnemius
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Action: plantar flexor; provide force behind propulsion for walking, running, jumping
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Innervation: tibial nerve (S1, S2)
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Tibialis anterior
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Action: foot dorsiflexion; foot inversion
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Innervation: deep fibular nerve (L4, L5)
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Breathing
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Diaphragm
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Action: depresses costal cartilages; primary muscle for breathing
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Innervation: phrenic nerves (C3-5)
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Internal intercostals
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Action: depress ribs during forced expiration; support intercostal spaces and thoracic cage
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Innervation: intercostal nerves
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External intercostals
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Action: elevate ribs during forced inspiration; supports intercostal spaces and thoracic cage
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Innervation: intercostal nerves
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