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Throwing a baseball overhead
Muscle 1: Pectoralis major
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Action: Adducts and medially rotates arm at shoulder joint; clavicular head flexes arm and sternocostal head extends a flexed arm to the side of trunk
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Innervation: Medial and lateral pectoral nerves Biceps brachii
Muscle 2: Biceps brachii
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Action: Flexes forearm at the elbow joint, supinates forearm at radioulnar joints, and flexes arm at the shoulder joint.
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Innervation: Musculocutaneous nerve
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Kicking a ball
Muscle 1: Fibularis (peroneus) longus
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Action: Plantar flexes foot at the ankle joint and pronates foot at intertarsal joints
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Innervation: Superficial fibular (peroneal) nerve
Muscle 2: Soleus
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Action: Plantar flexes foot at ankle joint
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Innervation: Tibial nerve
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Doing sit-ups
Muscle 1: Transversus abdominis
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Action: Compresses abdomen
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Innervation: Thoracic spinal nerves T8–T12, iliohypogastric nerve, and ilioinguinal nerve
Muscle 2: External oblique
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Action: Compress abdomen and flex vertebral column; laterally flex vertebral column
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Innervation: Thoracic spinal nerves T7–T12 and the iliohypogastric nerve
4. Breathing
Muscle 1: Diaphragm
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Action: Flattens during contraction of the diaphragm and expands the thoracic cavity for inhalation; moves superiorly and reduces the vertical dimension of the thoracic cavity for exhalation during relaxation of diaphragm
- Innervation: Phrenic nerve (C3–C5)
Muscle 2: Internal intercostals
- Action: Contraction draws adjacent ribs together to decrease anteroposterior and lateral dimensions of the thoracic cavity during forced exhalation
- Innervation: Thoracic spinal nerves T2-T12