Throwing a ball overhand involves a stride, hip rotation, trunk rotation and forward arm movement.
1. Phase A/B is a stride. Thrower stands sideways set towards target. When the opposite leg moves out and onto toes at the point of thrust. The pivot foot braces against the ground and provides stability for the subsequent movements. During this phase there is a natural rotation of the hip and the trunk rotation follows. The hips rotate before the trunk and due to the stretching of the torso muscles there is a stronger muscle contraction which allows you to throw with more force. The stride provides balance and stability throughout the act of throwing the ball, and all of the large muscle movements are gross motor skills. 2. Phase B/C Following the trunk rotation the throwing arm cocks back with the forearm in slight external rotation the arm moves into horizontal scapula adduction while grasping the ball tightly, using fine motor skills. 3. Phase C/D following the scapula horizontal adduction the throwing arm pushes forward into horizontal adduction, the elbow joint straightens and the thrower releases the ball. This is where the greatest forces are used to accelerate the ball. All, in the same instant, the throwing side the foot moves forward providing stability while the trunk and hip rotate forward.
Phase A-B | | | | Joints Invovled | Movement | Prime Mover/Agonist Muscle | Plane of Movement | Ankle | opposite ankle slight flexion | Gastronemius, Solius, Tibialis Posterior | Sagittal | Knee | opposite slight flexion | Hamstrings (biceps femoris, semimembranosus, Semitendinosus) | Sagittal | Hip | opposite slight flexion | Iliopsoas | Sagittal | Trunk | Opposite of ball throwing arm rotates forward | External and internal oblique, multifundi, rotators all on opposite side |
