BIOMECHANICS OF THROWING: PART 1

I’m sure many people can remember learning to throw at primary school… but, since then, have you put any thought into the biomechanics that are necessary to throw repetitively without injury?! The process of throwing is extremely complicated and requires the effective co-ordination of many body parts throughout several phases. So, what are these phases…

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PHASES OF AN OVERHEAD THROW

1. Wind-up

  • Lead leg lifts.
  • The stance leg is held slightly bent.
  • Low forces and muscle activity through the throwing arm.

2. Stride

  • Lead leg begins to move towards the target, generating linear velocity.
  • Arms start to separate, lift and the throwing arm begins to externally rotate.
  • The stride phase ends when the lead foot contacts the ground. At this point, the throwing elbow is flexed, shoulder is abducted to 90° and externally rotated.

3. Arm Cocking

  • To maintain stability, quadriceps in the lead leg activate shortly after lead foot contact.
  • The pelvis starts to rotate towards the target, initiating rotation through the upper body. As the pelvis and trunk rotate a large volume of energy is transferred from the lower limb and into the throwing arm.
  • As the upper body starts to rotate towards the target, the shoulder externally rotates to the point of maximum external rotation and horizontally abducts.
  • Shortly before the end of the arm cocking phase, elbow extension begins. From a maximum of 100° elbow flexion, it is essential that extension of the elbow begins before shoulder internal rotation starts.
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4. Arm Acceleration

  • This phase is the explosive portion of the throw between maximum shoulder external rotation and ball release.  
  • The trunk will flex forwards, a movement that is enhanced by the lead knee stabilizing which provides a stable base for the trunk to rotate on.
  • Maximum shoulder internal rotation velocity occurs near the time of ball release

5. Arm Deceleration

  • This is the short phase between ball release and maximum internal rotation, which continues until the arm is in a neutral position.

6. Follow-through

  • A long arc of deceleration from the throwing arm, flexion of the trunk and extension of the lead leg allows energy to be absorbed by the large muscles in the trunk and legs.
  • This phase helps reduce the stress through the throwing arm by transferring most of the momentum into the lead leg.

 

MUSCLES ACTIVATED WITH AN OVERHEAD THROW

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Phase Action Muscles active
Wind-up Maximum knee lift Quadriceps (vastus medialis, vastus lateralis, vastus intermedius, rectus femoris), iliacus, psoas

**Low muscle activation in this phase, largely preparing for second phase.

Stride Hip abduction and control of stance leg Glutes (obturator internus, superior/inferior gemelli, piriformis, gluteus maximus/minimus/medius), tensor fascia lata, sartorius
Knee and hip extension in stance leg Hamstrings (semimembranous, semitendinous, biceps femoris), glutes (obturator internus, superior/inferior gemelli, piriformis, gluteus maximus/minimus/medius)
Shoulder external rotation in throwing arm, horizontal shoulder abduction bilaterally Deltoid, rotator cuff (supraspinatus, infraspinatus, teres minor, subscapularis), upper trapezius, serratus anterior
Elbow flexion Biceps, brachialis, brachioradialis
Hyperextension of the wrist Wrist/finger extensors (extensor carpi radialis, extensor carpi ulnaris, extensor digitorum).
Arm Cocking Deceleration of knee flexion Quadriceps (vastus medialis, vastus lateralis, vastus intermedius, rectus femoris) eccentrically
Trunk rotation Abdominals (Rectus abdominus, obliques (internal and external), transverse abdominis), Lumbar/Thoracic stabilisers (multifidus, longissimus, iliocostalis)
Stabilization of the shoulder Levator scapulae, serratus anterior, trapezius, rhomboids, pectoralis minor
Shoulder external rotation and horizontal adduction Rotator cuff (supraspinatus, infraspinatus, teres minor, subscapularis), pectoralis major, latissimus dorsi, anterior deltoid, teres major.
Controlling/resisting valgus torque to elbow Triceps and anconeus (eccentrically)
Arm Acceleration Trunk flexion Rectus abdominus, obliques
Shoulder internal rotation Rotator cuff (supraspinatus, infraspinatus, teres minor, subscapularis), trapezius, serratus anterior, rhomboids, levator scapulae.
Elbow extension Triceps (concentrically); biceps, brachialis, brachioradialis (eccentrically).
Wrist flexion (to a neutral position) Flexor carpi radialis, flexor carpi ulnaris abd flexor digitorum, pronator teres
Arm deceleration Shoulder internal rotation Supraspinatus, infraspinatus, teres minor and major, latissimus dorsi, posterior deltoid
Controlling elbow extension and forearm pronation Biceps, brachialis, brachioradialis (eccentrically); supinator.
Deceleration of wrist/finger flexion Wrist/finger extensors (extensor carpi radialis, extensor carpi ulnaris, extensor digitorum) eccentrically.
Follow through Shoulder deceleration Supraspinatus, infraspinatus, teres minor and major, latissimus dorsi, posterior deltoid, trapezius, serratus anterior, rhomboids
Deceleration of wrist/finger flexion Wrist/finger extensors (extensor carpi radialis, extensor carpi ulnaris, extensor digitorum) eccentrically.
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WHAT CAN GO WRONG?!

Often, if one muscle isn’t working effectively the load will be shifted to another muscle, tendon, ligament, bone or joint. Stay tuned for part two, which will go into detail on the injuries commonly seen in throwing athletes… Alternatively, for more information call (03) 5229 3911 or email info@theinjuryclinic.com.au or click here to book an appointment with one of our Physiotherapists online.

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