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Technical Details

  • Variable Type: Event
  • Data Type: Integer
  • Units: Frame number
  • Column Name: ‘apex_event’
  • Required for QA: True
  • Measurement: Frame at which the dominant-side wrist reaches maximum height

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Description

Apex marks the instant when the dominant-side wrist joint center reaches its maximum height during the serve, which typically coincides with ball contact. Contact-phase metrics (elbow flexion, shoulder abduction, X factor, trunk tilt, wrist velocity, wrist height) are reported at this event.

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Use Cases

  • Ball contact timing
  • Contact-phase metrics (joint angles, wrist velocity, wrist height)
  • Acceleration phase end and follow-through start