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Technical Details

  • Variable Type: Discrete Metric
  • Data Type: Float
  • Units: N/A (ratio/factor)
  • Column Name: twist_trunk_arm_speedup
  • Measurement: Ratio (or factor) of peak upper arm twist angular velocity to Peak Torso Twist Angular Velocity—how much the upper arm twist speeds up relative to the torso

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Description

Twist trunk arm speedup quantifies the increase in peak twist angular velocity from the torso to the upper arm during the serve. A value greater than 1 indicates the upper arm reaches a higher peak twist angular velocity than the torso, supporting efficient Twist Kinematic Sequence.

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Use Cases

  • Twist kinetic chain and energy transfer
  • Technique quality (proximal-to-distal speedup)
  • Coaching and training feedback