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Technical Details

  • Variable Type: Discrete Metric
  • Data Type: Boolean
  • Units: True/False
  • Column Name: trunk_not_stacked_flag
  • Aggregation: rate
  • Precision: 0
  • Optimal Direction: Lower is better
  • Unknown Value: -1
  • Measurement: Trunk flexion, lateral tilt, and twist (relative to pelvis) between high hand and release
  • Threshold: Any of trunk flexion, tilt, or twist exceeds 30°

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Description

Trunk not stacked is a binary indicator that flags when the trunk is excessively flexed, tilted, or twisted (more than 30° in any direction relative to the pelvis) during the delivery phase from high hand to release, which reduces the efficiency of the athlete’s posture over their base of support.

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Use Cases

  • Posture and stacking assessment
  • Mechanics evaluation

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Corrective Drills

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1. Posture Wall Drill

Stand tall with the back against a wall, then walk through the arm circle and delivery while keeping the trunk upright and stacked over the hips, minimizing lateral lean and excessive twist. Use the wall for tactile feedback on trunk position. Perform 3 sets of 10 slow repetitions. Search YouTube: softball pitching posture drill stacked trunk

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2. Video Pause at Release Drill

Throw at half-speed into a net while recording from the side and front. Pause the video at release to check that the trunk is upright and centered rather than excessively flexed, tilted, or twisted. Repeat and self-correct across repetitions. Search YouTube: softball pitching video analysis trunk posture release