Pose 22 -

| Model | PCKh@0.5 (score) | Failure mode | |-------|----------------|--------------| | OpenPose (2017) | 0.68 | Left wrist hallucinated in empty space | | HRNet-W32 (2019) | 0.85 | Correct left wrist location but low confidence | | ViTPose (2022) | 0.92 | All keypoints within 10px of ground truth |

[3] Cao, Z., Hidalgo, G., Simon, T., Wei, S. E., & Sheikh, Y. (2019). OpenPose: Realtime Multi-Person 2D Pose Estimation. IEEE TPAMI .

Unlike canonical poses (e.g., "T-pose" or "A-pose") designed for clarity, Pose 22 represents a natural, unscripted human posture. Its study reveals the assumptions and limitations of current 2D keypoint detectors. This paper asks: What makes a pose "difficult" to estimate? How does a single index illuminate systemic dataset biases? And can such numerical identifiers translate across domains, from machine learning to dance notation? The MPII Human Pose Dataset contains approximately 25,000 annotated images across 410 activity classes [1]. Each image contains 16 anatomical keypoints (e.g., head, shoulders, elbows, wrists, hips, knees, ankles). Poses are indexed per image. pose 22

[2] Newell, A., Yang, K., & Deng, J. (2016). Stacked Hourglass Networks for Human Pose Estimation. ECCV .

| Joint Pair | Angle (deg) | Kinematic Significance | |------------|-------------|------------------------| | Shoulder-Elbow-Wrist (R) | 142° | Near-extension, reaching upward-right | | Shoulder-Elbow-Wrist (L) | 88° (occluded) | Flexed, hidden behind back | | Hip-Knee-Ankle (R) | 165° | Almost straight, weight-bearing | | Hip-Knee-Ankle (L) | 112° | Flexed, possibly lifted | | Neck-Shoulder (R/L) | 25° / -12° | Asymmetrical shoulder elevation | | Model | PCKh@0

The performance gap illustrates progress in handling self-occlusion and non-frontal views. Notably, Pose 22 is often included in ablation studies as a "hard example" due to its [2]. 5. Cross-Dataset Comparison: The Ambiguity of "Pose 22" Outside MPII, "Pose 22" appears in other datasets with entirely different meanings:

[4] Guest, A. H. (2005). Labanotation: The System of Analyzing and Recording Movement . Routledge. If you intended "Pose 22" to refer to a different domain (e.g., a specific yoga asana, a military drill position, a theatrical blocking notation, or a numbered pose in a specific fitness program), please provide that context and I will rewrite the paper accordingly. OpenPose: Realtime Multi-Person 2D Pose Estimation

| Dataset | "Pose 22" Meaning | Kinematic Pattern | |---------|-------------------|-------------------| | COCO WholeBody | Index 22 in person keypoint array | Standing, arms down | | Human3.6M | Subject S9, Action 22 (Sitting) | Seated, torso upright | | AMASS (MoCap) | Frame 22 of a specific sequence | Mid-stride walking |