Background: The biomechanics of diving requires complex postural and respiratory adaptations. Kinematic and volumetric analyses of the trunk using advanced motion capture provide crucial insights into compartment mechanics, motor control, and movement efficiency. Aim: This study presents preliminary findings on the volumetric contribution and motor asynchrony (via phase angles) of different trunk compartments in divers. Methods: Two male divers (age: 56 and 60 years; height: 1.81 and 1.88 m; mass: 96 and 96 kg) were evaluated. Kinematic data were recorded using an eight-camera optoelectronic system (120 Hz). Participants sat in the center of the capture volume with 89 retroreflective trunk markers attached to the trunk, performing tidal volume and vital capacity maneuvers. Trunk volume was calculated from 3D marker trajectories using a prism-based mathematical model, dividing the trunk into the Upper Thorax (UT), Lower Thorax (LT), and Abdomen (AB). The percentage of contribution of each compartment to the total volume, and the phase angles between the regions (UTxLT, UTxAB, and LTxAB) were analyzed. Ethics approval by CAAE 56335515.8.0000.5153. Results: The abdomen was the predominant compartment, contributing 45.0%-54.7% to the total volumetric variation. The UT contributed 24.6%-35.1%, while the LT contributed the least (15.8%-21.6%). Phase angle analysis revealed asynchronous coordination patterns: UTxLT ranged from -31.07° to 2.17°, UTxAB from -34.47° to 13.29°, and LTxAB from -9.29° to 13.84°. These values indicate distinct inter-compartmental delays and individualized kinematic strategies. Conclusion: Divers exhibit strong abdominal volumetric dominance and significant coordination asynchrony between thoracic and abdominal regions. Future research must compare these preliminary findings with a non-diver control group to determine if these patterns represent specific adaptations to diving.
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