Pumping technique of elite iQfoil windsurfers in ecological settings.

Windsurfing pumping is a key manoeuvre in the Olympic iQFOiL class, yet its on-water biomechanics and coordination remain undescribed. This exploratory study quantified in situ kinematics and inter-element coordination during upwind pumping in seven elite windsurfers. A board-mounted camera recorded 36 race-pace upwind pumping sequences, and OpenPose-based markerless motion capture was used to estimate centre of mass (COM), knee and trunk angles, and COM-to-sail (CTS) and COM-to-board (CTB) distances. We conducted laboratory validation trials of the pumping motion to compare the markerless approach with a marker-based motion capture system. Field data showed large ranges of motion in the knee (58.8 ± 12.0°), trunk (37.1 ± 10.8°), CTS (16.1 ± 4.0 %H; % of body height) and CTB (10.9 ± 3.0 %H). Cross-correlation analysis revealed synchronous coordination between CTS, knee and trunk (lags < 5% of the cycle) and antiphase coordination between CTS and CTB. Together, these findings identify a whole-body pumping strategy in which knee and trunk motion are tightly coordinated to drive CTS and provide quantitative targets for coaching, simulator design and lab to field integration.