Are the Kinetics and Kinematics of the Surf Pop-Up Related to the Anthropometric Characteristics of the Surfer?

The surf pop-up is a unique and challenging skill, critical to successful surfing. Hypothesizing that anthropometric characteristics of surfers influence the pop-up performance, we aimed to measure kinematics and ground-reaction forces (GRF) during a simulated pop-up motion, and to relate these variables with anthropometric characteristics. Twenty-three male surfers (age: 28.4 +/- 10.1 years old; body mass: 68.3 +/- 10.8 kg; height: 1.73 +/- 0.07 m; time of practice: 12.4 +/- 8.9 years; arm-span: 1.75 +/- 8.9 m) perform a simulated pop-up in the laboratory, while GRF and 3D motion-capture data were acquired. The duration of the pop-up was 1.20 +/- 0.19 s (60% push-up and 40% reaching/landing phase). During the push-up, the hands were placed 0.46 +/- 0.05 m apart and generated a relative total peak-force of 0.99 +/- 0.10 N/Weight, with symmetrical impulse of 0.30 +/- 0.05 N center dot s/Weight for the dominant and 0.29 +/- 0.07 N center dot s/Weight for the nondominant hand. Elbow angles were not different during the peak force application (110 +/- 18 degrees vs. 112 +/- 18 degrees, respectively) of the push-up phase. During the landing phase, the feet were placed 0.63 +/- 0.10 m apart and generated a relative peak force of 1.63 +/- 0.18 N/Weight. The impact force during landing was applied unevenly between the rear foot (28%) and the front foot (72%). In conclusion, most anthropometric-related variables showed no relationship with performance variables, with the exception of an inverse relationship between muscle mass and pop-up total duration. We also observed no differences in upper- and lower-body kinematics between the dominant vs. nondominant hands and among surfers who preferred a regular vs. "goofy-foot" stance. Finally, the force profiles between hands were similar and symmetric, while the lower extremities during the reaching phase were different, with the front foot applying greater force than that of the rear foot.