In-vivo stress measurements in kitesurfing and wakeboarding: implications on load control and preventive approaches – an in-vivo field study

"Background The trend sports kitesurfing and wakeboarding are increasingly gaining popularity. Tricks and high jumps – both in the air and over obstacles – are performed with increasing difficulty. Repeated high loads on the body, particularly when landing after a jump, can lead to overuse and acute injuries directly related to peak forces, particularly in the lower extremities. There is a lack of detailed analyses of these forces resulting from wakeboarding or kitesurfing, although such data would be relevant for the analysis of injury mechanisms and the subsequent development of prevention strategies. This study is the first of its kind in which the loads on the lower extremity during wakeboarding and kitesurfing were subjected to in-vivo measurements during various maneuvers. Methods Six wakeboarders and 12 kitesurfers (6 with loop bindings and 6 with fixed bindings) were investigated (mean age 33.1 ± 9.9 years). Jump height, hang time, acceleration, and the maximum vertical ground reaction force of both feet during takeoff and landing were recorded by means of sensor insoles (Moticon, Germany) on the feet of the athletes and simultaneously by a height and acceleration sensor (PIQ Sport Intelligence) on the board. A statistical analysis was performed. Results The data showed that wakeboarders were exposed to higher loads than kitesurfers, with significant differences occurring only between wakeboarders and kitesurfers with loop bindings and between kitesurfers with loop bindings and fixed bindings. High mean forces occurred during the landing of wakeboarders (rear foot 24.24 N/kg ± 8.82; front foot 20.33 N/kg ± 5.05) compared to kitesurfers with loop bindings (rear foot 12.09 N/kg ± 5.6; front foot 12.23 N/kg ± 4.92) as well as partially in kitesurfers with fixed shoe bindings (front foot 13.61 N/kg ± 5.92). Forces during lift-off were comparable in the rear foot (wakeboarders, kitesurfers with fixed bindings, kitesurfers with loop bindings 14.17 ± 6.37 vs. 16.39 ± 4.99 vs. 14.72 ± 5.13 N/kg). Similarly, despite the higher average acceleration force of the wakeboarders (4.16 g ± 1.02), there was no statistically significant difference (p = 0.166) compared to the kitesurfers. Conclusion The in-vivo forces acting on the lower extremities during wakeboarding and kitesurfing are high (highest absolute values of 3012 N and relative values of 31.71 N/Kg). In addition, fixed boot bindings allow for the generation of higher forces than strap bindings. The results of our study have important implications on load control and preventive approaches in these two sports."