Due to the increasing number of athletes in the field of water sports such as wakeboarding or kitesurfing, typical injury patterns in the area of the lower extremity can be identified. The aim of this study is to measure the forces acting on the feet during wakeboarding and to derive preventive strategies.
Using the SCIENCE Insole2 sensor sole (Moticon ReGo AG, Munich, Germany), pressure loads were measured on both feet of male wakeboarders (n = 6, mean age 32.7 years, mean body weight 76kg) riding a water ski lift at 30 km/h for 5 minutes. In addition, a height and acceleration sensor (Fa. PIQ, Neuilly-sur-Seine/FRA) was used to collect data (jump height, acceleration during jump and landing). The sensor soles were integrated into the binding in such a way that normal movement was not impaired. During the study period, athletes completed various common sport-specific jumps. The loads were continuously recorded, then read out and evaluated.
With a jump height of mean 2.29m+-0.53 (1.0-3.3), the force applied to the feet during landing was mean 4.14g+-0.96 (2.8-6.2). The maximum pressure was 3.012N on the rear foot (mean 1.679N+-724 (622-3.012)) and mean 1.479N+-501 (510-2.355) on the front foot. Furthermore, it was shown that during landing, the heel of the rear foot (In the direction of travel) is loaded first; an increase in pressure (landing) of the front foot occurs with a time delay. Also during take-off, the values of the rear foot reach a maximum of 2.142N (mean 1.008N+-532 (108-2.142), those of the front foot a maximum of up to 1.618N (mean 878N+-415 (152-1.618). The highest values could be measured during landing after high, so-called "invert tricks" (wakeboard above the athlete's head height) with mean 2,355N+-535 (1,458-3,012) on the rear foot and mean 1,761N+-430 (1,208-2,355) on the front foot (see Fig. 1). Low jumps (so-called "bunny hops"), where the jump height is only less than one meter high, nevertheless reach values of mean 1,240N+-441 (748-1,813) on the rear foot and mean 1,408N+-621 (739-1,977) on the front foot. In contrast, the values for common jumps over so-called "obstacles" (obstacles) showed to be significantly lower (rear foot mean 975N+-260 (622-1,431); front foot mean 1140N+-444 (510-1,792)).
Compared to similar sports, the forces acting on the foot during wakeboarding are significantly higher. In a study of the so-called "ollie" in skateboarding, values of about 600N per foot could be measured. Injury mechanisms in wakeboarding can thus be better understood. The force peaks that occur especially during landing can lead to chronic overload damage (e.g. bone marrow edema) as well as cause acute injuries (e.g. fractures). The knee joint in particular is susceptible to injury due to the rigid fixation of the foot/upper ankle by the binding. The results of the study may provide valuable insights to guide training intensities and equipment advancements (e.g., cushioning systems, improved bindings).