Analysis of Landing in Ski Jumping by Means of Inertial Sensors and Force Insoles

Abstract

Landing and its preparation are important phases for performance and safety of ski jumpers. A correct ski positioning could influence the jump length as also the cushioning effect of the aerodynamic forces that permits the reduction of landing impacts. Consequently, the detection of ski angles during landing preparation could allow for analyzing landing techniques that result in reduced impact forces for the athletes. In this study, two athletes performed with force insoles and inertial sensors positioned on the ski during training conditions on the ski jumping hill. The results confirmed previous studies, showing that impact forces can reach more than four times body weight. In the analyzed cases, the force distribution resulted to be more concentrated on the forefoot and the main movement influencing the impact was the pitch. The combination of inertial sensors, in particular gyroscopes, plus force insoles demonstrated to be an interesting set up for ski jumping movement analysis.

Ground Reaction Forces and Kinematics of Ski Jump Landing Using Wearable Sensors

“…The outcomes of the force insoles during the entire performance (Figure 2) were comparable with those in previous publications [1,21,35]. The normal GRF max and the impulse were correlated with t flight (Table 1).…”

“…Regarding the limitations of the studies, as previously mentioned, the low sample rate of the force insoles could have influenced the collected outcomes [35]. Therefore, during further studies, a higher sampling rate (200 Hz) of the loadsol insoles would be recommendable.…”

“…Concerning the kinematic analysis, inertial motion units (IMUs), with their easy-to-use, accurate and wide recording volume characteristics, overcome the problems related to the inaccuracy and the long post-processing and positioning time of the video camera set-ups [30]. The IMUs have already shown their potential in ski jumping when positioned on the body [31,32,33] or only on the skis [34,35]. However, no studies have investigated the landing kinematics with the sensors positioned on the lower limbs, rather concentrating on the overall jump performance [31,32,33].…”

Aerodynamics of an isolated ski jumping ski

“…In the literature there is information on yaw (~ 15°-20°) and AoA angles (~ 25°-40°) used by ski jumpers during most of the flight phase (e.g., [4]), but less about roll of the ski around its longitudinal axis which corresponds to the edge angle described in the present study. Bessone et al [5] used inertial sensors to measure the edge angle of both skis during the flight phase of two jumpers. The angle ranged from 0° (flat ski) at the release instant from the take-off table to 30°-40° at mid-flight.…”

Ski Position during the Flight and Landing Preparation Phases in Ski Jumping Detected with Inertial Sensors

“…Therefore, a combination of IMUs placed on the skis and wireless force insoles could represent an interesting set-up for this analysis. This combination has been previously introduced by the authors of the present paper, and the first results showed that the ski position influences the vertical ground reaction force (GRF) [24]. The combination of IMUs and force insoles proposed in [24] was utilized in the present study on a higher number of ski jumpers to detect possible correlation between ski position and impact kinetics.…”