Kinematics and Kinetics of Squats, Drop Jumps and Imitation Jumps of Ski Jumpers

Abstract

Pauli, CA, Keller, M, Ammann, F, Hübner, K, Lindorfer, J, Taylor, WR, and Lorenzetti, S. Kinematics and kinetics of squats, drop jumps and imitation jumps of ski jumpers. J Strength Cond Res 30(3): 643–652, 2016—Squats, drop jumps, and imitation jumps are commonly used training exercises in ski jumping to enhance maximum force, explosive force, and sport-specific skills. The purpose of this study was to evaluate the kinetics and kinematics of training exercises in ski jumping and to find objective parameters in training exercises that most correlate with the competition performance of ski jumpers. To this end, barbell squats, drop jumps, and imitation jumps were measured in a laboratory environment for 10 elite ski jumpers. Force and motion data were captured, and the influence of maximum vertical force, force difference, vertical take-off velocity, knee moments, knee joint power, and a knee valgus/varus index was evaluated and correlated with their season jump performance. The results indicate that, especially for the imitation jumps, a good correlation exists between the vertical take-off velocity and the personal jump performance on the hill (R = 0.718). Importantly, however, the more the athletes tended toward a valgus knee alignment during the measured movements, the worse their performance (R = 0.729 imitation jumps; R = 0.685 squats). Although an evaluation of the athletes' lower limb alignment during competitive jumping on the hill is still required, these preliminary data suggest that performance training should additionally concentrate on improving knee alignment to increase ski jumping performance.

Conditioning exercises in ski jumping: biomechanical relationship of squat jumps, imitation jumps, and hill jumps

“…The F max values relative to the average bodyweight and the v max values during the imitation jumps are comparable to those obtained by (Pauli et al, 2016). The F max values reported by Virmavirta and Komi (2001b) divided by the average body weight of the participants are also similar, although the v max during their imitation jumps was slightly smaller compared to the values of the present study.…”

“…The extra weight of the equipment was taken into account. The knee valgus/varus index (∆d*) at take-off was read out of the recorded videos from the frontal plane according to the methods of (Pauli et al, 2016). Three body angles (lower body angle (LBA), upper body angle (UBA) and knee joint angle (KJA)) were determined at the take-off from the sagittal plane videos (definitions see Figure 1).…”

“…Nevertheless, imitation jumps are relevant exercises for ski jumping training as they resemble hill jumps enough to be a valuable training method (Ettema et al, 2016;Müller, 2012). Pauli et al (2016) found significant correlations between the vertical take-off velocity (r = 0.718) as well as the valgus/varus index (r = 0.792) during imitation jumps and the performance of 10 athletes during competition. Virmavirta et al (2009) found a correlation (r = 0.628) between the official inrun velocity during hill jumps and jumping distance of 50 athletes.…”

“…Training exercises that have already been investigated include imitation jumps from a fixed platform, imitation jumps from a rolling platform with different inclination angles, squats, squat jumps, and drop jumps (Ettema et al, 2016;Fritz, Lindinger, & Schwameder, 2015;Pauli et al, 2016). For an imitation jump, the athlete stands on the platform in a squatting position and then mimics the take-off of a hill jump by jumping into the arms of the coach, who holds the athlete in the air to imitate the flight phase.…”

“…Whereas the athletes are equipped with their helmet, jumpsuit, jumping boots and wedge during hill jumps, they usually wear a normal t-shirt, shorts and indoor shoes during training sessions (Ettema et al, 2016;Pauli et al, 2016). While ski jumping boots do not allow any motion in the ankle, movements in all directions are possible for the ankle with indoor sport shoes.…”