The sport of high jumping can be classified as the series of complex cyclic-acyclic movements where the main objective is to bring the jumper’s center of mass to a maximum height when crossing the bar. In terms of biomechanical characteristics, the high jump technique is defined by the following three interrelated phases: run-up phase, take-off phase, and flight or bar clearance phase.
Faculty of Sport at the University of Ljubljana
The Faculty of Sport at the University of Ljubljana, Slovenia, conducted a study aimed at establishing the optimal kinematic parameters of the take-off action. Biomechanical analysis was conducted using two synchronized cameras operating at a frequency of 50 Hz and one Mikrotron MotionBLITZ Cube high-speed camera with a 500 Hz frequency. Kinematic parameters were established using Ariel Performance Analysis System (APAS) 3-D software for video-based biomechanical analysis.
The study was carried out at the Športniathletic stadium at Kodeljevo in Ljubljana, Slovenia. Scientists video recorded an elite athlete executing ten high jumps with the bar placed at a height ranging from 2.00m (6.56’) to 2.25m (7.4’). The maximum height at which the jumper cleared the bar that day was 2.18m (7.15’). At the Beijing Olympic Games, this same athlete placed 12th in the finals, with 2.25 m.
Take-off phase is most important element of jump
To many coaches and high jumpers, the take-off phase is the most important element of technique. In the take-off phase, the horizontal velocity of the jumper’s center of mass transforms into vertical velocity. Take-off begins at the instant the jumper places their take-off foot on the ground and concludes when it loses contact with the ground, an entire process that lasts approximately 0.14 to 0.18 of a second. Distance from the take-off point to the bar depends on the velocity of the jumper, the run-up technique, and the bar-crossing technique.
Take-off analysis was captured using the Mikrotron MotionBLITZ Cube camera along with the company’s Digital Motion Analysis Recorder capable of capturing 6 seconds of movements at a frequency of 1000 frames/second at a resolution of 640 x 512 pixels. In this study the camera recording was set at a frequency of 500 frames/sec. The analyzed area of the last two strides and the take-off point was calibrated with a 1m x 1m x 2m reference scaling frame, and the calibration was based on eight reference angles. Length of the analyzed movement was defined by the ‘x’ axis, the height by the ‘y’ axis, and the depth by the ‘z’ axis. The horizontal (X), vertical (Y) and lateral (Z) components of the ground reaction force were measured and smoothed with a digital second-order 500 Hz Buterworth filter. The high-frequency video recordings were synchronized with the measurements of forces, using a specially designed program in the Matlab environment.
For analysis, the jumper’s body was digitally segmented into 15 sections, each defined by 18 reference points. Numerical data were smoothed with a 16-level digital filter. Dynamic parameters were measured using a force plate that was fastened at the take-off zone.
Smallest advantage in technique can make the difference
Based on this study it is possible to establish that efficiency in high jumping largely depends on the optimal take-off action defined by the horizontal velocity of the center of mass at the start and its vertical velocity at the end, as well as by the duration of the take-off phase. Results showed the jumper developed the highest ground reaction force in the second phase of the take-off action, known as the “eccentric” phase. The ground reaction force in the vertical direction exceeded the jumper’s body weight by 5.6 times. In the last phase of the take-off called the “concentric” phase, the maximum ground reaction force was 9% lower compared to the eccentric phase. The University published its study in the Serbian Journal of Sport Sciences, titled “Biomechanical Characteristics of Take Off Action in High Jump-A Case Study” by Milan Coh.
Using Mikrotron cameras and recording equipment is helping coaches and elite athletes around the world perform at world-class levels of competition where the smallest advantage in technique can spell the difference between victory and defeat.