Introduction • The two videos that are being analysed are: • Stefan Holm (Sweden) jumping at 2.34 meters unsuccessfully. • Stefan Holm (Sweden) Jumping at 2.34 meters Successful. The purpose of this presentation is to analyse two high jump techniques that could be improved. The analysis undertaken is from referenced biomechanical principles, Both videos are analysed by angle of curve at entry and then correlated to angle at take off. This gives us an idea of angular velocity before take off and whilst in flight phase.
Technical Analysis Approach • Approach Phase Tan and Yeadon (2004) Suggest that a tightening curve towards the end of the approach will lead to an increased inward lean velocity. This is important as the greater the velocity before takeoff the more chance of success. Figure 1. " Backward lean angle and inward lean angle are the angles made with the vertical by projections of the foot – centre of mass line FG on vertical planes parallel and perpendicular to the horizontal velocity v." (Tan and Yeadon 2004)
Technical analysis Continued Tan and Yeadon (2004) suggest that on approach the inward lean angle should be approximately 300 then decreased to 00 by the final foot take off. The tightening of this approach curve leads to an inwards lean rotational velocity which helps develop the somersaulting motion. Several coaches have suggested that the curved approach is useful in developing this somersaulting motion during the take-off phase (Fix, 1981; Jacoby, 1986; Paolillo, 1989 cited in Tan and Yeadon, 2004)
Approach Phase Unsuccessful Successful 31.8 27.5 On approach both attempts shows very little difference in inward lean angle although the successful jump has a larger lean angle therefore can create a larger angular velocity which will develop a more efficient somersault motion. This may be the reason the jump is successful.
Technical Analysis Takeoff • Depena (1980) suggested that the main purpose of the inward lean on approach is so, the performers are positioned leaning away from the bar. This will create a successful attempt. • Tan and Yeadon (2004) recommend that at take off the inward lean angle should decrease from 300 to 00. This will create a vertical takeoff velocity and slight anglular velocity to travel up and over the bar.
Technical analysis Continued • Takeoff Lees et al (2000) suggest that the arms in the takeoff phase have a greater influence on performance than the lead leg. The inside shoulder should not drop in towards the bar and both arms should be swung upwards with the free leg (Mac 1997). Grieg and Yeadon (2000) explain from their research that at leg plant (before take off) The greater the angle at the knee the higher the jump height. See Figure 2 Figure 2. Leg plant vs. Jump Height
Takeoff Phase Successful Unsuccessful 4.7 4.9 In both attempts at immediate toe off, Stefan Holm converts his inward lean to a near vertical takeoff. This is supported by Tan and Yeadon (2004) as a successful takeoff.
Takeoff Phase 2 Unsuccessful Successful 8.2 2.7 After immediate takeoff in the unsuccessful jump, Stefan Holms lowers his shoulder therefore his arm bends making his approach angle to the bar a lot greater. This makes his overall attempt lower and consequently he hits the bar making it an unsuccessful jump. The successful jump demonstrates what the literature suggests. Stefan keeps his vertical angle by not dropping his shoulder and has a greater angular velocity (see slide 6) which creates height and a well developed somersault rotation. The arms are one of the most important aspects and this is the key difference between the two techniques which allows Stefan to succeed.
References • Tan, J,C. and Yeadon, M,R. (2004) Why do high jumpers use a curved approach. Journal of Sports Sciences. 23(8): 775-780. • Lees, A, Rojas, J, Cepero, M, Soto, V, and Gutierrez, M. (2000). How the free limbs are used by elite high jumpers in generating vertical velocity. Ergonomics. 43(10); 1622-1636. • Depena, J. (1980) Mechanics of rotation in the Fosbury-flop. Medicine Science Sports and Exercise. 12(1): 45- 53. • Mac, B. (1997). High jump fosbury flop. http://www.brianmac.demon.co.uk/highjump/. [last revised 15/03/2007]. • Greig, M.P., and Yeadon, M.R. (2000). The Influence of Touchdown Parameters on the Performance of a High Jumper. Journal of Applied Biomechanics.16. 367-378.