INTRODUCTION: In downhill skiing the mechanical potential energy gained during the ascent is partially lost by snow displacement during curves, but a great deal of energy dissipation is provided by lower limb muscles. Their eccentric contraction has been assessed during maximum damping maneuvers (drop landing) in the past (Minetti et al. 1998). Here we present an extended version of the previous test devoted also to evaluate the ability to manage very soft landings, which could be associated to a lower deceleration on snow. METHOD: Seven downhill skiers of the Italian A-team were asked to land on a Kistler platform from a height of 0.8 m. They were instructed: a) to stop the downward movement as fast as possible (hard landing, HOL) and b) to produce the lowest possible vertical ground reaction force (soft landing, SDL). Each trial was sampled at 1000 Hz and repeated 3 times. We measured: 1) impact force peak, 2) damping distance aftertouch down, 3) peak negative power produced by extensor muscles, and 4) time to speed reversal during landing. Also, we represented in a 'phase diagram' both HOL and SDL performances in terms of vertical Position of the body centre of mass (BCOM) against its vertical speed during the whole landing period (fig. 1). RESULTS: The HOL peak negative power during the post-impact damping was 54.0 ±11.3 W/kg. When compared to HOL, SDL resulted in a 54.6% greater damping distance (from 0.34 ± 0.08 to 0.51 ± 0.12 m), a 60.1% higher time to speed reversal (from 0.234 ± 0.067 to 0.359 ± 0.72 s), and a 39.2% lower impact force peak (from 8.29 ± 1.97 to 4.64 ± 1.76 kN). The 'phase diagram' (fig. 1) shows that, as expected, in both landing maneuvers touch down occurs at the same vertical speed of BCOM. HOL trajectory descends faster than SDL and reaches a stop (speed = 0) by means of a shorter downward displacement. DISCUSSION: The maximum negative power was found to be 62% higher than in the past (33.3 ± 8.1 W/kg, Minetti et al. 1998), probably due to the greater attention of modern training to eccentric exercise. The apparent similarity with the maximum positive power reported in the literature resides in having disregarded the energy dissipated during the early impact phase. The graphical representation of fig. 1 readily helps to visualize the extremes in performance (upper and lower curves) within which an athlete can modulate his/her action. CONCLUSION: With this study we propose a novel framework to evaluate the eccentric ability of skiers both in maximally damping and in fine modulating their force during jump landing.
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