Kinetic and Kinematic Analysis of Various Drop Jump Performances in Army Reserve Officer Training Corps Cadets

• Justin J. Merrigan ^[3] ; Kyle B. O'Toole ^[1] ; Clinton J. Wutzke ^[2] ; Margaret T. Jones ^[1]
  1. [1] George Mason University

     George Mason University

     Estados Unidos

     
  2. [2] Gonzaga University

     Gonzaga University

     Estados Unidos

     
  3. [3] Human Performance Innovation Center, Rockefeller Neuroscience Institute, West Virginia University, Morgantown, West Virginia

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• Localización: Journal of strength and conditioning research: the research journal of the NSCA, ISSN 1064-8011, Vol. 36, Nº. 3, 2022, págs. 738-746
• Idioma: inglés
• Texto completo no disponible (Saber más ...)
• Resumen

  • The purpose was to examine effects of sex, drop height, and external loads on drop jump mechanics in Reserve Officer Training Corps cadets and whether findings were associated with strength. Males (n = 14) and females (n = 12) completed maximal isokinetic concentric (slow-C and fast-C) and eccentric (slow-E and fast-E) knee extensions and flexions at 60[degrees][middle dot]s-1 and 180[degrees][middle dot]s-1. After 72 hours, 3 drop jumps were performed under 3 conditions (i.e., 30 cm unloaded [30UL], 30 cm loaded 15 kg [30L], and 60 cm unloaded [60UL]). No sex x condition interactions existed for any metric (p > 0.05). The 30L condition resulted in slower eccentric and concentric center of mass (COM) and angular velocities, reduced concentric vertical ground reaction forces (vGRF), and lower jump performances. Although 60UL resulted in greater eccentric COM and angular velocities, peak vGRF, impulse, and rate of force development (p < 0.008), no differences existed in jump performances. Males had faster COM and angular concentric velocities and smaller knee valgus angles, but no different vGRF compared with females. The change in the peak hip angle, because of 60UL, was associated with knee extension eccentric and concentric strength, whereas changes in knee angles were associated with eccentric strength. Likewise, eccentric strength influenced the effects of 30L on landing vGRF more so than concentric strength. Initial strength training is recommended, specifically emphasizing eccentric actions, before performing loaded (15 kg) drop jumps to reduce the increase of landing forces. However, caution may be required when performing drops from 60 cm because of increased forces, although no decline in jump performances were noted.