Ground Reaction Forces from Depth Jumps at Different Heights do not Support Standard Weight Limitations

Document Type

Article

Publication Date

5-2011

Publication Title

Medicine & Science in Sports & Exercise Supplemental

DOI

10.1249/01.MSS.0000402316.48479.ee

ISSN

1530-0315

Abstract

Depth jump (DJ) exercises are effective tools used by strength and conditioning specialists when attempting to maximize results of plyometric training. In an attempt to reduce risk of injury during the performance of DJ, it is the position of an international strength and conditioning organization that athletes weighing over 220 lb not drop from heights greater than 46 cm. There is a dearth of literature supporting this recommended standard, which is of particular importance given the percentage of athletes in many sports weighing in excess of 100kg (220 lb).

PURPOSE: To determine peak vertical ground reaction forces (vGRF) relative to subject body weight (BW) from DJ at varied heights in college-age males.

METHODS: Thirty-three physically-active male college-age subjects (22.8±2.5yrs, 177.8±7.2cm, 80.6±14.1kg) with prior plyometric training experience performed DJ from heights of 30 cm, 45 cm, 60 cm, 75 cm, and 90 cm in random order. Subject body masses ranged from 53.3 to 103.7kg. Four trials from each height were completed. Subjects dropped onto two forceplates, from which the total vGRF was computed. Peak vGRF were determined and expressed in body weight units. Separate Pearson Correlation Coefficients between body mass and peak vertical GRF at each DJ height were used for statistical analyses.

RESULTS: No significant correlations existed between body mass and peak vGRF at any of the DJ heights: 30cm (r=.029, P=.872), 45cm (r=.002, P=.993), 60cm (r=-.244, P=.171), 75cm (r=.093, P=.609), and 90cm (r=.085 P=.639). Additional statistical comparisons of the body mass extremes (subjects with body mass below 150 lb; subjects with body mass above 220 lb) revealed no significant difference in peak vGRF at any of the DJ heights (P=.263 to.943).

CONCLUSION: Although we only had a few subjects over 100kg, the intensity of the peak vGRF relative to body weight do not appear to be related to body mass. Thus, these data support neither the notion that risk of injury during performance of DJ increases with BW at any particular DJ height nor the standard recommendation that the BW of 220 lb is a threshold for injury risk for DJ from heights greater than 46cm.

Comments

© 2011 American College of Sports Medicine

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