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Mechanisms underlying the reduced performance measures from using equipment with a counterbalanceweight system.
MedLine Citation:
PMID:  22190164     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Bench press throws are commonly used in the assessment of upper body power and are often performed on a Smith machine thatutilizes a counterbalance weight to reduce the net load on the barbell. The use of a counterbalanced Smith machinewas recently shown to reduceperformance measures, but the mechanisms for this reduction have not been established. The purpose of this study was to determine the underlying physiological and biomechanical causes of the reduced performance measures found when using a counterbalanced Smith machine. Twentyfour men (mean ± SE: 23± 1 years, 91.0±3.5 kg, 178.9±1.2 cm)performed Smith machinebench press throws at 30% of one-repetition maximum under four conditions:1) rebound movement and counterbalance, 2) rebound movement and no counterbalance, 3) concentric only movement and counterbalance, and 4) concentric only movement and nocounterbalance. Peak power, peak force, and peakconcentric and eccentric velocities were measured using a linear accelerometer and peak ground reaction force was measured using a forceplate. The counterbalance condition produced significantly (p<0.05) lower peak accelerometer based force (-21.2% and -17.0% for rebound and concentric only bench press throws, respectively) but increased peak ground reaction force (5.3% and 3.2%). The discrepancy between changes in peak accelerometer based force and peak ground reaction force suggests that an increase in net external load occurred during the movement. Forperformance testing of explosive movementsthe use of a counterbalance system results inan underestimation of performance capability, likely due to an increase in the net external load during the concentric phase. Therefore, acounterbalance system should not be used for explosive movement performance testing.
Authors:
Harsh H Buddhadev; Jakob L Vingren; Anthony A Duplanty; David W Hill
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2011-12-20
Journal Detail:
Title:  Journal of strength and conditioning research / National Strength & Conditioning Association     Volume:  -     ISSN:  1533-4287     ISO Abbreviation:  -     Publication Date:  2011 Dec 
Date Detail:
Created Date:  2011-12-22     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9415084     Medline TA:  J Strength Cond Res     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
Applied Physiology Laboratories, Department of Kinesiology, Health Promotion and Recreation, University of North Texas, Denton, Texas, USA.
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