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Determination of Friction and Pulling Forces During a Weighted Sled Pull.
MedLine Citation:
PMID:  22964856     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
ABSTRACT: Pulling or pushing weighted sleds has been included in various exercise programs. Coaches and researchers may wish to calculate work performed or estimate forces during these exercises, which would involve calculating coefficients of friction: static friction coefficient (μs) and dynamic friction coefficient (μd). The purpose of this study was to establish a reliable method for determining μs, μd, and pulling forces while pulling a weighted sled with different loads in order to quantify horizontal forces and work performed for training, assessment, and/or research. A nylon tether was attached to a sled-mounted force transducer and a winch was used to pull the tethered sled at a constant velocity for 20 seconds. Three different loads were pulled: 44.8 kg (the unloaded weight of the sled), 90.0kg (44.8kg sled with an additional load of 45.2kg), and 136.2 kg (44.8kg sled with an additional load of 91.4kg). Each load was pulled ten times using the winch for a total of 30 trials. μs was 0.47±0.01 (mean±SD; CV = 2.2%), 0.42±0.01 (mean±SD; CV = 3.0%), and 0.39±0.01 (mean±SD; CV = 2.7%) while μd was 0.35±0.01 (mean±SD; CV = 1.6%), 0.33±0.01 (mean±SD; CV = 3.7%), 0.31±0.00 (mean±SD; CV = 1.0%) for 44.8kg, 90.0kg, and 136.2kg, respectively (p<.01). When all trials and loads were combined, μs = 0.43±0.04 and μd = 0.33±0.02 with CV of 8.3% and 5.6%, respectively. The friction coefficients determined in this study were very repeatable, as indicated by the low CV. Coaches, athletes, and researchers who wish to determine μs and μd for their own specific equipment and surfaces can use the methods described here to do so.
Authors:
Matthew J Andre; Andrew C Fry; Luke A Bradford; Kevin W Buhr
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-9-7
Journal Detail:
Title:  Journal of strength and conditioning research / National Strength & Conditioning Association     Volume:  -     ISSN:  1533-4287     ISO Abbreviation:  J Strength Cond Res     Publication Date:  2012 Sep 
Date Detail:
Created Date:  2012-9-11     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:
Biomechanics Laboratory, Department of Health, Sport, and Exercise Sciences, University of Kansas, Lawrence, KS, USA, 66045.
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