Original articles  EXERCISE PHYSIOLOGY AND BIOMECHANICS 

The Journal of Sports Medicine and Physical Fitness 2002 June;42(2):141-51

Copyright © 2009 EDIZIONI MINERVA MEDICA

language: English

Evaluation of methods for normalizing muscle strength in elite and young athletes

Jaric S., Ugarkovic D., Kukolj M.

From the Centre for Musculo-Skeletal Research, National Institute for Working Life Umea, Sweden and Institute for Medical Research Belgrade, Yugoslavia *The Research Center, Faculty for Sport and Physical Education Belgrade, Yugoslavia

Back­ground. The fol­lowing equa­tion has ­been ­most ­often ­used in ­order to ­present ­recorded ­muscle ­strength (F) nor­mal­ised for var­ious meas­ures of ­body ­size (­such as ­body ­mass m) ­Fnor = F·m-b. ­Since pre­vious ­studies ­have pro­vided incon­sis­tent ­results, the pur­pose of the ­present one was to ­assess the ­value of the expo­nen­tial param­eter b (b-­value) ­that (a) pro­vides ­both the nor­mal­ised ­strength inde­pen­dent of ­body ­mass and (b) dem­on­strates the ­highest pos­sible cor­re­la­tion ­between the nor­mal­ised ­strength and stan­dard ­tests of move­ment per­for­mance.
­Methods. Thir­teen ­groups of ­male and ­female ath­letes of ­both dif­ferent age and dif­ferent ­sport spe­cial­isa­tion ­were ­tested for max­imal iso­metric ­force of var­ious leg ­muscle ­groups, as ­well as for ver­tical and ­standing ­long ­jump.
­Results. The ­data ­obtained on ­most of the experi­mental ­groups sug­gested ­that the b-­value ­close to the theo­ret­i­cally pre­dicted b=0.67, but ­also dif­ferent ­from b=0 and b=1, ­should be ­used for cal­cu­la­tion of the nor­mal­ised ­strength inde­pen­dent of ­body ­mass. ­Although the ­strength nor­mal­ised ­using b=0.67 and b=1 dem­on­strated ­higher cor­re­la­tion ­with ­jumping per­for­mance ­than the non-nor­mal­ised ­strength (i.e., b=0), the ­data ­also sug­gested ­that b>1 ­could pro­vide the ­highest pre­dic­tion of move­ment per­for­mance.
Con­clu­sions. ­Muscle ­strength ­should be cal­cu­lated as ­force per kg2/3 ­rather ­than as abso­lute ­force or ­force cal­cu­lated per kg of ­body ­mass in ­order to ­assess ­strength inde­pen­dent of ­body ­size in rou­tine ­testing of ­muscle func­tion. How­ever, dif­ferent and prob­ably ­task spe­cific nor­mal­isa­tion ­methods ­could be ­required in ­order to pre­dict per­for­mance of var­ious move­ment ­tasks by ­assessed ­muscle ­strength.