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The Journal of Sports Medicine and Physical Fitness 1999 September;39(3):253-8


lingua: Inglese

Comparison of two abdominal training devices with an abdominal crunch using strength and EMG measurements

Demont R. G. 1, Lephart S. M. 1, Giraldo J. L. 1, Giannantonio F. P. 1, Yuktanandana P. 3, Fu F. H. 2

1 Neuromuscular Research Laboratory, University of Pittsburgh, Pittsburgh, PA, USA; 2 Department of Orthopaedics, University of Pittsburgh Medical System, Pittsburgh, PA, USA; 3 Department of Orthopaedics, Chulalongkorn University, Bangkok, Thailand


Background. The pur­pose of ­this ­study was to com­pare the train­ing ­effects of the Ab-Flex (F), Ab-Roller (R) and stan­dard ­crunch (C) on EMG pro­duc­tion, iso­met­ric max­i­mum vol­un­tary con­trac­tion (MVC), and iso­ki­net­ic aver­age ­peak ­torque at 30°/sec (ISO) of the abdom­i­nal mus­cles. It was hypoth­e­sized ­that the train­ing devic­es ­would ­have sim­i­lar val­ue in a ­strength train­ing pro­gram.
Methods. Experimental design: this was a pros­pec­tive ­study involv­ing 18 train­ing ses­sions of pro­gres­sive­ly increas­ing rep­e­ti­tions. Setting: Neuromuscular Research Laboratory, University of Pittsburgh. Subjects: thirty-two sub­jects vol­un­teered for ­this ­study, but ­only 26 com­plet­ed the train­ing. Each sub­ject par­tic­i­pat­ed in rec­re­a­tion­al activ­ity, but had not per­formed any abdom­i­nal train­ing ­prior to start­ing ­this ­study. Each sub­ject was ran­dom­ly ­assigned to ­either the con­trol ­group or one of the treat­ment ­groups. Interventions: there ­were ­three inter­ven­tions: two train­ing devic­es (Ab-Flex and Ab-Roller) and the stan­dard ­crunch, con­sid­ered a con­trol ­group. Measures: the pretest con­sist­ed of ­skin ­fold meas­ure­ments (%), EMG activ­ity (V) dur­ing the ­three inter­ven­tions, and ­peak ­torque (Nm) ­plus EMG dur­ing the MVC and ISO ­tasks. The 18 train­ing ses­sions ­over ­three ­weeks con­sist­ed of ­three ­sets of exer­cise ­with increas­ing rep­e­ti­tions ­from 10 to 20, by 2, eve­ry ­three ses­sions. The dif­fer­ence in ­pretest/­post­test ­scores ­were com­pared ­using a One-way ANO­VA on the ­mean dif­fer­enc­es (Mdiff) for ­each of: MVC, ISO (­peak ­torque), and EMG for ­upper rec­tus (UR), low­er rec­tus (LR), inter­nal ­oblique (IO), and exter­nal ­oblique (EO). A T-Test was ­used to ­detect sig­nif­i­cance for the ­body fat meas­ures.
Results. Mean dif­fer­enc­es (Mdiff) ­were nor­mal­ly dis­trib­ut­ed ­about ­zero for ­both MVC and ISO (MVC= -0.55, ISO=4.57). The anal­y­sis by ­group ­showed no dif­fer­ence (p=0.596) on the report­ed ­means (Nm) -3.16 (C), 5.84 (F) and -4.83 (R). The ­change asso­ciat­ed to the treat­ment dur­ing MVC was ­only 4% (η=0.04). For the ISO the Mdiff (Nm) ­were 1.39 (C), 13.66 (F) and -2.06 (R) ­which ­were not sig­nif­i­cant (p=0.127). The Ab-Flex was the ­only ­group to ­have a 95% con­fi­dence inter­val ­above ­zero, increas­ing by an aver­age of 16.5%. There ­were no sig­nif­i­cant dif­fer­enc­es for the EMG activ­ity for Mdiff or ­between ­group ­scores.
Conclusions. No sig­nif­i­cant dif­fer­enc­es ­were ­found ­with ­this ­study. These ­results ­would sug­gest ­that ­using ­these devic­es ­does not add sig­nif­i­cant­ly to over­all abdom­i­nal ­strength devel­op­ment, or reduc­tion of ­body fat. A sug­ges­tion ­could be ­made ­that cer­tain devic­es influ­ence mus­cles dif­fer­ent­ly.

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