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The Journal of Sports Medicine and Physical Fitness 1999 June;39(2):113-9

language: English

Reliability and valid­ity of a new ­device to meas­ure iso­met­ric ­strength in poly­ar­tic­u­lar exer­cises

Verdera F. 1, Champavier L. 2, Schmidt C. 1, Bermon S. 3, Marconnet P. 1

1 Laboratoire de Recherche sur les Activités Physiques et Sportives UFR ­STAPS, Université de Nice Sophia-Antipolis, Nice, France;
2 Berenice ­SARL, Mouans-Sartoux, France;
3 Laboratoire de Physiologie de la Faculté de Médecine de Nice, Nice, France


Background. The pur­pose of ­this ­study was to ­assess the valid­ity of a new ­device to eval­u­ate iso­met­ric ­strength dur­ing mul­ti-­joint exer­cise ­such as the ­squat or ­bench ­press.
Methods. The ­device ­used an ­electric ­motor-driv­en bar to simul­ta­ne­ous­ly gen­er­ate and meas­ure forc­es dur­ing ­weight lift­ing exer­cis­es. This new ­device and a ­force plat­form meas­ured the forc­es gen­er­at­ed by ­either the ­motor on a ­fixed tele­scop­ic ­steel gird­er (pas­sive con­di­tion) or a sub­ject push­ing ver­ti­cal­ly ­against the bar ­from ­three ­squat posi­tions (­active con­di­tion). In the pas­sive con­di­tion, 252 meas­ure­ments ­were ­made, ­with 3 ­trials for 6 bar ­heights and 14 bar ­loads. In the ­active con­di­tion, 8 ­young phys­i­cal­ly ­active stu­dents (age, ­height and ­body ­mass ­were 25.1±2.6 ­years , 179.3±7.2 cm and 82.0±9.9 kg, respec­tive­ly) per­formed 3 max­i­mal iso­met­ric ­strength (MIS) ­trials in ­each of the 3 ­squat exer­cise posi­tions (par­allel, ­half and quar­ter ­squat), and 3 addi­tion­al MIS ­trials in one posi­tion ran­dom­ly ­assigned two ­weeks lat­er to ­test ­inter-day reli­abil­ity.
Results. In the pas­sive con­di­tion, no dif­fer­enc­es ­were ­observed ­between the forc­es meas­ured by the ­force plat­form and the new ­device. The coef­fi­cient of lin­e­ar regres­sion (r) and the coef­fi­cient of vari­a­tion (CV) ­were 1 and ­below 0.23%, respec­tive­ly. In the ­active con­di­tion, the ­peak MIS meas­ured was 2828 N and the val­ues of r and CV ­were ­above 0.982 and ­below 5.96%, respec­tive­ly. The assess­ment of ­inter-day reli­abil­ity ­showed an r val­ue of 0.984 and a CV of 3.98%.
Conclusions. This ­study dem­on­strat­ed ­that the new ­electric ­motor-driv­en exer­cis­er pro­vides val­id and reli­able ­data ­when ­used to gen­er­ate forc­es and meas­ure iso­met­ric ­strength through­out the ­load and ­motion rang­es com­mon­ly ­used in ­squat exer­cise.

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