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Europa Medicophysica 1999 December;35(4):195-205


language: English

Reliability of functional tests for low back disorders. A review

Capodaglio P.

Ergonomics Unit, Rehabilitation Center of Montescano, “S. Maugeri” Foundation, IRCCS and Center for the Study of Motor Activities, Medical Center of Pavia, “S. Maugeri” Foundation, IRCCS, Pavia, Italy


The aim of ­this ­paper was to ­review the lit­er­a­ture con­cern­ing reli­abil­ity of ­strength and endu­rance ­tests to dis­cuss the clin­i­cal appli­cabil­ity of ­such ­tests or the even­tu­al ­need for new ­tests and ­study ­designs for the low ­back and abdom­i­nal mus­cles con­sid­er­ing ­strength and endu­rance. The lit­er­a­ture ­search for ­this ­paper was ­made in Medline Pubmed (1972-1999) ­with the fol­low­ing key-­words: “low-­back ­pain, func­tion­al capac­ity, ­strength, endu­rance, ­trunk mus­cles”. We includ­ed all stud­ies con­cern­ing ­strength or endu­rance ­test for the ­trunk or abdom­i­nal mus­cles in rela­tion to reli­abil­ity. We exclud­ed all the stud­ies meas­ur­ing reli­abil­ity ­with ­less ­than 30-min inter­val or ­less ­than 1-min ­pause ­between max­i­mal iso­met­ric con­trac­tions. Exclusion cri­te­ria ­were ­also: num­ber of sub­jects < 20, no infor­ma­tion on dis­tri­bu­tion of meas­ure­ments (­mean, stan­dard devi­a­tion, ­range of ­test and ­retest) pro­vid­ed, no ade­quate infor­ma­tion on ­study ­design, ­poor sta­tis­tics (i.e. Pearson r, ­ICCC with­out any fur­ther infor­ma­tion). We ­have ­reviewed the lit­er­a­ture con­cern­ing the ­intra- and ­inter-observ­er reli­abil­ity of the fol­low­ing ­tests ­used for low-­back dis­or­ders: max­i­mal vol­un­tary con­trac­tion in stand­ing and seat­ed posi­tion, iso­met­ric leg/­squat and ­back ­lift, endu­rance, stat­ic endu­rance in abdom­i­nal mus­cles, dynam­ic endu­rance of ­back exten­sors, dynam­ic endu­rance of abdom­i­nals, dynam­ic iso­ki­net­ic ­strength meas­ure­ments, repet­i­tive move­ments. So far, ­most of the cit­ed reli­abil­ity ­tests did not ­show defin­i­tive ­results. In clin­i­cal stud­ies ­patients are ­often ­used as sub­jects and the ­degree of bio­log­i­cal vari­a­tion of dis­tress may ­indeed ­have an ­effect on reli­abil­ity. In gen­er­al, ­inter-observ­er reli­abil­ity is slight­ly low­er ­than ­intra-observ­er reli­abil­ity. Inconsistencies in the instruc­tions to the sub­jects ­could part­ly ­account for ­this dif­fer­ence. The ­need of prop­er famil­iar­iza­tion has ­been ­shown in sev­er­al stud­ies and for ­almost eve­ry meas­ure. An actu­al cor­re­la­tion ­between ­trunk ­strength or endu­rance and occur­rence of LBP has not ­been clear­ly ­shown.
Whether ­lack of reli­abil­ity can ­explain the ­fact ­that no ­true pre­dic­tors of LBP has ­been ­found is debat­able. For ­strength meas­ure­ments ­this is prob­ably not the ­case: reli­abil­ity is in ­fact ­fair, but no pre­dic­tive indi­ca­tions ­have ­been ­found in ­large pros­pec­tive stud­ies. On the oth­er ­hand, endu­rance as meas­ured by the Sørensen ­test has ­shown ­some pre­dic­tive val­ue, but reli­abil­ity was ­more fluc­tu­at­ing. Recommendations for ­future ­research ­must there­fore ­address the devel­op­ment of new endu­rance ­tests ­with high­er reli­abil­ity.

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