Prognostic Factors of a Favorable Outcome Following an Exercise Program for Soldiers With Low Back Pain

Prognostic Factors of a Favorable Outcome Following a Supervised Exercise Program for Soldiers With Sub-acute and Chronic Low Back Pain

Low back pain (LBP) encompasses heterogeneous patients unlikely to respond to a unique treatment. Identifying sub-groups of low back pain may help to improve treatment outcomes. Our objective was to identify variables associated with a favorable outcome in soldiers with sub-acute and chronic LBP participating in a multi-station full-body supervised exercise program. The results obtained may permit generation of potential treatment effect modifiers that will eventually have to be validated before being recommended for clinical practice.

All participants took part in the 6-week exercise program, as well as in the two evaluation sessions (pre- and post- exercise program). At the initial evaluation, subjects completed forms and questionnaires on sociodemographics, symptomatology, comorbidities, work restrictions, pain and functional limitations and fear-avoidance beliefs. A physiotherapist measured their lumbar and hip mobility, conducted diagnostic and pain provocation tests and assessed endurance of the trunk muscles. Following the initial evaluation, subjects took part in the 6-week multi-station full-body supervised exercise program (2 to 3 sessions per week). The Oswestry disability questionnaire (ODI) was completed at the initial and at the final evaluations. The change in ODI score following the program was considered the principal measure reflecting favorable or unfavorable outcome.

An improvement of 50% in the initial ODI score was considered the reference standard to determine a favorable outcome. Univariate associations with favorable outcome were tested using chi-square or paired t-tests. Variables that showed between-group (favorable/unfavorable) differences were entered into a logistic regression after determining the sampling adequacy. Finally, continuous variables were dichotomized and the sensitivity, specificity and positive and negative likelihood ratios were determined for the model and for each variable.

Inclusion Criteria:

• episode of subacute or chronic LBP with or without radiation to the lower limbs
• minimal score of 17% on the Modified Oswestry Disability Index

Exclusion Criteria:

• previous surgery to the spinal column,
• lumber spine injection in the past two weeks
• signs of upper motor neuron lesions
• serious medical conditions (e.g. tumor, fracture, rheumatoid arthritis, osteoporosis)
• unavailability to participate in the 6-week exercise program