Changes in muscle thickness after exercise and biofeedback in people with low back pain.

CONTEXT: Individuals with low back pain (LBP) have reduced function of the transversus abdominis (TrA) and lumbar multifidus (LM) muscles. Biofeedback during exercise may increase the ability to contract the TrA and LM muscles compared with exercise alone. OBJECTIVE: To compare TrA preferential activation ratio (PAR) and the percent change in LM-muscle thickness in patients with LBP history before and after exercise with or without biofeedback. DESIGN: Controlled laboratory study. SETTING: University research laboratory. PATIENTS: 20 LBP individuals, 10 exercise alone and 10 exercise with biofeedback. INTERVENTIONS: Patients were allotted to tabletop exercises in isolation or tabletop exercises with visual, auditory, and tactile biofeedback. MAIN OUTCOME MEASURES: TrA PAR and percent change in LM-muscle thickness. RESULTS: There were no differences between groups at baseline (all P > .05). Nonparametric statistics showed decreased resting muscle thickness for total lateral abdominal-wall muscles (P = .007) but not TrA (P = .410) or LM (P = .173). Percent TrA thickness increased from table to standing positions before (P = .006) and after exercise (P = .009). TrA PAR increased after exercise (pre 0.01 ± 0.02, post 0.03 ± 0.04, P = .033) for all patients and for exercise with biofeedback (pre 0.02 ± 0.01, post 0.03 ± 0.01, P = .037) but not for exercise alone (pre 0.01 ± 0.02, post 0.02 ± 0.05, P = .241). No group differences were observed for TrA PAR before (exercise 0.01 ± 0.02, exercise with biofeedback 0.02 ± 0.01, P = .290) or after exercise (exercise 0.02 ± 0.05, exercise with biofeedback 0.03 ± 0.01, P = .174). There were no group differences in LM percent change before exercise (P = .999) or after exercise (P = .597). In addition, no changes were observed in LM percent change as a result of exercise among all participants (P = .391) or for each group (exercise P = .508, exercise with biofeedback P = .575). CONCLUSION: TrA PAR increased after a single session of exercises, whereas no thickness changes occurred in LM.