Influence of Feedback Schedule in Motor Performance and Learning of a Lumbar Multifidus Muscle Task Using Rehabilitative Ultrasound Imaging: A Randomized Clinical Trial

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Background and Purpose: Low back pain (LBP) may be associated with inadequate multifidus muscle function. Varying the frequency and timing of feedback may enhance acquisition and retention of multifidus muscle recruitment during exercise. Subjects: Subjects without LBP (n=30) were randomly assigned to a constant (CON) or variable (VAR) feedback group. Twenty-eight subjects (mean age=28 years, SD=8.0; mean body mass index=24 kg/m2, SD=0.70) completed training, and 23 completed retention testing. Methods: Eight training sessions over 4 weeks included multifidus muscle exercise with rehabilitative ultrasound imaging (RUSI) feedback. Retention was assessed at 1 week and ≥1 month. Results: At the start, both groups had similar performances of multifidus muscle recruitment (Fisher exact test, P=.26). Early in training, the CON group had good success (mean=80%) that was maintained at session 8 (mean=84%), with no difference between sessions 1 and 8 (Wilcoxon signed rank test, P=.19, 95% confidence interval [CI]=-9%, 42%). The VAR group gradually increased success (Wilcoxon signed rank test, P=.002, 95% CI=17%, 59%) between sessions 1 and 8. Both groups sustained their session 8 success when tested for short-term retention at 1 week (CON group: Wilcoxon signed rank test, P=.79; VAR group: Wilcoxon signed rank test, P=.36). At the long-term retention test, the VAR group outperformed the CON group (Wilcoxon score test, P=.04), indicating superior motor learning. Discussion and Conclusion: Variable feedback provided by RUSI resulted in greater success in lumbar multifidus muscle recruitment up to 3 to 4 months after training.