Effects of Low-Load Motor Control Exercises and a High-Load Lifting Exercise on Lumbar Multifidus Thickness: A Randomized Controlled Trial.

STUDY DESIGN: Randomized controlled trial.

OBJECTIVE: The aim of this study was to compare the effects of low-load motor control (LMC) exercises and a high-load lifting (HLL) exercise, on lumbar multifidus (LM) thickness on either side of the spine and whether the effects were affected by pain intensity or change in pain intensity.

SUMMARY OF BACKGROUND DATA: There is evidence that patients with low back pain (LBP) may have a decreased size of the LM muscles with an asymmetry between sides in the lower back. It has also been shown that LMC training can affect this asymmetry. It is, however, not known whether a high-load exercise has the same effect.

METHODS: Sixty-five participants diagnosed with nociceptive mechanical LBP were included and randomized into LMC exercises or a HLL exercise, the deadlift. The LM thickness was measured using rehabilitative ultrasound imaging (RUSI), at baseline and after a 2-month training period.

RESULTS: There were no differences between interventions regarding effect on LM muscle thickness. However, the analysis showed a significant effect for asymmetry. The thickness of the LM muscle on the small side increased significantly compared with the large side in both intervention groups, without influence of pain at baseline, or change in pain intensity.

CONCLUSION: At baseline, there was a difference in thickness of the LM muscles between sides. It seems that exercises focusing on spinal alignment may increase the thickness of the LM muscles on the small side, irrespective of exercise load. The increase in LM thickness does not appear to be mediated by either current pain intensity or the magnitude of change in pain intensity.

LEVEL OF EVIDENCE: 2.