Muscle activation timing and balance response in chronic lower back pain patients with associated radiculopathy

•Low back pain patients with radiculopathy were compared to controls.•Muscle activation timing and kinetic response to balance perturbations were analyzed.•Back pain patients had delayed lower limb muscle activation in arm raise trials.•Muscle activation sequencing differences were found during anticipated sudden loading.•Radiculopathy may contribute to lower limb neuromuscular changes impacting balance.

BackgroundPatients with chronic low back pain and associated radiculopathy present with neuromuscular symptoms both in their lower back and down their leg; however, investigations of muscle activation have so far been isolated to the lower back. During balance perturbations, it is necessary that lower limb muscles activate with proper timing and sequencing along with the lower back musculature to efficiently regain balance control.MethodsPatients with chronic low back pain and radiculopathy and matched controls completed a series of balance perturbations (rapid bilateral arm raise, unanticipated and anticipated sudden loading, and rapid rise to toe). Muscle activation timing and sequencing as well as kinetic response to the perturbations were analyzed.FindingsPatients had significantly delayed lower limb muscle activation in rapid arm raise trials as compared to controls. In sudden loading trials, muscle activation timing was not delayed in patients; however, some differences in posterior chain muscle activation sequencing were present. Patients demonstrated less anterior-posterior movement in unanticipated sudden loading trials, and greater medial-lateral movement in rise to toe trials.InterpretationPatients with low back pain and radiculopathy demonstrated some significant differences from control participants in terms of muscle activation timing, sequencing, and overall balance control. The presence of differences between patients and controls, specifically in the lower limb, indicates that radiculopathy may play a role in altering balance control in these patients.