Low back pain suppresses preparatory and triggered upper-limb activation after sudden upper-limb loading

Area of Science:

• Neuroscience
• Human Motor Control
• Musculoskeletal Health

Background:

• Chronic low back pain (LBP) is linked to altered trunk muscle function.
• The impact of LBP on upper-limb muscle function remains unclear, suggesting potential systemic effects.
• Investigating upper-limb responses can reveal broader motor control implications of LBP.

Purpose of the Study:

• To determine how chronic low back pain affects biceps brachii muscle activation.
• To analyze muscle responses during sudden upper-limb loading in individuals with and without LBP.
• To explore if LBP influences anticipatory and reactive muscle activity in the arms.

Main Methods:

• A cross-sectional study compared 29 patients with chronic LBP to 22 healthy controls.
• Surface electromyography recorded biceps brachii activity bilaterally during expected and unexpected limb loading.
• Muscle activation was analyzed in the 150ms before and 150ms after loading (in 50ms intervals).

Main Results:

• Patients with chronic LBP exhibited decreased biceps brachii activation prior to expected loading (P=0.035).
• Reduced activation was also observed 100-150ms after unexpected perturbation (P=0.010).
• Muscle activation in the initial 0-100ms post-perturbation was comparable between groups.

Conclusions:

• Chronic LBP does not impair reflex activation in the biceps brachii.
• LBP is associated with diminished preparatory and triggered muscle responses in the upper limb.
• Findings suggest that chronic low back pain may disrupt higher-level motor control information processing.