Long-term analyses of spastic muscle behavior in chronic poststroke patients after near-infrared low-level laser therapy (808 nm): a double-blinded placebo-controlled clinical trial

Abstract

Stroke results in impairment of basic motor functions, such as muscle weakness in limbs affected by spasticity, leading to peripheral fatigue and impaired functionality. The clinical use of photobiomodulation therapy (PBMT) has provided major advances in the treatment of muscular disorders and prevention of muscle fatigue. The aim of this study was to analyze the effects of two distinct therapies in biceps spasticity of chronic hemiparetic patients. We analyzed range of elbow motion, torque, electromyography, and mean spectral frequency after 10 sessions of PBMT (Laser 100 mW, 808 nm, 159.24 J/cm2/point, 5 J/point); PBMT active or placebo was associated with exoskeleton-assisted functional treatment. A double-blind placebo-controlled sequential clinical trial was conducted with 12 healthy volunteers and 15 poststroke patients who presented upper-limb spasticity. The healthy volunteers performed only the evaluation protocol, and the poststroke volunteers participated in three consecutive phases (PBMT, PBMT + exoskeleton, placebo + PBMT) with a washout period of 4 weeks between each phase. We could observe significant increases in range of elbow motion after PBMT from 57.7 ± 14 to 84.3 ± 27.6 degrees (p < 0.001). The root mean square (RMS) values also increased after PBMT + exoskeleton from 23.2 ± 15 to 34.9 ± 21 μV (p = 0.0178). Our results suggest that the application of PBMT may contribute to an increased range of elbow motion and muscle fiber recruitment, increases in muscle strength, and, hence, to increase signal conduction on spastic muscle fibers in spastic patients.