A Preliminary Efficacy Study on the Effectiveness of Low-Level Light Therapy for Vocal Fatigue

Vocal fatigue is a common complaint of patients with voice disorder and is related to functional and/or organic voice disorders. Professional voice users, such as teachers and singers and actors, are particularly prone to vocal fatigue. It has been reported that vocal fatigue also associated with limitation to voice activities and participation. In patients with vocal fatigue, experience of inflammation and muscle pain are among possible symptoms and manifestations of the condition.

In literature, various definitions have been suggested for vocal fatigue. Welham and Maclagan defined vocal fatigue as the negative vocal adaptation led by prolonged use of voice, and it can consist of perceptual, acoustic or physiologic components of undesirable or unexpected functional changes in the laryngeal mechanism.

In exploring the nature of vocal fatigue, Titze capitalised on a generally recognised mechanism of muscle fatigue which comprised of a peripheral component and a central component. Specifically, for the peripheral component, fatigue may take place at the myo-neural junction, muscle membrane and endo-plasmic reticulum (i.e., the transmission mechanism) or the muscle filaments (i.e., the contractile mechanism), where depletion or accumulation of biochemical substances such as glycogen occurs.

Low-level light therapy (LLLT), also known as photobiomodulation (PBM) therapy, has been developed as a therapeutic procedure which involves the exposure to low levels of red and near infrared light to cells or tissues. It has been approved by the Food and Drug Administration (FDA) of the United States for aesthetic and medical purposes.

Ever since, it has been established as a non-invasive and safe approach for a number of medical processes, such as reducing inflammation, relieving pain, wound healing, skeletal muscle repair and treating neurological disorders. Specifically, its effectiveness on treating muscle fatigue was investigated with the focus placed on muscles such as bicep braquialis, quadriceps and orbicularis oris.