An interventional study of photobiomodulation in Vocal Fatigue, sponsored by Chinese University of Hong Kong. Completed at 1 site in Hong Kong. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2025-07-14.
Sponsored by Chinese University of Hong Kong · Not applicable, Interventional, and Treatment
The goal of this phase 2 clinical trial is to examine the effectiveness of photobiomodulation in patients with vocal fatigue.
The main question it aims to answer is whether photobiomodulation is able to alleviate vocal fatigue in patients with diagnosed vocal fatigue.
Participants will ask to receive photobiomodulation treatment for 12 sessions over a three week period.
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.
These studies utilised the feature of LLLT to interact with muscle tissues and therefore provide physiological and/or therapeutics effects to reduce muscle fatigue and enhance muscle performance. Relating this to the fatigue resulting from prolonged voice use at the laryngeal level, it is possible for LLLT to be developed as a treatment approach for vocal fatigue.
In a Phase 1 study, the potential effectiveness of using LLLT in vocal fatigue treatment by applying red or infrared Lights to healthy individuals following vocal loading tasks was explored. The authors concluded that red light might be effective in improving vocal fatigue on aspects of acoustic, aerodynamic, and self-perceptual markers.
The proposed study will be a Phase 2 behavioural study-controlled trial on the effectiveness of LLLT on treating vocal fatigue.
The primary objective of this study is to investigate the effectiveness of lower-level light therapy on reducing vocal fatigue on self-perceptual phenomena exhibited by participants, as well as acoustic and aerodynamic changes in voice.
Vocal Fatigue Index (Hong Kong-Chinese Version) (VFI(HK)) will be used as the primary outcome measurement methods. Perceptual evaluation of voice, acoustic measurement, aerodynamics evaluation (by maximum phonation time (MPT)), vocal symptoms scale and Voice Handicap Index (VHI-30) will be used as secondary outcome measurements.
The current study will be a preliminary clinical trial to identify the therapeutic efficacy of PBM on laryngeal muscles as a new treatment for patients with vocal fatigue. It could act as a pilot study and results obtained could be a foundation for Phase 3 RCT studies to investigate using LLLT to treat vocal fatigue.
77 studies on the registry are indexed under Voice Disorders; 17 are open to participants now.
This study's enrollment of 22 is below the median of 41 across 54 interventional studies indexed under Voice Disorders.
Browse Voice Disorders studies →Chinese University of Hong Kong is the lead sponsor of 1,454 studies on the registry; 474 are open to participants now.
Of its 6 completed or terminated interventional studies of FDA-regulated products, 0 (0%) have results posted.
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Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Device: photobiomodulation
The output of the photobiomodulation device is listed as below: * Irradiation size: 15 cm × 10 cm * Dual-wavelength: 660 nm + 850 nm * Optical power density: 10 - 15 mW/cm2 * Dose density: 6J/cm2
Also known as: low level light therapy
Vocal Fatigue Measure: Vocal Fatigue Index (VFI-HK)
The VFI(HK) contains 19 items in three domains (i) tiredness of voice and avoidance of voice use (ii) physical discomfort and (iii) improvement of symptoms after rest. All items are rated on a scale from zero (0, meaning "never") to four (4, meaning "always"). The score ranges from 0 to 76, with higher score indicating worst outcome.
Time frame: This will be measured at baseline (pre-treatment) and within 2-weeks after the completion of treatment (post-treatment).
Vocal function measure: Voice Handicap Index - 30
The VHI-30 contains 30 items in three subscales, namely "Functional", "Physical " and "Emotional". All items are rated on a scale from zero (0, meaning "never") to four (4, meaning "always"). The highest possible score for the VHI-30 is therefore 129, with the higher indicating worst scores.
Time frame: This will be measured at baseline (pre-treatment) and within 2-weeks after the completion of treatment (post-treatment).
Vocal Function Measure: Aerodynamic assessment
Maximum phonation time will be used as the aerodynamic measure. Maximum phonation will be measured in seconds (time), with the higher score indicated better outcome.
Time frame: This will be measured at baseline (pre-treatment) and within 2-weeks after the completion of treatment (post-treatment).
Vocal Function Measures: Acoustic voice analysis
Four parameters will be measures: (i) Jitter - Jitter represents the cycle-to-cycle variation in the fundamental frequency of the voice signal. Healthy, sustained phonation in young adults typically shows jitter values between 0.5% and 1.0%. Values above 1% may suggest dysphonia. (ii) Shimmer: Shimmer represents the cycle-to-cycle variation in the amplitude of the voice signal. Shimmer values below 3% are generally considered normal. Higher shimmer values can indicate dysphonia. (iii) Harmonic to noise ratio: HNR quantifies the ratio of harmonic to noise components in the voice signal. A high HNR indicates a strong presence of harmonics, which is characteristic of a clear, healthy voice. A low HNR suggests a greater proportion of noise in the voice, which is often associated with hoarseness. (iv) CPPS: CPPS measures the prominence of the cepstral peak, which represents the periodicity in the voice signal. Lower CPPS values suggest dysphonia.
Time frame: This will be measured at baseline (pre-treatment) and within 2-weeks after the completion of treatment (post-treatment).
Plan to share: Yes — The data that support the findings of this study are available from the investigator, TL, upon reasonable request.
Supporting information: Study protocol, Statistical analysis plan, Informed consent form
Time frame: June 2025
Ran from Mar 2024 to primary completion in May 2024, 2 months.
Of 30 interventional studies with no phase under Voice Disorders, half reached primary completion within 37 months of starting (the median), counting those still running; a quarter within 8 and three quarters within 48. This study's 2 months is below that.
How these figures are worked out, and which studies are left out of them.
This study is completed, as verified in Jul 2025. You cannot join it, but the record below documents what was studied.
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