Causes of Vocal Fatigue by David Jones (2001) VoiceTeacher.com.
Causes:
(1) Smoking or drinking alcoholic beverages.
(2) Belting: using too much chest voice pushed up to high in the scale.
(3) Using a technique with a tight solar plexus during singing.
(4) Singing with a high larynx.
(5) Singing with a low soft palate.
(6) Singing with a forward jaw position.
(7) Singing with the vocal cords too far apart or too squeezed together.
(8) Pushing too much breath pressure through the larynx.
(9) Incorrect posture; dropped chest or hyper-extended chest.
(10) Singing with the head posture pushed forward from the spine.
(11) Use of mouth vowels instead of pharyngeal vowels.
(12) Unsupported singing; lack of connection to the resistance of breath pressure in the lower back and abdominal muscles.