If, in singing, the various muscle zones are not well-coordinated and balanced in strength, strain is inevitably put on the breathing system, the spine, the thorax, the throat or the larynx itself, depending on the nature and severity of the imbalance. A reckless combination of imbalance and enthusiasm is evident in the way many singers approach their training or practice, with mindless and often forceful repetition of exercises that have little or no physiological basis or purpose. Negative effects, especially long term ones, are not always immediately discernible. Repeated muscular activity, correct or not, can lead through muscular desensitisation to a feeling of rightness and security.
Harrison, Peter T. The Human Nature of the Singing Voice: Exploring a Sound Basis for Teaching and Learning. Dunedin Academic Press Ltd. 2006.