What occurs during 'thoracic fixation'?

During thoracic fixation, the vocal folds slam shut to prevent air from escaping the lungs. This process is essential in certain activities such as lifting heavy objects, coughing, or during strenuous exertion. By tightly closing the vocal folds, pressure can build up in the thoracic cavity which stabilizes the core and helps provide support for physical activities.

In contrast, the other options describe different functions or actions of the vocal folds that do not specifically pertain to thoracic fixation. For instance, vocal folds becoming taut is related to sound production, while rapidly vibrating vocal folds pertains to voice modulation. Keeping the vocal folds open, on the other hand, is associated with breath control rather than the purpose of thoracic fixation.