Contractile properties of laryngeal muscles in young and old baboons.

Aging is associated with changes in voice and/or laryngeal protective reflexes in humans. To assess the role of the laryngeal muscles in this change, we have examined in vitro thyroarytenoid (vocalis) muscles excised from the larynxes of young and old baboons. Contractile properties, fatigue characteristics, and resting oxygen consumption of these muscles were measured. The results indicate that the thyroarytenoid muscle of the baboon is a fast muscle that is resistant to fatigue. The thyroarytenoid muscles of older baboons contracted more slowly and recovered less rapidly from fatigue induced by prolonged contractions but developed more maximum active tension than thyroarytenoid muscles of young adult baboons. These small differences in the characteristics of thyroarytenoid muscle of older baboons are probably not sufficient to explain observed changes in laryngeal function in the elderly. The results suggest that changes in neural pathways and/or morphology of the larynx may play a larger role in the altered laryngeal function with age.