Genesis Hernandez-Vizcarrondo, Matthew J. Fogarty, Humzah Abdulkader, Lucy Sieck, Carlos B. Mantilla, Gary C. Sieck
Aging selectively impacts the function of type IIx/IIb fibers in the diaphragm muscle. We show that sarcopenia reduces maximum specific force, maximum shortening velocity, and peak power output, whereas endurance during repetitive contractions is preserved. These findings explain why higher force airway clearance behaviors decline with age, whereas fatigue-resistant breathing behavior remains resilient.