The goal of this clinical trial is to learn whether lung insufflation capacity (LIC) training can help maintain respiratory function and prolong survival in people with amyotrophic lateral sclerosis (ALS). The main questions it aims to answer are: * Does early and continuous LIC training slow the decline in forced vital capacity (FVC)? * Does LIC training delay the need for tracheostomy or noninvasive ventilation (NIV)? This single-center study at the National Center of Neurology and Psychiatry (NCNP) in Japan will enroll 15 adults with ALS, diagnosed according to the El Escorial or Awaji criteria. Participants will: * Use the LIC Trainer device to perform lung insufflation training twice daily at home * Visit the clinic every 3 months for respiratory and functional assessments * Have lung tests, including FVC, LIC, maximum insufflation capacity (MIC), cough peak flow (CPF), and complete the Amyotrophic Lateral Sclerosis Functional Rating Scale-Revised (ALSFRS-R) There is no control group within this trial; researchers will compare results with matched historical controls from the Pooled Resource Open-Access ALS Clinical Trials (PRO-ACT) database.