Practical recommendations for inspiratory and expiratory muscle testing in LOPD. LLN, lower limit of normal; MEP, maximal expiratory pressure; MIP, maximal inspiratory pressure; PCF, peak cough flow; SNIP, sniff nasal inspiratory pressure; TLC, total lung capacity; VC, vital capacity; PFT, pulmonary function testing; IVC, inspiratory vital capacity; SVC, slow vital capacity; ERV, expiratory reserve volume; IRV inspiratory reserve volume; TV, tidal volume; TLC, total lung capacity; RV, residual volume. Normal values are derived from [33].