Control of breathing patterns and abdominal muscles during graded loads and

trol of breathing patterns and abdominal muscles during graded loads and tilt. J. Appl. Physiol. 76(6): 2473-2480, 1994.-Tilting from supine to upright purportedly enhances both segmental and pulmonary proprioceptive feedback, whereas an expiratory threshold load (ETL) preferentially en-hances pulmonary feedback. To test this we studied 13 adults when supine and 60 * and 90 * head up. We measured tidal vol-ume, inspiratory duration (TI), and expiratory duration (TE) from flow; estimated end-expiratory lung volume from inspira-tory capacity; and determined burst amplitudes and durations from abdominal electromyograms (EMGs). ETLs were incre-mented from 0 (control) to 25 cmH,O in 5-cmH,O steps. Tidal volume was significantly increased by ETL but was unaffected by body position. Every load prolonged TE, whereas TI re-mained unchanged. When subjects were supine, abdomina