The abdominal muscles can actually contribute to inspiration by:

a. contracting at end-exhalation.
b. contracting at end-inhalation.
c. causing a cough.
d. increasing end-inspiratory lung volume.

ANS: A
The abdominals can also contribute to inspiration by contracting at end-exhalation. This reduces end-expiratory lung volume, so the chest wall can recoil outward, assisting the next inspiratory effort.