Low Energy Requirement to Sustain Smooth Muscle Contraction. Only 1/10 to 1/300
as much energy is required to sustain the same tension of contraction in smooth muscle as in skeletal
muscle. This, too, is believed to result from the slow attachment and detachment cycling of the cross-
bridges and because only one molecule of ATP is required for each cycle, regardless of its duration.
This sparsity of energy utilization by smooth muscle is exceedingly important to the overall energy
economy of the body because organs such as the intestines, urinary bladder, gallbladder, and other
viscera often maintain tonic muscle contraction almost indefinitely.
