Final answer:
The false statement about sarcomere shortening is that the length of the I band remains constant during contraction; it actually shortens.
Step-by-step explanation:
The statement about sarcomere shortening that is FALSE is "The length of the I band remains constant." When a sarcomere shortens during muscle contraction, the I band, which contains only thin filaments, actually gets smaller. The A band remains constant in length as it is comprised of the full length of thick filaments, which do not change in length during contraction. The H zone—the central region of the A zone containing only thick filaments—shortens and may almost disappear as the sarcomere contracts. The zone of overlap, where the thin and thick filaments slide past each other, increases as the muscle contracts, which supports the Sliding Filament Model of Contraction.