Final answer:
The I band in the sarcomere always contains thin filaments and no myosin overlap.
Step-by-step explanation:
The region of the sarcomere that always contains thin filaments with no myosin overlap is known as the I band. This band consists solely of actin filaments and shortens during muscle contraction. The I band is distinct from the A band, which does encompass regions with overlapping actin and myosin filaments, and the H zone, which only contains myosin filaments. Understanding the structure and behavior of the sarcomere is vital for comprehending how muscles contract, as the sliding of the thin filaments past the thick filaments leads to shortening of the muscle fiber and generates tension.