Which event does not happen during muscle contraction ?Actin filaments move towards H-zone Decreased length of myosin filament Decreased length of sarcomereLength of A-band remains unchanged.

During muscle contraction, several events occur. Let's analyze each option to determine which event does not happen.

1. Actin filaments move towards the H-zone: This is a correct event that occurs during muscle contraction. Actin filaments slide towards the center of the sarcomere, causing the H-zone to decrease in size.

2. Decreased length of myosin filament: This is also a correct event that occurs during muscle contraction. The myosin filaments pull the actin filaments towards the center of the sarcomere, resulting in a decrease in the length of the myosin filament.

3. Decreased length of sarcomere: This is another correct event that occurs during muscle contraction. As the actin and myosin filaments slide past each other, the sarcomere shortens, leading to a decrease in the length of the sarcomere.

4. Length of A-band remains unchanged: This is the event that does not happen during muscle contraction. The A-band, which represents the length of the myosin filament, actually remains unchanged during muscle contraction. It is the I-band and H-zone that decrease in size, while the A-band remains constant.

Therefore, the event that does not happen during muscle contraction is that the length of the A-band remains unchanged.