Final answer:
The pigment that gives skeletal muscle its reddish-brown color is myoglobin, which is abundant in type-I muscle fibers known for their high oxygen-carrying capacity and endurance.
Step-by-step explanation:
The pigment responsible for the reddish-brown color of skeletal muscle is myoglobin. This protein binds oxygen, allowing muscle tissue to respire aerobically during sustained physical activity. Skeletal muscles contain different types of fibers, and the type-I fibers, also known as slow-twitch or red muscle, are particularly rich in myoglobin, which gives them their characteristic red color.
Type-I muscle fibers are dense with capillaries and are rich in mitochondria and myoglobin, hence supporting aerobic activity and permitting these muscles to sustain long-term contractions. It's contrasted with type-IIb fibers or white muscle, which are less dense in mitochondria and have a paler color due to the lower myoglobin content.
In essence, the striated appearance of skeletal muscle tissue is attributed to the repeating bands of the contractile proteins actin and myosin found in myofibrils, with dark A bands and light I bands contributing to the banded look when observed under a microscope.