Which type of muscle fibers are primarily used in low-intensity activities?

Slow twitch muscle fibers are primarily used in low-intensity activities due to their characteristics that favor endurance and sustained activity rather than quick bursts of power. These fibers, also known as Type I fibers, have a high density of mitochondria, which allows them to utilize oxygen effectively for aerobic metabolism. This makes them particularly well-suited for activities such as distance running, cycling, or any activity performed over an extended period where stamina is more critical than speed.

Their slow contraction speed and lower force output enable them to resist fatigue, making them ideal for prolonged physical activities where the energy demand is lower but sustained. In contrast, fast twitch muscle fibers are more suited for high-intensity, explosive movements, while intermediate fibers have characteristics of both but are not specifically focused on low-intensity tasks. Cardiac muscle fibers, on the other hand, are specialized for the heart's function and do not directly relate to skeletal muscle activities.