What fibers in a muscle you need to exercise at low intensity for increasingly longer periods of time?

Slow-twitch muscle fibers (also known as type I fibers) are best exercised at low intensity for increasingly longer periods of time. These fibers are designed for endurance activities and are well-suited to activities such as running, cycling, and swimming. They are characterized by their slow contraction speed, high fatigue resistance, and ability to use oxygen efficiently as a fuel source. When exercising at low intensity, the body primarily recruits slow-twitch fibers to meet the energy demands of the activity. As you continue to exercise at a low intensity for a longer period of time, these fibers adapt and become stronger and more efficient, allowing you to sustain the activity for an even longer duration.