Final answer:
Low-intensity, high-duration exercise mainly uses aerobic metabolism with fatty acids as fuel, allowing for prolonged activity. It's efficient for sustaining exercise over time, though glycogen stores can become depleted, leading to fatigue. Adults should aim for 150 to 300 minutes of moderate-intensity exercise weekly, as per the Physical Activity Guidelines.
Step-by-step explanation:
The energy expenditure of low-intensity, high-duration exercise primarily relies on aerobic metabolism, which is efficient at producing ATP by using fatty acids as the main fuel source. Due to the abundance of fat reserves, low-intensity activities such as leisurely climbing stairs, walking, or light cycling can be sustained for extended periods. The body does use a small amount of glucose in conjunction with fatty acids; however, as glycogen stores may get depleted over time, prolonged low-intensity exercise can lead to fatigue. Following the recommendations of the 2018 Physical Activity Guidelines for Americans, adults should engage in 150 to 300 minutes per week of moderate-intensity aerobic activity to reap substantial health benefits, and even more for additional health improvements and weight maintenance.