Final answer:
The assertion that endurance sports tend to burn a higher proportion of fat rather than glycogen during sustained activities is true, as the body relies more on aerobic metabolism and fatty acids for energy in these scenarios.
Step-by-step explanation:
The statement that endurance sports tend to burn a higher proportion of fat is True. During low-intensity activities, such as long-distance running, the body primarily uses aerobic metabolism, which is more efficient and can produce larger amounts of ATP (energy) for sustained activity. Fatty acids are the main source of fuel during these periods because the body has almost unlimited fat reserves, in contrast to the limited stores of glycogen.
The glycogen stores can be depleted, which eventually leads to fatigue, whereas fat reserves can sustain activity for a longer duration. Additionally, individuals with a greater number of slow-twitch muscle fibers, which are more abundant in endurance athletes, have higher endurance levels as these fibers are well-equipped with capillaries, mitochondria, and myoglobin for oxygen delivery and prolonged aerobic activities.