Final answer:
The greater the level of physical training, the higher the proportion of energy derived from the oxidation of fatty acids during exercise below VO₂max.
Step-by-step explanation:
The greater the level of physical training, the higher the proportion of energy derived from the oxidation of fatty acids during exercise below VO₂max. Aerobic respiration, which takes place in mitochondria, uses glucose, pyruvic acid, and fatty acids as inputs. Fatty acids are the primary energy source during low-intensity activities, and their utilization increases with physical training.