Complex sentence: Aerobic exercise stimulates cortisol secretion in an intensity-dependent manner; however, it does not result in long-term increases in cortisol production since this exercise-induced effect on cortisol is a response to transient negative energy balance.
Split into simpler sentences: Aerobic exercise stimulates cortisol secretion in an intensity-dependent manner. However, exercise does not result in long-term increases in cortisol production since this exercise-induced effect on cortisol is a response to transient negative energy balance.