Final answer:
In early adulthood, physical fitness is at its peak, but as individuals age, there is a gradual decline in physical fitness.
Step-by-step explanation:
In early adulthood, physical fitness is typically at its peak. However, as individuals age, there is a gradual decline in physical fitness. This decline is due to factors such as reduced lean muscle mass and a decrease in metabolic rate. As a result, individuals may experience a decrease in stamina, strength, reflex times, and the senses.