Final answer:
During early adulthood (20s to early 40s), physical abilities are at their peak. In middle adulthood (40s to 60s), physical decline begins.
Step-by-step explanation:
During early adulthood (20s to early 40s), our physical abilities are at their peak, including muscle strength, reaction time, sensory abilities, and cardiac functioning. Most professional athletes are at the top of their game during this stage. It is also the stage when fertility is highest in females. However, in middle adulthood (40s to 60s), physical decline begins, with decreases in strength, aerobic performance, vision, and reaction time.