Fitness varies significantly between different age groups due to physiological changes and varying energy levels. Younger individuals often experience higher metabolic rates and muscle mass, allowing for greater physical capacities. As people age, they face muscle decline and potential joint issues, leading to modified exercise approaches focusing more on flexibility and strength training. Older adults may benefit from low-impact activities to promote cardiovascular health while minimizing injury risks. Emphasizing appropriate exercise regimens based on age and ability is essential for maintaining optimal fitness throughout the lifespan.