The relationship between fitness levels and aging is complex. Generally, as individuals age, physiological changes may contribute to a decline in fitness, including decreased muscle mass, bone density, and cardiovascular function. However, maintaining a regular exercise routine helps mitigate these effects and promotes healthy aging. Active older adults may retain strength, endurance, and flexibility, allowing for better mobility and quality of life. Ultimately, an emphasis on fitness throughout one's life can significantly influence the aging process and enhance longevity.