Age-related decline affects fitness and mobility through factors like reduced muscle mass, decreased bone density, and joint stiffness. As individuals age, metabolism slows down, leading to challenges in maintaining strength, flexibility, and overall physical performance. Decreased activity levels further exacerbate this decline, increasing the risk of falls and injuries. Implementing regular strength training, flexibility exercises, and balance activities can mitigate these effects, helping older adults maintain independence and enhance quality of life. Staying active is crucial for promoting longevity and preventing further decline in mobility and fitness.