As we age, we inevitably lose muscle mass, with a decline of about 5% every decade, but strength training can help maintain muscle and bone density, thus supporting an active lifestyle. Important indicators of aging include cardio-respiratory fitness, heart pulse, blood glucose levels, and body structure, all of which can be improved with combined strength and aerobic training. Supplements like Niagen have been highlighted as effective in rejuvenating cells and combating the effects of aging.