Mitochondria, found in most cells, is where respiration and energy production takes place. As we age mitochondria become impaired and energy production declines. A study sought to determine if high-intensity interval training (HIIT) could reverse that trend.
Two groups did HIIT workouts for 12 weeks - men and women ages 18 to 30 and men and women ages 65 to 80. From this article about the study, High-Intensity Interval Training Helps Slow Down the Aging Process the results: