The below scientific article was conducted at Mayo Clinic in Rochester, one of the best hospitals in the world. It is a good article since the study was a "prospective" and also "randomized" study that was less biased. Therefore, now, we have a proof that exercises change inside our muscle cells.
I do practice Tai Chi a few times a week. Walking or Yoga is also good for aging people. Ancient India and China already knew the health benefits of Yoga and Tai Chi, respectively. https://www.nytimes.com/2017/03/23/well/move/the-best-exercise-for-aging-muscles.html https://www.nytimes.com/2017/03/23/well/move/the-best-exercise-for-aging-muscles.html Cheers, BH Jo
