Is it possible to have too much of a good thing? Dr. Sanjay Gupta breaks down what research says about long-distance training and neurodegenerative diseases. Plus, he reports on which type of field is safer for young athletes to play on: turf or grass.   This episode was produced by Jesse Remedios.  Showrunner: Amanda Sealy  Medical Writer: Andrea Kane  Senior Producer: Dan Bloom   Technical Director: Dan Dzula  Learn more about your ad choices. Visit podcastchoices.com/adchoices