For me it is a necessary part of my training process, but just an additional element for healthy normal food with enough proteins and carbs. I usually drink vitamins and supplements daily and I do the break in the off-season. What do I prefer: In the morning at least 30 mins before food: Opti-Women by Optimum Nutrition (multivitamins) Folic Acid Omega 3 Iron In the evening 30 mins before bad ZMA Casein In 30 mins after hard training sessions: BCAA Berocca Before running in the morning: L-carnitine I also use sometimes Vitamin D, especially in winter time, but definetly, prefer simple sunlight. Russian mineral water (salty water) is good as well for recovery Couple years ago I did courses of vitamins for heart support, like riboxin and panangin. The article with more details you can find here: https://www.ninazarina.com/post/what-is-about-vitamins

I usually use 4-5 different pairs for training sessions and one racing pair for road. In this season my choice is: 1. Nike ZoomX Vaporfly Next % For a road racing. I have a pink one, The technology is definetly works for me, I feel myself easier and faster in this shoes. I was not lucky to find Alphafly on the stores, but will by them, when Nike starts to sell them to all. 2. Nike Zoom Pegasus Turbo 2 For fast tempo training sessions and intervals. It's perfect lightweight shoes, with a little support under the heel 3. Nike Zoom Fly 3 Good model for training. Can be too warm for summer, but perfect for marathon pace workouts, long distance running and easy recovery runs. 4. Nike Air Zoom Vomero 14 Exactly 14. This is the best version in Vomero series for me. Reliable model for recovery workouts, bad weather and cross country roads. A little bit heavy, but stable. As you can see, I'm running mostly in Nike. It happened about 1 year ago, before that I usually run in Asics and Adidas. I still have a pair of Adidas Adizero Adios (3), but rarely use them. More details about history of my shoes choice you can find here:

It's a very interesting question for me as well, but I've never asked it by myself. I just run, because I can and like to do it

Jack Daniels USATF Distance Initiative Optimizing the Response to Altitude Training 2015 Summary Report