Runner's Training Tips: training in flats

There a few categories for flats.

1.) light weight trainers (9-10 oz). I use these a couple times a week for regular training runs and also for easy tempos. I like my Mizuno Wave Precisions and New Balance 825s for these type of shoes.

2.) 'heavy' flats (5.5-9 oz). Stuff like this would probably best be used for interval training on the track. Using it for anything else would probably cause some issues. For me, Brooks T4s and Mizuno Wave Ronins.

3.) feather light racers (less than 5.5 oz). For me, I only use these types of flats during races because they are less resilient than the more substantial flats and typically only last ~100 miles. My personal examples are Adidas Adizero PR and Mizuno Wave Universe.

These categories aren't necessarily static. I wouldn't recommend an Adizero PR (3.9 oz) to someone who weighs 215 lbs. That is probably going to cause comfort issues for the person and durability issues for the shoe. In a case like that, perhaps the 'heavy' flats category of shoes would be their race only type of shoes and light weight trainers could be their speed training shoes. I think you get the point.

That said, I don't think training in flats every day is a good idea, especially if you have overpronation issues. The vast majority of flats do not have any built in medial posting (there are exceptions however), which is going to cause other issues if you need correction from your running shoes. Flats definitely have their uses within training, but my advice is to use them sparingly (in the cases described above).

flats = lightweight shoes used primarily for racing, but also occasionally for training (see my previous post for more specific examples)

overpronation = too much inward ankle movement or an inordinate amount of stress being placed on your arch when you run (or walk) 

medial posting = high density foam (or a rigid wave plate from Mizuno) that is put into shoes to correct overpronation