Something is really bothering me. Obviously Nike is our kit sponsor, but for the gym / fitness work all the players are wearing Adidas Adiboost trainers. What’s that all about
Don't think there's anything in this. Numerous photos of players also in Nike and other branded footwear. Players have deals with various different manufacturers and those deals tend to include wearing that same brand of trainer for fitness/pre-match etc. I'm guessing you've just come across photos of those who have deals with Adidas