You will perspire like no other...these are not breathable at all and the material is not stretchy what so ever.  I cannot wear them to the gym again because I can't even stretch prior to my work-out, let alone run my usual 5 miles in these.  Because they don't stretch as your knees bend during biking, running, elliptical, etc you will get annoyed really fast.  At the same time I bought these on Amazon I also bought Spalding leggings.  The Spalding leggings are what you need to get.  These Adidas would be OK for light workouts outdoor on chilly days (i.e. walking on the trail) but NOT for the gym.