Best For Endurance Training: UA RUSH ColdGear Core Top If you're working out in the bitter cold for an extended period of time, this UA RUSH ColdGear Core Top ($75) is your best friend. Not only does it keep you warm with ColdGear fabric, it also uses UA RUSH infrared technology to prevent your muscles from tiring out. Image Source: underarmour.com UA RUSH ColdGear Core Top $75 from underarmour.com Buy Now