BOWTEX Technical underwear
There is thermal underwear and there is technical underwear. And between those few letters lies a world of difference.
Thermal underwear focuses on breathability and maintaining your body temperature in all conditions: hot, cold, or both.
Technical underwear adds a proverbial layer and abrasion-resistance and/or impact-protection to the story. A proverbial layer, because this is not much thicker - quite the contrary.
Usually, the first difference between 'thermal' and 'technical' is in the materials used and the different qualities and properties they possess. Technical underwear is as good as full-fledged motorcycle clothing when gliding over the asphalt. Thermal underwear will disappear like snow in the sun when you try to do that.