The Reactor Jacket from Under Armour is an insulated jacket you can actually work out in. The insulation adapts to your activity level, so as you heat up, it lets out warmth.

• ColdGear Reactor intelligent insulation adapts to any activity for non-stop comfort & total versatility
• Lofty insulation with quilting that traps heat, but still allows air to flow so you don't overheat
• Shell: 100% Polyester/Lining: 100% Nylon/Insulation: 100% Polyester
• Smooth, ripstop woven fabric is lightweight and extremely durable
• Generous funnel neck collar for added coverage and comfort