The X-BIONIC® EFFEKTOR® 4.0 trail running shirt supports the athlete with patented thermoregulation and specific trail running functions. Unlike conventional flat compression, the patented X-BIONIC® Partialkompression® exerts pressure via ridges. They improve muscle stability, muscle control and optimize oxygen and nutrient supply. This ensures effective skin cooling. The 3D Bionic Sphere® System with ThermoSyphon® technology provides adaptive thermoregulation. It cools when you sweat and warms when you’re cold. Flexible ExpansionRibs® provide maximum freedom of movement and insulation even when elbows are sharply bent.