Abstract: A garment having differential thermal properties for retaining heat adjacent to the arm and shoulder muscles of an athlete, while allowing the remaining body muscles to naturally cool. The garment comprises a sleeve for covering the arm and a skirt attached to the sleeve for covering the deltoid, pectoral and tarus major and minor muscles adjacent the throwing arm. A coupler is provided for removably attaching the skirt and sleeve to the uniform of the athlete. In a first preferred embodiment this coupler may be a plurality of Velcro patches.