The Slim Fit T-shirt is an excellent choice if you have shoulder and back problems. Our T-Shirt provides soothing Far Infrared(FIR) therapy that’s particularly helpful for shoulder and upper back discomfort. How do we accomplish this? With Back on Track® ’s specially designed fabric called Welltex®, a blend of bio mineral powders melted into the threads. How does Far Infrared (FIR) Therapy help? FIR wavelengths have relatively high penetrability up to 1.5 inches beneath the skin deep into tissue and induce a higher skin blood ?ow in most biological materials. In this point, FIR can penetrate through the skin into subcutaneous tissue that induces the generation of heat energy through its resonance effects. That stimulates intramolecular micro-vibrations to invigorate cellular activities through expanding capillaries and increase the circulation of nutrient-rich, oxygenated blood, thus improving overall metabolism. FIR also regenerates tissues and activates the immune system and enhances the removal of cellular waste materials. https://botcanada.com/ Sizing charts can be found https://botcanada.com/sizing-charts/