Ironing can cause shrinkage in some types of fabrics for Fitness Wear, including those commonly used in fitness apparel. The heat and pressure from ironing can cause synthetic fabrics like polyester, nylon, and spandex to shrink, deform, or melt, while cotton and other natural fibers may also shrink or lose their shape.

To avoid shrinkage when ironing fitness apparel, it's important to follow the care label instructions on the garment. Many fitness apparel brands recommend washing the clothes in cold water and air-drying them to prevent shrinkage.

If ironing is necessary, use the lowest heat setting possible and avoid ironing directly over any graphics, logos, or prints on the garment. Instead, iron the garment inside out or place a thin cloth or pressing sheet over the graphic or print to protect it from direct heat.

It's also a good idea to test a small, inconspicuous area of the garment first to see how it reacts to ironing. If you notice any shrinkage or deformation, stop ironing immediately and consider taking the garment to a professional cleaner or tailor for steaming or pressing.

Test standard JIS 1057: Take a sample of 750X750MM and mark points in the longitudinal and latitudinal directions of the sample. The distance between each pair of mark points should be at least 500MM. After balancing for 4H, measure the distance between several pairs of mark points. Use steam with a pressure of 0.4PA and a temperature of 120 degrees to directly iron the test sample back and forth in the longitudinal and latitudinal directions for at least 2 seconds each time, ensuring that each part of the sample is ironed to a minimum. After balancing for 4H, Measure the direct distance between the pairs of marked points after ironing, and calculate the dimensional change rate of the sample. The standard requirement is - 3% - 0%