The manufacturing details of gym t-shirts can vary depending on the specific brand or manufacturer. However, here are some general steps that are involved in the manufacturing process:

1. Design: The first step in manufacturing gym t-shirts is designing the pattern and style of the shirt. This includes deciding on the fit, fabric type, color, and any logos or designs that will be included on the shirt.
2. Fabric selection: The fabric used for gym t-shirts is typically a moisture-wicking material such as polyester or a blend of polyester and spandex. The fabric is selected based on its quality, weight, and ability to wick away sweat and moisture.
3. Cutting: After the fabric is selected, the fabric is cut into the pattern for the shirt. This is typically done with large cutting machines.
4. Printing or Embroidery: Depending on the design of the gym t-shirt, printing or embroidery may be added to the shirt. This includes adding any logos or designs to the shirt.
5. Sewing: Once the fabric is cut, the pieces are sewn together to create the shirt. This includes sewing the front and back panels together, as well as attaching the sleeves and collar.
6. Finishing: After the shirt is sewn together, it is inspected for quality and any loose threads or other imperfections are trimmed. The shirt is then washed and dried to soften the fabric and remove any manufacturing residue.
7. Final inspection: The final step in the manufacturing process is a final inspection of the shirt to ensure that it meets the quality standards of the manufacturer. The shirt is checked for fit, color consistency, and any defects.
8. Packaging and distribution: The finished shirts are then packaged and shipped to retailers for sale to consumers.

Overall, the manufacturing of gym t-shirts involves a number of steps, including designing the pattern and style, selecting the fabric, cutting the fabric, printing or embroidery, sewing the pieces together, finishing the shirt, and conducting a final inspection before packaging and distribution.