The belt works by applying controlled external pressure around the rib area, so the tightness has a direct effect on how stable the area feels and how comfortably you can breathe. Start with the belt fastened at a comfortable, moderate tension. It should feel like a firm hold, not like a squeezing band. You should be able to take a full breath and talk without extra effort.
One practical approach is to adjust the tension depending on what you are doing. During walking or more active movement, a slightly firmer fit can give more stability. While sitting or resting, loosen the Velcro a little so the pressure is gentler. The Velcro closure is designed for this kind of daily adjustment.
Because chest compression affects breathing mechanics, never overtighten the belt. If you notice shortness of breath, dizziness, pain, tingling, or a feeling that the pressure is too strong, loosen or remove the belt. Use the belt only on the advice of a doctor or physiotherapist, and remove it if breathing becomes difficult. If you are pregnant or have a chronic heart or lung condition, talk to your specialist before using any chest compression product.