Shallow, fast chest breathing can cause the neck and shoulder muscles to activate unnecessarily — because in this breathing pattern, the neck muscles try to assist respiration. Diaphragmatic breathing (deep breathing where the belly expands and the chest stays calm) reduces this unnecessary muscle activation and lowers overall tension. A simple practice: inhale through your nose for 4 seconds, feel your belly rise, exhale slowly through your mouth for 6 seconds. Doing this for a few minutes before exercise, or during a stressful moment in the day, can noticeably reduce tension in the neck and shoulders.