Circuit Breathing Exercise on Smoking Cessation Among Youth E-Cigarette Users

Inclusion Criteria: * Male or female aged 15-25 years. * Regular e-cigarette use for at least six months and current e-cigarette use, defined as use on at least one day per week or at least 10 puffs per day during the past 30 days. * Not regularly physically active, defined as exercising fewer than two times per week during the preceding six months. * Able to understand instructions, communicate effectively, and cooperate with the research procedures. * No history of cardiovascular disease or respiratory disease, such as asthma or chronic obstructive pulmonary disease. * No uncontrolled hypertension. Participants with controlled hypertension must have resting blood pressure ≤140/90 mmHg. * Able to move independently without assistance or assistive devices. * Willing to participate and provide informed consent. * For participants younger than 18 years, consent from a parent or legally authorized representative is required. Exclusion Criteria: * Development of an illness, injury, or other circumstance that prevents continued participation. * Withdrawal of consent or unwillingness to continue participation. * Current use of illicit drugs or other tobacco/nicotine products, including conventional cigarettes, shisha/hookah, roll-your-own tobacco, or other nicotine-containing products.