Talk to Pulmonologist / Lung on Tobacco Cigarette Smoking

AoA , its a research based question, I will be grateful if someone answers this. If a certain muscle relaxation technique applied to accessory respiratory muscles significantly improves chest expansion, FEV1 and FVC but no significant difference in their ratio, FEV1/FVC and PEF. What could be the possible reason behind this both ,improvement and no improvement Thanks