--- - |2+ Abstract Aims Coupling between walking and breathing in humans is well established. In healthy systems, the ability to couple and uncouple leads to energy economization. It is unknown if physiologic efficiency is susceptible to alteration particularly in individuals with airflow obstruction. The aim of this research to determine if coupling was compromised in a disease characterized by abnormal airflow and dyspnea, and if this was associated with reduced energy efficiency. Methods As a model of airflow obstruction, 17 chronic obstructive pulmonary disease (COPD) patients and 23 control subjects were included and walked on a treadmill for six‐minutes at three speeds (preferred speed and ±20% preferred speed) while energy expenditure, breathing, and walking were recorded. Rating of perceived exertion was recorded at the end of each walking trial. The most commonly used frequency ratio (i.e. strides:breath) and cross recurrence quantification analysis were used to quantify coupling. Linear regression models were used to determine associations. Results Less complex frequency ratios, simpler ratios, (i.e. 1:1 and 3:2) accompanied with stronger coupling were moderately associated with increased energy expenditure in COPD subjects. This was found for all three speeds. Conclusion The novel finding was that increased energy expenditure was associated with stronger and less complex coupling. Increased effort is needed when utilizing a frequency ratio of 1:1 or 3:2. The more stable the coupling, the more effort it takes to walk. In contrast to the complex energy efficient coupling of controls, those with airflow obstruction manifested simpler and stronger coupling associated with reduced energy efficiency. This article is protected by copyright. All rights reserved. - 'Acta Physiologica, Volume 0, Issue ja, -Not available-. '