Updated Perspectives on the Role of Biomechanics in COPD: Considerations for the Clinician

Abstract

Patients with chronic obstructive pulmonary disease (COPD) demonstrate extra-pulmonary functional decline such as an increased prevalence of falls. Biomechanics offers insight into functional decline by examining mechanics of abnormal movement patterns. This review discusses biomechanics of functional outcomes, muscle mechanics, and breathing mechanics in patients with COPD as well as future directions and clinical perspectives. Patients with COPD demonstrate changes in their postural sway during quiet standing compared to controls, and these deficits are exacerbated when sensory information (eg, eyes closed) is manipulated. If standing balance is disrupted with a perturbation, patients with COPD are slower to return to baseline and their muscle activity is differential from controls. When walking, patients with COPD appear to adopt a gait pattern that may increase stability (eg, shorter and wider steps, decreased gait speed) in addition to altered gait variability. Biomechanical muscle mechanics (ie, tension, extensibility, elasticity, and irritability) alterations with COPD are not well documented, with relatively few articles investigating these properties. On the other hand, dyssynchronous motion of the abdomen and rib cage while breathing is well documented in patients with COPD. Newer biomechanical technologies have allowed for estimation of regional, compartmental, lung volumes during activity such as exercise, as well as respiratory muscle activation during breathing. Future directions of biomechanical analyses in COPD are trending toward wearable sensors, big data, and cloud computing. Each of these offers unique opportunities as well as challenges. Advanced analytics of sensor data can offer insight into the health of a system by quantifying complexity or fluctuations in patterns of movement, as healthy systems demonstrate flexibility and are thus adaptable to changing conditions. Biomechanics may offer clinical utility in prediction of 30-day readmissions, identifying disease severity, and patient monitoring. Biomechanics is complementary to other assessments, capturing what patients do, as well as their capability.

Keywords: balance; kinematics; kinetics; mechanomyography; postural control; wearables.

Figure 1

Simplified depiction of COPD pathophysiology that leads to biomechanical alterations. Mitochondrial loss/dysfunction, increased circulating inflammatory cells, muscle atrophy, and alterations at the neuromuscular junction contribute to decreased muscle force, rate of force generation, and physical activity, as well as increased muscle fatigue and weakness. These factors, along with many others, contribute to altered biomechanics, decreased exercise capacity, increased physical inactivity, and exercise intolerance. Created with BioRender.com.

Figure 2

Typical biomechanical methods. (A and B) Motion capture represented by cameras systems in the background (solid red circle) record where markers are in space (dotted red circle) and provide information about where the person is in space (kinematics). (C) Force platforms provide information about forces (kinetics). (D) Dynamometers provide information regarding muscle strength and power.