Changes in gait variability and balance control during exertional walking in adults with chronic obstructive pulmonary disease

Background People with Chronic Obstructive Pulmonary Disease (COPD) have high rates of accidental falls. Increased gait variability and poor balance control are known as risk factors for accidental falls in this population. Exertional walking tasks are used in clinical assessments, however changes in gait variability and balance control during exertional walking assessments are not well researched. This study aims to assess changes in gait variability and balance control during and immediately after walking assessments, and the relationship these falls risk factors have with exertion. Methods Participants recruited from a pulmonary rehabilitation program performed two Six-Minute Walk Tests (6MWT) and two Incremental Shuttle Walk Tests (ISWT) one week apart, in a randomised order. Gait variability was measured using a gait sensor mat during the walk tests, and balance control was measured using Functional Reach Test (FR) before and after each walking test. The results were compared using a paired t-test. Concurrently, measures of exertion Rate of Perceived Exertion (RPE), Respiratory Rate (RR), Heart Rate (HR), Peripheral Oxygen Saturation (SpO\(_2\)), and End-Tidal Carbon Dioxide (ETCO\(_2\)) were collected during each walking test. Results Twenty people (17 females, 3 males), aged 71 (±8) years, with Forced Expiratory Volume in one second (FEV1) percent 64 (±18%) of predicted, and Global Initiative for Chronic Obstructive Lung Disease (GOLD) rank 2.2 (±0.75) attended on two occasions. There was no statistically significant change in any of the measures of gait variability analysed from start to end-test in either the 6MWT or the ISWT, despite significant statistical change in RPE (p= .002, p= .007, respectively), HR (p= .010, 0.009, respectively), and SpO\(_2\) (p= .004, p= .034, respectively) for both walk tests, and RR (p= .006) in the 6MWT. Stance time standard deviation had a small but statistically significant inverse association with HR (r= - .143, p= .016) in the 6MWT and a positive association with RPE (r= .133, p= .049) in the ISWT. There were no other statistically significant associations with measures of exertion. There was no statistically significant difference in FR between pre or post reach in the 6MWT (30.08 ±6.15, 29.95 ±5.08 cm, respectively; p= .860), or in the ISWT (30.88 ±5.95 pre-test and 30.23 ±5.51cm post-test, p= .463). Conclusions There was no increase in gait variability despite participants reaching maximum levels of exertion and balance control, as measured by FR test did not change immediately after participating in the walk tests. These results indicate that participating in the 6MWT and ISWT does not degrade gait variability from baseline levels of exertion in a community-dwelling COPD cohort and supports the continued use of either walking test