The effects of decreased inspiratory capacity on postural stability during backward reach

[Purpose] The purpose of this study is to investigate the effect of decreased inspiratory capacity on the backward reach distance in healthy young individuals, as patients with chronic obstructive pulmonary disease have a high risk of falling. [Participants and Methods] Thirteen healthy volunteers (age, 19.2 ± 0.4 years: mean ± SD) participated in this study. We recorded the backward reach distance at the resting expiration level and at two different inspiratory capacity levels: −1/3 and −2/3 of inspiratory capacity, when the air is inhaled at resting expiration level. We assessed the backward reach distance for each inspiratory capacity, using one-way repeated measures analysis of variance and post-hoc analysis. [Results] We found that inspiratory capacity has a significant effect on backward reach distance. The backward reach distance was significantly decreased in participants with a −2/3 inspiratory capacity, compared with the backward reach distance in participants with a resting expiration level. [Conclusion] Patients with lung volume fractionation and decreased inspiratory capacity lack postural stability during backward reach. Therefore, the link between decreased inspiratory capacity and loss of balance in patients with chronic obstructive pulmonary disease may, in part, be due to decreased postural stability, and the resulting tendency to plan movements, which create a loss of balance.