Elsevier

Gait & Posture

Volume 43, January 2016, Pages 101-107
Gait & Posture

Balance recovery is compromised and trunk muscle activity is increased in chronic obstructive pulmonary disease

https://doi.org/10.1016/j.gaitpost.2015.09.004Get rights and content

Highlights

  • Ability to recover balance after postural perturbations is impaired in COPD.

  • People with COPD have greater abdominal muscle activity during postural tasks.

  • Increased trunk muscle activity may limit contribution of the trunk to recovery of balance.

Abstract

Increased respiration in chronic obstructive pulmonary disease (COPD) requires greater abdominal muscle activation, which may impact on contribution of the trunk to postural control. This study aimed to determine whether recovery of balance from postural perturbations and trunk muscle activity differs in people with and without COPD before and/or after exercise. Electromyography (EMG) of the obliquus internus (OI) and externus (OE) abdominis, rectus abdominis (RA), erector spinae (ES) and deltoid muscles was recorded with surface electrodes during rapid shoulder flexion and extension. Time taken to regain baseline centre of pressure velocity (vCOP) and the number of postural adjustments following arm movement was calculated from force plate data. Time to recover balance in the direction of postural disturbance (anteroposterior vCOP) was longer in COPD, particularly more severe COPD, than controls. Mediolateral vCOP (perpendicular to the perturbation) and the number of postural adjustments did not differ between groups, but people with more severe COPD were less successful at returning their mediolateral vCOP to baseline. Abdominal muscle EMG was similar between groups, but controls had greater ES EMG during arm movements. Individuals with more severe COPD had greater OE and RA EMG both before and during arm movement compared to those with less severe COPD and controls. Following exercise, OE and ES EMG increased in people with less severe COPD. This study shows that severe COPD is associated with impaired ability to recover balance and greater trunk muscle activity during postural challenges. Augmented trunk muscle activity may limit the contribution of trunk movements to balance recovery and could contribute to increased falls risk.

Introduction

Chronic obstructive pulmonary disease (COPD) has non-respiratory consequences, including impairments of muscle strength/endurance [1], [2] and balance [3], [4], which may increase risk of falling. The mechanisms underlying impaired balance in COPD are poorly understood; however, mediolateral (ML) balance control appears more impaired than anteroposterior (AP) control [4]. In quiet stance, ML balance depends on hip and trunk moments/movements, whereas AP balance is controlled by ankle moments/movements [5], [6]. One plausible explanation for ML balance compromise in COPD is reduced contribution of trunk muscles/moments to balance secondary to increased respiratory demand.

Excessive trunk muscle activity can compromise trunk movement, and reduced movement can compromise balance [7]. When respiratory demand is increased in individuals without disease by breathing with hypercapnoea, abdominal muscle activity to regain balance during unexpected surface translation [8] and lifting [9] is increased. Similar augmentation of trunk muscle activity in COPD might compromise balance. Evaluation of postural adjustments associated with arm movements tests both postural activity of trunk muscles [10] and balance recovery [11]. This study aimed to test the hypotheses that; balance recovery after postural disturbance would be compromised in COPD; and this would be accompanied by excessive trunk muscle activity secondary to the dual role of trunk muscles in respiration and posture.

Section snippets

Participants

Fifteen individuals with COPD and fifteen volunteers without respiratory disease matched for gender (9 males and 6 females/group), age (independent t-tests; p = 0.63), body mass index (p = 0.94) and activity level [12] (p = 0.10) participated (Table 1). Individuals with stable COPD were included if they had: forced expiratory volume in one second (FEV1) <50% predicted [13], <25% change in FEV1 after bronchodilation (to exclude asthma); and did not require home oxygen. Volunteers without respiratory

Respiratory variables

Respiratory rate was greater in participants with COPD than without, both before and after exercise (main effect group: p = 0.004, interaction Group × Exercise: p = 0.019, post-hoc: p < 0.023). Tidal volume did not differ between groups pre-exercise (0.94 (0.33) L vs. 0.95 (0.26) L; p = 0.18), but participants with COPD had greater tidal volume post-exercise (1.41 (1.15) L vs. 0.82 (0.20) L; p = 0.023). Mean post-exercise breathlessness was reported as 3.3/10 (1.6) by participants with COPD (“moderate”

Discussion

Results show compromised balance recovery in COPD which was accompanied by greater trunk muscle activity (above that required for breathing) associated with a simple balance perturbation. People with more severe COPD had greater OE and RA activity during breathing at rest (before arm movement) and when respiratory and postural demands were combined (after arm movement onset), and people with less severe COPD had increased OE and ES EMG following exercise. The congruence of observations of

Conclusion

This study identified that people with COPD have increased superficial abdominal muscle activity during postural tasks, and impaired ability to recover balance after postural perturbations. Trunk stiffness secondary to increased trunk muscle activity may limit the contribution of the trunk to the recovery and maintenance of balance; thus, increasing risk of falls. Further research is warranted to investigate the effect of reduction of trunk muscle activity on balance control, and the

Conflict of interest statement

None of the authors have any potential conflicts of interest to declare.

Acknowledgements

This research was supported by participants from the 50+ Registry of the Australasian Centre on Ageing at The University of Queensland. We thank Helen Seale and James Walsh from the Prince Charles Hospital for their assistance with subject recruitment. The study was funded by a Program Grant (ID631717) from the National Health and Medical Research Council (NHMRC) of Australia. PH is supported by a Senior Principal Research Fellowship (APP1002190) from the NHMRC. The study sponsors had no role

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