Correlation between peak expiratory flow and abdominal muscle activity in elderly women while holding maximum expiration and performing the side bridge exercise.

Introduction: Expiratory flow is important to minimize the risk of infection by expelling foreign substances from the lungs. Abdominal muscle activities primarily produce expiratory flow. However, data on the association of abdominal muscle activity during expiratory effort and abdominal exercise posture with expiratory flow rate is limited. This study aimed to assess the correlation between expiratory flow and abdominal muscle activity while holding maximum expiration and performing the side bridge exercise in elderly women.

Methods: Rectus abdominis (RA), external oblique (EO), and internal oblique (IO) muscle activity was measured using electromyography in 14 elderly women (82.8 ± 6.7 years), who could walk independently while performing 2 tasks: holding their breath after maximum expiration in the crook-lying position (maximum expiration), and performing the side bridge exercise on their knees without breathing instruction (side bridge). Peak expiratory flow (PEF) was obtained using a peak flow meter. Correlations between PEF and the abdominal muscle activity were determined using the Spearman rank correlation coefficient.

Results: The correlation coefficients between PEF and RA, EO, and IO activity while holding maximum expiration were 0.407 (p = 0.149), -0.345 (p = 0.227), and 0.732 (p = 0.003), respectively. The correlation coefficients between PEF and RA, EO, and IO activity while performing the side bridge exercise were -0.297 (p = 0.303), -0.552 (p = 0.041), and 0.147 (p = 0.615), respectively.

Conclusions: Higher IO activity while holding maximum expiration or lower EO activity while performing the side bridge exercise was related to higher PEF. Thus, maximum expiration and abdominal exercise might be effective in the improvement or prevention of the decrease of expiratory flow.