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Ishida H.1, Suehiro T.1, Watanabe S.1
1Kawasaki University of Medical Welfare, Department of Rehabilitation, Faculty of Health Science and Technology, Kurashiki, Japan
Background: Expiratory muscle endurance and strength can be impaired in a variety of populations including sedentary elderly and those with chronic obstructive pulmonary disease, multiple sclerosis, and Parkinson's disease. With the potential to improve swallow, respiration, and physical performance, expiratory muscle strength training (EMST) programs are performed to increase maximum expiratory pressure (PE max). EMST uses a pressure threshold device with a calibrated pressure relief valve housed inside. The threshold pressure used for EMST ranges from 30 % to 75 % of a trainee's PE max. However, little is known about the activities of the expiratory muscles during performing forced expiration. In this study, the rectus abdominis (RA), external oblique (EO), and internal oblique (IO) muscles were selected as powerful muscles of expiration.
Purpose: The aim of this investigation was to quantify the activities of the abdominal muscles during 30 % and 75 % of PE max.
Methods: Fifteen healthy male university students participated in this study (21.1 ± 0.3 years). PE max at total lung capacity was measured using a multi-functional spirometer with an optional respiratory pressure unit. The activities of the RA, EO, and IO muscles were measured using electromyography during 30 % and 75 % of PE max. If the expiratory pressure was more and less than the levels of 5 %, the data was excluded. Data were collected two times for each task. The average EMG values were calculated during the tasks and then normalized relative to maximum voluntary contractions (%MVC). To assess differences among variables, two-way repeated-measures analysis of variance (ANOVA) was utilized. Moreover, when a significant interaction effect was found between main effects, the paired t-test was used to examine the significance of differences between expiratory pressures. For comparison of muscles, one-way ANOVA and post-hoc analysis were performed with the Bonferroni test. Values of p 0.05 were considered statistically significant.
Results: The activities (30 % and 75 % of PE max) of RA, EO, and IO muscles were (6.1 ± 5.7 and 8.1 ± 6.1 %MVC), (11.2 ± 8.5 and 30.6 ± 22.1 %MVC), and (11.8 ± 7.7 and 46.7 ± 33.7 %MVC), respectively. All muscles with 75 % of PE max present significantly higher muscle activity compared to 30 %. The EO and IO muscles showed significantly higher %MVC compared to the RA muscle during 30 % and 75 % of PE max.
Conclusion(s): The activities of all abdominal muscles increased in accordance with the increase in expiratory pressure. Further, there were differences in muscle activity among the abdominal muscles with the same expiratory pressure.
Implications: Muscle endurance and strength induced by expiratory muscle strength training might then be different in each abdominal muscle. Based on the analysis of the study, the findings should be considered when prescribing EMST as a part of a pulmonary rehabilitation program.
Funding acknowledgements: JSPS KAKENHI (15K16383)
Topic: Cardiorespiratory
Ethics approval: This study was approved by the Ethics Committee of the Kawasaki University of Medical Welfare, Japan.
All authors, affiliations and abstracts have been published as submitted.
