The Effect of Adding Supplemental Abdominal Muscle Strengthening to Improve Expiratory Pulmonary Function: A Pilot Study

Purpose: Respiratory muscle training can improve strength, endurance, and ventilatory function. Although the rectus abdominis is considered the primary muscle of forced expiration, limited research has been conducted to explore whether adding external oblique (EO), internal oblique (IO), and transverse abdominis (TA) training could improve key components of exhalation. The purpose of this study was to explore whether the addition of 7 exercises primarily targeting the obliques and TA in trained female athletes would change the expiratory component of pulmonary function. Methods: The participants in this pretest–post-test study were female Division I track and field middle and long-distance runners (n = 22). The participants had 7 exercises added to their in-season training regimen 3 times a week for 8 weeks. Spirometry measured forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), FEV1/FVC ratio, and peak expiratory flow rate (PEFR) before and after the intervention. Surface electromyography was recorded during maximal voluntary contractions of core muscles to monitor desired muscle recruitment and assess pre- and post-training activation levels. Results: The data analysis revealed findings indicating statistical insignificance based on our predetermined confidence interval. However, 3 of the 4 pulmonary function metrics had strong effect sizes. The surface electromyography outputs were lower than the preintervention results and showed no correlation with the pulmonary function results. The spirometry raw data from this study showed that strengthening the EO, IO, and TA muscles can minimally increase the mean difference in aspects of expiratory pulmonary function compared to others. Surface EMG revealed that muscle activity did not improve with low repetition exercises, performed 3 times per week for 8 weeks. The strong effect size for 3 of the 4 tests supports repeating the study with a larger sample size to enhance power and include a control group. In addition, developing an intervention with increased exercise repetitions is necessary to fully appreciate any measurable changes. Conclusion: The introduction of 7 anterolateral abdominal muscle exercises to an established training regimen presented nonstatistically significant increases in FEV1, concomitantly the FEV1/FVC ratio, and PEFR. Observation of the data showed that most participants in 3 of the 4 tests presented with a mean increase in their post-testing effort. Due to the statistical findings and unique traits of the study participants, no clinical links can be extrapolated until further research is conducted.