Diastasis Recti Abdominis (DRA) is a common condition experienced postpartum, in which the abdominal muscles separate along the midline of the abdomen due to stretching and thinning of the linea alba. It's a common condition, affecting 66-100% of women post-birth and may be associated with changes in abdominal support, posture, breathing, and trunk function. Although DRA primarily affects the muscles of the abdominal wall, it is speculated that other muscles controlling and stabilizing the trunk, such as the pelvic floor muscles or the diaphragm, might be affected as well. Currently, several studies have investigated the possible negative effects of DRA on pelvic floor function. However, little is known about how it may be related to diaphragm function and accessory breathing muscles.

The purpose of this observational study is to compare diaphragm characteristics and function, and accessory breathing muscle strength in women who have given birth, with and without DRA.

To make this possible, adult parous women from the broader Achaia region are assessed and allocated into two predefined groups based on the presence or absence of DRA. Participants undergo a single assessment session including rehabilitative ultrasound imaging (RUSI) of the diaphragm and standardized tests of inspiratory muscle strength. Additional demographic and clinical information related to pregnancy and physical activity is also recorded. The main hypothesis of this study is that women with DRA demonstrate altered diaphragm function, as well as reduced inspiratory muscle strength, compared to women without DRA. The study aims to improve understanding of the possible relationship between DRA and breathing function after childbirth and to support future research and rehabilitation approaches for women with the condition.

Diastasis recti abdominis (DRA) is a common postpartum condition, characterized by stretching and thinning of the linea alba and separation of the two rectus abdominis muscles along the midline of the abdomen. Beyond cosmetic concerns, DRA has been associated with impaired abdominal wall function, altered trunk stability, and potential changes in respiratory mechanics due to the close anatomical and functional relationship between the abdominal muscles and the diaphragm.

The diaphragm plays a central role in respiration and trunk stabilization, working synergistically with the abdominal wall to regulate intra-abdominal pressure (IAP) and postural control. Alterations in abdominal wall integrity, such as those observed in DRA, may therefore influence diaphragm function and mobility, as well as overall respiratory muscle performance. However, evidence regarding the relationship between DRA and diaphragm function currently remains limited.

This observational, cross-sectional study aims to examine diaphragm characteristics and inspiratory muscle strength in parous women with and without DRA. Participants are allocated into two predefined groups according to the presence or absence of DRA, based on a standardized imaging assessment.

Diaphragm function is assessed using rehabilitative ultrasound imaging (RUSI) techniques, performed by a trained physiotherapist, following standardized procedures. Ultrasound images are obtained during specific breathing maneuvers to determine diaphragm thickness and excursion. Inspiratory muscle strength is assessed using a standardized procedure to test maximal inspiratory pressure (MIP), S-Index and Peak Inspiratory Pressure (PIF) using a POWERbreathe KH2 device. All measurements are conducted during a single assessment session, and are led by three experienced physiotherapists. Furthermore, demographic data and relevant obstetric and clinical characteristics, such as age, body mass index (BMI), parity, and time since last delivery, are recorded to describe the study population.

The study aims to explore whether women with DRA demonstrate differences in diaphragm-related parameters and inspiratory muscle strength compared with women without DRA. By improving understanding of the interaction between the abdominal wall and respiratory muscles after childbirth, this research may contribute to the development of more targeted assessment strategies and rehabilitation approaches in postpartum care.

Inclusion Criteria:

• Female sex
• Aged 18 to 50 years
• Parous women (at least one previous childbirth)
• At least 6 months postpartum at the time of assessment (and within 5 years postpartum)
• Ability to understand and communicate in Greek
• Willingness to participate and provide informed consent

Exclusion Criteria:

• Current pregnancy
• Delivery within the previous 6 months
• History of severe chronic respiratory disease (e.g., chronic obstructive pulmonary disease, chronic bronchitis, pulmonary emphysema, pulmonary fibrosis)
• Presence of connective tissue disorders
• Presence of neurological disorders
• Severe musculoskeletal conditions that could affect trunk or respiratory function or limit participation in testing procedures (severe low back pain, sciatica etc.)
• Previous abdominal surgery, with the exception of cesarean section

Parous adult women from the local community (broader Achaia region) recruited through invitations and referrals and assessed in a clinical research setting.