Diastasis Recti Abdominis (DRA) is the separation of the rectus muscles caused by stretching and thinning of the linea alba during pregnancy and childbirth. It's a common condition, affecting 66-100% of women post-birth and can persist for many years, leading to abdominal protrusion, discomfort, and aesthetic concerns. It might also contribute to back pain, urinary issues, and reduced abdominal strength, impacting quality of life. Recent guidelines propose that conservative management, such as rehabilitation interventions, should be prioritized for DRA. However, there is a lack of consensus among researchers regarding the most effective exercise regimen, resulting in diverse rehabilitation programs. Recent evidence advocates not only for closing the gap but also for achieving optimal function. Current studies often neglect to address functional rehabilitation, underscoring the necessity for robust clinical trials, which is the primary focus of this study.

Additionally, although breathing exercises are commonly prescribed for DRA, the precise role of the diaphragm, the primary respiratory muscle, in rehabilitation hasn't been fully examined. The diaphragm forms the upper boundary of the abdominal cavity and plays a key role in the stability of the trunk, working together with the abdominal and pelvic floor muscles. A recent study found reduced diaphragm excursion in postpartum women with lumbopelvic pain during a low postural demanding task, while previous studies suggest that diaphragm training could alleviate such symptoms influencing factors such as diaphragm thickness and excursion, which may be linked to improved trunk stability. Hence, training the diaphragm and accessory inspiratory muscles through Inspiratory Muscle Training (IMT) could potentially play a crucial role in managing DRA.

In summary, the goal of this study is to develop and assess a comprehensive rehabilitation program aimed at effectively reducing DRA and addressing associated dysfunctions. The program will integrate evidence-based rehabilitation interventions, such as trunk stabilization exercises and IMT, targeting all related dysfunctions caused by DRA, and introducing a novel therapeutic protocol not previously implemented. The study will take the form of a prospective, randomized controlled trial (RCT).

The primary objective of the study is to develop and assess a comprehensive rehabilitation program for Diastasis Recti Abdominis (DRA) and associated dysfunctions, through a prospective randomized controlled trial (RCT). The study is aimed at (a) implementing exercise of the superficial and deep abdominal muscles in both concentric and eccentric contractions targeting muscle strength, development, and arrangement of muscle fibers, potentially facilitating the closure of DRA , as well as pelvic floor muscle exercises with adequate loading and progression aiming for optimal muscular adaptations, (b) integrating exercises strengthening the diaphragm and accessory inspiratory muscles (Inspiratory Muscle Training - IMT), to improve diaphragm function (thickness, mobility/excursion) and contribute to the overall optimal function of the trunk, facilitating force transfer through the abdominal wall, especially when combined with exercises tensing the linea alba (transversus abdominis and pelvic floor muscle exercises), (c) progressing simple contraction exercises into functional, according to loading and progression principles for optimal function in static and dynamic conditions, and (d) developing a flexible exercise program that can also be accessed remotely, aiming to enhance women's access to rehabilitation services, potentially enhancing compliance as well.

The study adheres to ethical considerations and the Helsinki Declaration and is approved by the Research Ethics Committee (R.E.C.) of the University of Patras (internal code: 16192/18-12-2023). All participants will be thoroughly informed about the procedure and will be invited to complete the consent form after receiving complete written information about the study and the protection of their data. All patient data will be stored anonymously/coded in a secure cloud platform accessed only by the research team members. Imputation methods will be applied to address situations where variables are missing, uninterpretable, or inconsistent. Any adverse events will be addressed and documented, while medical consultation will be accessible during patient assessment/rehabilitation hours. Any modifications to the study protocol, data collection methods, or other aspects of the study will be reviewed thoroughly among researchers and the Internal Review Board of the R.E.C., and the study protocol as well as study registration will be adjusted accordingly. The accuracy, completeness, and representativeness of registry data is assured by the research team. A comprehensive data dictionary is established among the research team, containing detailed variable descriptions, coding information, and normal ranges, ensuring consistency and clarity in data collection.

Sample recruitment will be through leaflets and posters placed in various areas of the University campus, the University General Hospital of Patras, and the wider region of Achaia, as well as publicizing this research in professional associations (Panhellenic Medical Association, Panhellenic Physiotherapists' Association) and healthcare professionals (obstetricians, gynecologists, urologists, surgeons, etc.) who may encounter such cases. Additionally, informational events will be planned in various areas of Achaia for the general public, and the study will also be promoted on the university website (Department of Physiotherapy webpage), social media, and conferences. Based on the power analysis conducted using GPowerSoftware 3.1.9.7, considering previous studies of good methodological quality and the same primary outcome, a power of 95%, effect size of 0.30, and a significance level of 5% were established. Including an expected dropout rate of up to 20% of the total sample, a total of 48 women are required (39 according to GPowerSoftware plus an additional 20% for possible dropouts). Consequently, each group is estimated to include 16-20 women.

The allocation of participants into different intervention groups (TEG, IMT+TEG, or CG) will be done by a researcher "blinded" to the interventions and assessment methods, using block randomization, creating a sequence of random numbers through specific software. Each participant will be randomly assigned a number from this sequence through a sealed, opaque envelope. Then participants will be randomly allocated to the intervention groups via sealed, opaque envelopes. To ensure homogeneous distribution of the sample among the intervention groups, each block will contain equal number of envelopes for each intervention group. This method ensures both randomization and concealment of allocation, maintaining the integrity and unbiased distribution of the sample. Due to the nature of the treatment, clinicians cannot be "blinded" to the intervention. However, the analysis of the data will be 'blind' (blind assessor). Analysis will be based on data resulting from the initial grouping of patients by treatment protocol (intention-to-treat analysis).

Both assessment and intervention will take place at the Physiotherapy Department of the University of Patras, in the Clinical Physiotherapy and Research Laboratory (CPRlab). Primary outcome measures will be inter-recti distance (IRD), assessed using diagnostic ultrasound (Versana Active™, GE Healthcare, Illinois, US). Secondary outcome measures will include: a) diaphragmatic thickness (inspiratory & expiratory) and excursion measured via diagnostic ultrasound (Versana Active™, GE Healthcare, Illinois, US), b) strength of the inspiratory muscles (measured by MIP, S-Index, PIF) assessed using the POWERbreathe KH2 (HaB International Ltd., Warwickshire, United Kingdom), c) Trunk function, assessed through functional motor control tests including trunk flexion, plank, side plank, McGill's trunk flexor endurance test, and d) specific questionnaires: i) Body Image States Scale (BISS), ii) Activity Assessment Scale (AAS), and iii) Hernia-Related Quality-of-Life Survey (HerQLes). Prior to the study, pilot reliability studies of all assessment tools and feasibility pilot studies will be completed.

Ultrasound measurements will be conducted by two experienced physiotherapists specializing in womens' health and musculoskeletal dysfunctions, who are adequately trained by a radiologist specializing in diagnostic ultrasound and by a fellow physiotherapist who is experienced in using these imaging techniques (Rehabilitative Ultrasound Imaging - RUSI) in daily clinical practice. Both of these healthcare professionals will supervise the assessment procedure and resolve any issues that may arise during the measurements and/or individual analyses. Before the measurements, the examiners will train the participants in diaphragmatic breathing, contraction of deep abdominal muscles (drawing-in maneuver), and pelvic floor muscles (PFM). Women who demonstrate satisfactory control of these muscles will take part in the intervention. Women will also be asked questions regarding their demographics (age, height/weight, etc.), physical condition, and health history. They will subsequently complete the Australian Pelvic Floor Questionnaire (APFQ-GR), which includes questions about bladder and bowel function, sexual health, and potential symptoms related to the pelvic floor. Additionally, they will fill out the International Consultation on Incontinence Questionnaire-Urinary Incontinence Short Form (ICIQ-UI SF-GR). In cases where abdominal wall or lower back pain is reported, patients will be asked to rate the intensity of this pain according to the Numeric Pain Rating Scale (NPRS).

Intervention groups (TEG and IMT+TEG) will follow a comprehensive exercise program that will last 12 weeks and will include the following components: (a) progressive exercises for retraining deep abdominal muscles (transversus abdominis), (b) progressive exercises for retraining pelvic floor muscles, (c) abdominal muscle strengthening exercises (rectus abdominis, obliques), (d) combination of abdominal muscle control and distal extremity movements, and (e) progressive functional exercises. Each session will range from 20 to 45 minutes, with a progressive increase in duration over the weeks. Participants will exercise three times a week, with one or two in-person sessions per 2 weeks at our department's laboratory (CPRlab) under the supervision of experienced physiotherapists, and the rest of the sessions conducted via teleconference, either synchronous or asynchronous. The in-person sessions will occur in small groups of patients and will be supervised by experienced physiotherapists who will adjust or modify exercise progression according to the patients' needs. Teleconference sessions will be conducted via Zoom communications platform (Zoom Video Communications, California, US). Session scheduling, patient communication, and coordination will be facilitated through a blended learning platform (Classroom, Google, California, US), which the research team modified accordingly to present a patient-friendly interface containing useful tools such as leaflets, information, educational videos etc. Exercise compliance will be assessed through exercise diaries uploaded on the platform. If a participant misses a scheduled online session, the exercise session will be recorded and uploaded to the platform. Women will be encouraged to repeat the exercise program as many times as desired during the week, beyond the scheduled sessions supervised by a physiotherapist. Successful completion of the program will require supervised attendance at a minimum of two out of three sessions per week (i.e., >70% attendance). The exercise program's progression will focus on increasing sets, repetitions, exercise complexity, load, and overall program duration. Simple equipment will be used, such as mats, resistance bands, dumbbells, towels, and pillows.

Trunk Exercise and Inspiratory Muscle Training Group (IMT+TEG) will also perform breathing exercises using inspiratory muscle training (IMT) for 12 weeks. Women will perform IMT three times per week. One training session will be in-person (either weekly or 1 in two weeks) using the POWERbreathe Classic IMT (HaB International Ltd.,Warwickshire, United Kingdom) device under the supervision of an experienced physiotherapist. The other two sessions will be conducted via teleconference from home (using the same device) to ensure the adequacy of the training load. Inspiratory muscle exercises will be performed at an intensity of 50-80% of maximum inspiratory pressure (MIP) and will last 5-10 minutes. There will be a total of 3 sets with 8-10 repetitions, performed twice per session. Inspiratory resistance will progressively increase at a rate of 2-3cm H2O per week. Remote IMT sessions will be scheduled before the trunk exercise program to prevent potential patient fatigue.

The control group will not participate in the 12-week exercise program, but will receive a single training session, general information on managing DRA, along with written instructions for proper abdominal and pelvic floor muscle contraction.

Statistical Analysis Data collected will be processed and analyzed using the SPSS program (version 28 for Windows IBM, Armonk, NY, USA). Statistical analysis will identify correlations between the studied variables, and repeated measures ANOVA will be used to identify statistically significant differences among sample groups. Effect sizes with 95% confidence intervals will be calculated for each outcome measure. Effect sizes will be considered large if ≥0.8, moderate if ≥0.5 and small if ≥0.2.

Inclusion Criteria:

• Females aged 18-50 years
• Diagnosed with diastasis recti abdominis (DRA) with an inter-recti distance (IRD) greater than 2.8 cm
• Beyond 6 months postpartum (preferably within the range of up to 5 years postpartum)

Exclusion Criteria:

• Severe chronic respiratory disease (i.e. COPD, chronic bronchitis, pulmonary emphysema or fibrosis)
• Connective tissue disorders
• Neurological disorders
• Severe musculoskeletal conditions hindering exercise participation (e.g., severe low back pain, sciatica, etc.)
• Previous abdominal surgeries (excluding cesarean section)
• Delivery within the last 6 months
• BMI greater than 30 kg/m²