Safety of core muscle training immediately after abdominal surgery: systematic review

Following abdominal surgery, abdominal wall-healing disorders are common, with up to 6% of patients developing fascial dehiscence (FD) and 35% incisional hernia (IH) within 2 years after high-risk surgery1,2. A widely practised approach to avoid IH is restriction of postoperative activity, including avoidance of fascial strain and elevated intra-abdominal pressure through restriction of core muscle activity. Multiple studies highlight the considerable heterogeneity in instructions given to patients as to which activity can be resumed and when3,4. This resulted in recommendations based on the Delphi method or expert surveys, where avoidance of abdominal wall muscle strain was recommended for 2 weeks after laparoscopic and 4 weeks after open surgery5,6. Yet this is not supported by scientific evidence. In clinical research, there is evidence that coughing, vomiting and standing up, all unavoidable in the early postoperative phase, may generate higher intra-abdominal pressures compared to lifting or core muscle training7,8. The aim of this review was to assess the safety of abdominal (core) muscle physiotherapy in terms of fascial healing, starting immediately after surgery involving an incision of the abdominal wall. The objective was to answer the following question: Does core muscle training immediately after abdominal surgery increase the risk of FD and/or IH? The authors conducted a systematic review according to the Cochrane guidelines and reported the findings according to the PRISMA guidelines9,10. The systematic review was not preregistered. PubMed, CENTRAL and PEDro were searched on 30 September 2023. Studies investigating abdominal wall muscle exercises following abdominal surgery were included, starting on postoperative day one, and reporting on FD and/or IH. Two authors independently assessed inclusion criteria and biases and collected data. Details of the full methods, risk of bias assessment and statistical analysis can be found in the Supplementary material. Two studies were included in the systematic review. Figure S1 details the PRISMA flow diagram of study inclusion, and Fig. S2 presents the risk of bias. Given the limited number of publications, a meta-analysis could not be performed. The characteristics of the two RCTs can be found in Table 111,12. The search yielded no studies that evaluated the safety of core muscle training in terms of FD and/or IH as primary end points. Characteristics of included studies POD, postoperative day. Characteristics of included studies POD, postoperative day. The study population comprised 139 patients. Their characteristics including risk factors for FD or IH are presented in Table S1 and details on patient inclusion are in the Supplementary material. Table 2 presents the physiotherapy conducted in both studies. While the comparator in Ahn et al. was limited to unsupervised mobilization according to the patient’s capabilities11, the control group in De Almeida et al. participated in a programme where core control is listed as a physiotherapy element12. The exact components of core control are unclear and seem to be associated with the determination of core stability, defined as the ability to sit erect for at least 1 min. Nevertheless, it cannot be excluded that core training was also performed by the control group to some extent. Physiotherapy POD, postoperative day; NA, not available. Physiotherapy POD, postoperative day; NA, not available. The exercises’ intensity and the number of repetitions varied according to the patient’s capabilities, variations that were not reported11,12. No statistically significant difference in the occurrence of FD between the intervention and control groups was found, with only one event observed in the intervention group (n = 1/71, P = 0.335). The event was observed on the 28th postoperative day, following a surgical complication, and led to the patient’s death by refractory septic shock12. Ahn et al. reported no FD. The authors found no study assessing the effect of core muscle exercises immediately after surgery on the development of IH. In the included studies, IH was not evaluated as an outcome, and the duration of follow-up would have been too short (30 days)11,12. A subgroup analysis was planned to account for the reported known risk factors for FD (see Table S1), but was not possible due to the low number of events. In Ahn et al., length of stay was significantly shorter in the intervention group than in the control group (P = 0.0005), yet no difference was found in Almeida et al. (P = 0.25)11,12. Further results including complications can be found in the Supplementary material. Even with extended search criteria, the authors found only two publications, none of which was designed with IH or FD as primary end points. Thus, both are underpowered and lack sufficient follow-up time. The available evidence could speak towards the safety of abdominal wall muscle exercises immediately after surgery, as only one FD was reported, but the level of evidence is very low. To assess the effect of physiotherapy on wound healing, findings need to be adjusted to the other known risk factors for FD and/or IH. In these publications, there was a lack of information on co-morbidities, with no significant differences reported, making it impossible to determine whether they played a role in the observed event11,12. Finally, it is unclear if the control group in De Almeida et al. also underwent core muscle exercises. If so, this would again speak towards the safety of such exercises, as no FD was observed in this group12. This study highlights the need for further research in this domain. No evidence was found against core muscle exercises in the immediate postoperative phase, and a limited number of studies investigating this at all, even later in the recovery process13,14. In a similar systematic review on recovery after major abdominal wall repair, only one study was found that included physiotherapy but excluded lifting weights over 2.5 kg for 2 weeks after surgery15,16. In animal studies, time to achieve 50% tensile strength of the rectus fascia after incision ranged from 3 to 8 days17. Generally, fascia healing seemed to be faster than dermis18, and the application of tension to the sutured fascia is thought to be beneficial, as mechanical strain seemed to stimulate fibroblast infiltration and collagen deposition and thus promote healing19. While this has yet to be proven in a clinical setting, it could be central to the promotion of abdominal wall exercises in the immediate postoperative phase. Patients rely on their surgeons and general practitioners to help guide their recovery. Yet as demonstrated by this review, current recommendations are not evidence-based. We must be careful when limiting our patients' physical activity in the postoperative period, as it could have serious consequences in terms of quality of life and deconditioning. This study is limited by the few publications found. Publication bias cannot be excluded, as studies that found core muscle exercises to have negative consequences for the patients in the immediate postoperative phase might not have been published. Finally, the authors are unable to make a statement as to whether these exercises influence the risk of IH, as this specific outcome has never been reported. The available evidence is insufficient to either recommend or discourage core muscle exercise immediately after abdominal surgery. There is currently only one ongoing RCT (NCT0380858420) investigating the effect of core muscle physiotherapy starting immediately after abdominal surgery on IH at 2 years. Based on these results and the results of this systematic review, further studies including co-morbidities for risk stratification and exploring different types and intensity levels of postoperative exercises are needed. Stéphanie Perrodin received funding from the Bangerter-Rhyner Foundation and the Swiss Academy of Medical Sciences for protected research time. Lilian Salm was supported by a Swiss National Science Foundation (SNSF) research fellowship (#P500PM_203210). No other source of funding. The study protocol was not preregistered. The authors declare no conflict of interest. Supplementary material is available at BJS Open online. The data that support the findings of this study are available from the corresponding author upon reasonable request. Stéphanie Perrodin (Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Software, Supervision, Validation, Visualization, Writing—original draft, Writing—review & editing), Lilian Salm (Data curation, Investigation, Methodology, Validation, Writing—review & editing) and Guido Beldi (Conceptualization, Formal analysis, Methodology, Project administration, Resources, Supervision, Validation, Writing—review & editing).

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