The current practice to avoid incisional hernia, one of the most frequent complications following abdominal surgery, is to minimize core muscle activity in the postoperative phase. However, there is no evidence to support the association of core muscle activity and increased incidence of incisional hernia. On the contrary, it is likely that reduced physical activity could lead to physical deconditioning, chronic postsurgical pain (CPSP), and sarcopenia. The investigators will conduct a prospective multicentric randomized clinical trial to compare standard of care to core muscle exercises targeting the abdominal muscles immediately postsurgery. The principle hypothesis is that neither specific exercises of core muscles before and after surgery nor physical restriction alter the incidence of incisional hernias. Secondly the impact of postoperative rehabilitation on CPSP and sarcopenia will be assessed.

The current practice to avoid incisional hernia, one of the most frequent complications following abdominal surgery, is to minimize core muscle activity in the postoperative phase. Therefore the patients are instructed not to bear or lift weights and to limit physical activities in the first 8-12 weeks after surgery. However, there is no evidence to support the association of core muscle activity and increased incidence of incisional hernia. On the contrary, it is likely that reduced physical activity and deconditioning of the core muscles is associated with muscle catabolism, which may lead to physical deconditioning, chronic postsurgical pain (CPSP), and sarcopenia. CPSP is primarily a major burden in terms of reduced quality of life and resource utilization whereas sarcopenia in addition is increasingly recognized as an important independent risk factor for numerous adverse clinical outcomes and mortality.

The investigators will conduct a prospective multicentric randomized clinical trial to compare standard of care to core muscle exercises targeting the abdominal muscles immediately postsurgery. The principle hypothesis is that neither specific exercises of core muscles before and after surgery nor physical restriction alter the incidence of incisional hernias. Secondly the impact of postoperative rehabilitation on CPSP and sarcopenia will be assessed. The patients will be divided into two study arms, one receiving standard of care and the other receiving the intervention. The intervention consists of four specific core muscle exercises to perform daily during the first two months after surgery. Follow-up will be at two, twelve and twenty-four months with clinical examination and ultrasound to detect incisional hernias, assessment chronic postsurgical pain and its treatment and evaluation of muscle mass on CT scans.

Inclusion Criteria:

1. At the University Hospital of Bern, Kantonsspital Solothurn and Olten and BundeswehrZentralkrankenhaus Koblenz:

   • Informed Consent as documented by signature (Appendix Informed Consent Form)
   • Age > 18 years
   • Capable of judgment
   • Undergoing elective or emergency abdominal surgery
   • Laparoscopic or open surgery, midline or transverse incision

2. At the University Hospital of Lausanne:

   • Informed Consent as documented by signature (Appendix Informed Consent Form)
   • Age > 18 years
   • Capable of judgment
   • Undergoing elective open abdominal surgery
   • Midline or transverse incision

Exclusion criteria (in all four participating centres):

• Inability to follow the procedures of the study, e.g. due to language problems, psychological disorders (chronic depression, under antidepressants or neuroleptics), dementia, etc. of the participant
• Enrolment of the investigator, his/her family members, employees and other dependent persons
• Neuromuscular diseases (such as myasthenia gravis or wheelchair-bound patient)
• Preexisting chronic pain disorder, patients under chronic opioid therapy (WHO II and III) or pain modulating drugs (antidepressive medication or antiepileptic medication)
• End-stage disease
• Patients with preexisting abdominal wall mesh, with the exception of inguinal mesh (after inguinal hernia repair)