High prevalence of postoperative ventral hernias necessitates the development of effective rehabilitation protocols to restore abdominal muscle function early and reduce recurrence risk. This study aimed to evaluate the effects of electromyostimulation (EMS) of the anterior abdominal wall muscles on physical activity levels and strength performance in patients after surgical treatment for postoperative ventral hernias. We enrolled 128 patients (mean age, 47.9 ± 8.6 years) who underwent open combined component separation surgery with retromuscular mesh implantation. In the treatment group (n = 64), the course of anterior abdominal wall EMS (enabled by COMPEX SP-2.0) started on the 10^th day after surgery; in the control group (n = 64), we followed a standard post-surgery protocol. The assessed indicators were the level of physical activity (pedometry, 7 days) and the strength of the trunk muscles (strain dynamometry, registered with a BackCheck 700 device). Six months after surgery, the EMS group showed significantly greater muscle strength gains than the control group: in trunk extension, median strength was 26.9 kg versus 15.4 kg (74.7% increase; p < 0.001); in flexion, it was 15.7 kg versus 8.0 kg (96.3% increase; p < 0.001). The level of physical activity in the EMS group was significantly higher: the median number of steps per week was 27304.5 ± 2903.48 (95% CI 20964.6–33644.5), while in the control group it reached 11173.6 ± 3688.8 (95% CI 10065.4–12281.9) steps. This indicates a recovery to 90.0% of the preoperative level. Thus, an early post-surgery course of EMS of the anterior abdominal wall muscles is an effective rehabilitation method that significantly improves the strength characteristics of the core muscles and restores the levels of physical activity in patients.