Multiple clinical trials and studies demonstrate that neuromuscular electrical stimulation (NMES) and related ab shocker devices effectively increase abdominal muscle strength, endurance, and cross-sectional size when compared to controls.
The retrieved papers include multiple randomized trials and studies specifically investigating neuromuscular electrical stimulation (NMES) on the abdominal region. Papers [0], [3], [6], and [9] all provide direct, positive evidence that NMES devices effectively improve abdominal muscle strength, endurance, and hypertrophy. No studies refute the claim.