Effects of whole-body vibration and neuromuscular electrical stimulation on muscle biomechanical properties and thickness in patients in the intensive care unit: a randomized controlled trial

Background: Critically ill patients face a high risk of rapid muscle atrophy and deterioration in muscle biomechanical properties due to prolonged immobilization. Whole body vibration (WBV) and neuromuscular electrical stimulation (NMES) have emerged as adjunctive therapies to preserve muscle structure and function. Objective: This study aimed to compare the effects of WBV and NMES on muscle biomechanical properties and muscle thickness in patients in the intensive care unit (ICU). Methods: Forty-five participants were randomly assigned to groups: WBV plus conventional therapy (CT), NMES plus CT, and CT alone. All groups received 4 weeks of treatment (5 sessions/week). The WBV group received vibration therapy, while the NMES group received electrical stimulation targeting the quadriceps femoris muscles. The control group received CT only, consisting of standard rehabilitation care. Muscle biomechanical properties of the rectus femoris and tibialis anterior muscles, together with muscle thickness of the quadriceps femoris and biceps brachii, were assessed using MyotonPRO and ultrasonography. Results: Whole body vibration produced bilateral increases in muscle tone, stiffness, and elasticity (all p ≤.004), with small-to-moderate effect sizes (η² ≤ 0.12). Neuromuscular electrical stimulation also yielded significant within-group improvements, although these were smaller, whereas the control group showed minimal and mostly non-significant changes. Muscle thickness of the biceps brachii and quadriceps femoris increased significantly in both intervention groups (all p ≤.006). Quadriceps femoris and biceps brachii thickness, rectus femoris tone, and tibialis anterior elasticity exceeded the Smallest Worthwhile Effect, indicating clinical improvements. Quadriceps femoris thickness demonstrated significant time×group interaction effects with large effect sizes (η² = 0.24–0.30), with greater increases observed in the WBV and NMES groups than in the control group. Conclusion: Both interventions enhanced muscle biomechanical properties and muscle thickness, with WBV demonstrating more consistent and pronounced effects. These interventions may offer clinically meaningful benefits for preserving muscle quality and morphology in patients in the ICU. ClinicalTrials.gov: (Identifier: NCT06872697).