Effects of Whole-Body Vibration on Lower-Limb Muscle Activity in a Flywheel Half-Squat

Strength and conditioning professionals continuously seek innovative strategies to enhance neuromuscular performance. This study examined muscle activation in the rectus femoris (RF), vastus lateralis (VL), vastus medialis (VM), biceps femoris (BF), gluteus maximus (GMAX), gastrocnemius medialis (GASMED), and gastrocnemius lateralis (GASLAT) during six flywheel squat conditions, with and without superimposed vibration. Thirty physically active participants (15 males and 15 females) performed half-squats (90° knee flexion) on a flywheel device under two inertial loads (IL1 = 0.0306 kg·m² and IL2 = 0.0562 kg·m²), both with and without vibration (30 and 40 Hz). Superimposed vibration elicited muscle- and gender-specific activation increases. In males, the greatest changes occurred in GASLAT (+40.8% eccentric and +55.4% concentric at 40 Hz) and GMAX (+20.1% and +33.8%), whereas other muscles showed modest or inconsistent responses. Females exhibited broader facilitation, with GMAX (+57.2% eccentric and +56.0% concentric) and GASLAT (+73.3% and +80.6%) showing the largest gains, alongside notable increases in BF (+27.9%) and quadriceps (up to +24.7%). These findings indicate vibration at 30-40 Hz substantially amplifies posterior-chain and ankle stabilizer activation, particularly in females, without uniform effects across all muscles. Therefore, combining whole-body vibration with inertial resistance training may optimize neuromuscular recruitment, with potential applications in athletic performance and rehabilitation, especially in females.