Effect of tendon vibration on postural control and limb loading during quiet standing in a prosthetic-bypass model

Lower-limb amputation often impairs postural control due to sensory and motor deficits, leading to asymmetrical weight distribution and increased fall risk. Achilles (VAch) and tibialis anterior (VAnt) tendon vibration can induce predictable postural responses through proprioceptive illusions and may offer therapeutic potential for improving balance. However, their effects in individuals with reduced mobility and proprioception, such as prosthetic users, remain unclear. The aim of this preliminary study was to determine whether tendon vibration affects posture in asymptomatic individuals using a prosthetic bypass system simulating a prosthesis and to identify its impact on postural control. We examined the center of pressure (CoP) and its velocity, as well as the weight distribution on the bypass, in 30 healthy participants (sex: 13 (F) / 17 (M), age: 28± 7 (F) / 31± 12 (M) years, body mass: 60± 7 (F) / 73± 11 (M) kg, height: 166± 7 (F) / 182± 7 (M) cm, right dominant leg: 10 (F) / 12 (M)) undergoing vibrations (90 Hz) on VAch and VAnt on the sound limb. We analyzed the effects of vibration on CoP, CoP velocity, and weight distribution, with and without the bypass during the periods before (10 s), during (40 s), and after vibration (10 s). Results showed that the bypass preserved the direction of vibration-induced CoP shifts, but significantly modulated their magnitude, with Achilles tendon vibration producing larger effects when the bypass was worn. Medio-lateral shifts depended on vibration, with VAch (respectively (resp.) VAnt) shifting CoP toward the bypass limb (resp. sound limb), thereby influencing weight distribution. These findings provide preliminary evidence that tendon vibration can modulate postural responses and inter-limb loading in healthy participants using a prosthetic bypass. The results support further investigation of tendon vibration in people with lower-limb amputation, particularly to determine its safety, persistence and potential influence on load distribution.