Quantifying the dynamics that link leg tendon vibration to induced periodic postural oscillations in young subjects

Periodic sensory perturbations in humans have provided insights into postural control in health and disease. However, the contribution of sinusoidal proprioceptive drive and its interaction with haptic cues has not been systematically explored. Here, a bilateral Achilles tendon\u2013vibration paradigm, using a 100 Hz sinusoidal carrier amplitude-modulated (AM) by sinusoids at 0.1\u20130.5 Hz, was applied to 16 healthy young adults. Anteroposterior center-of-mass (COM) displacement was analyzed. There was an entrainment between the envelope signal and the COM, visible as narrow peaks in the power spectrum superimposed on the broadband sway background. Magnitude-squared coherence was significant at the modulation frequencies, and spectral gain was higher at lower modulation frequencies, indicating effective low-frequency proprioceptive drive on postural sway. An increasing phase lag with frequency was observed between the envelope of the stimulation and the COM at the modulation frequencies. When fingertip light touch on a fixed surface provided a haptic cue, sway power at the modulation frequencies decreased by 8\u201313 dB, coherence was reduced, spectral gain decreased by 7\u201314 dB, and the phase\u2013frequency relation deviated from the linear pattern observed without light touch. Light touch weakens vibration-induced input\u2013output coupling and reshapes the phase\u2013frequency relation. These findings identify amplitude-modulated tendon vibration as a selective proprioceptive probe of postural dynamics. All experimental data are openly available in a public repository, providing a resource that may facilitate cross-cohort comparisons, support the development of future diagnostic methodologies, and contribute both to the evaluation of rehabilitation interventions and to the incremental development and validation of computational models.