Substantial inter-individual variability in sensorimotor incongruence-induced heaviness and null effects of TENS: Implications for experimental paradigm standardization.

Sensorimotor incongruence can induce abnormal limb perceptions such as heaviness, yet effective interventions remain scarce. This study examined whether transcutaneous electrical nerve stimulation (TENS) modulates heaviness induced by sensorimotor incongruence in healthy participants. Seventy-one healthy adults were randomly assigned to a control group (electrodes only), a low-frequency group (4 Hz, 100 μs), a high-frequency group (100 Hz, 100 μs), or a high-pulse-width group (100 Hz, 200 μs). Sensorimotor incongruence was induced via a 250 ms visuomotor delay paradigm. Changes in perceived heaviness were assessed by visual analogue scale and analysed using multiple regression and Bayesian regression with region of practical equivalence (ROPE). Neither stimulation group, psychological components, nor stimulation preference significantly predicted heaviness change (adjusted R² = -0.03, F = 0.55, p = .74); ROPE analysis was indeterminate for all Bayesian coefficients. Model-based clustering revealed that a subset of participants exhibited large perceptual changes, suggesting that future research should identify factors that discriminate responders from non-responders. These findings indicate that TENS does not modulate sensorimotor incongruence-induced heaviness, and highlight that reliable induction of this perception is a prerequisite for intervention research. Paradigm standardization and identification of susceptibility factors warrant future investigation.