Sinusoidal vibrotactile stimulation differentially improves force steadiness depending on contraction intensity.

Studies have reported the benefits of sensory noise in motor performance, but it is not clear if this phenomenon is influenced by muscle contraction intensity. Additionally, most of the studies investigated the role of a stochastic noise on the improvement of motor control and there is no evidence that a sinusoidal vibrotactile stimulation could also enhance motor performance. Eleven participants performed a sensorimotor task while sinusoidal vibrations were applied to the finger skin. The effects of an optimal vibration (OV) on force steadiness were evaluated in different contraction intensities. We assessed the standard deviation (SD) and coefficient of variation (CoV) of force signals. OV significantly decreased force SD irrespective of contraction intensity, but the decrease in force CoV was significantly higher for low-intensity contraction. To the best of our knowledge, our findings are the first evidence that sinusoidal vibrotactile stimulation can enhance force steadiness in a motor task. Also, the significant improvement caused by OV during low-intensity contractions is probably due to the higher sensitivity of the motor system to the synaptic noise. These results add to the current knowledge on the effects of vibrotactile stimulation in motor control and have potential implications for the development of wearable haptic devices. Graphical abstract In this work the effects of a sinusoidal vibrotactile stimulation on force steadiness was investigated. Index finger sensorimotor tasks were performed in three levels of isometric contraction of the FDI muscle: 5, 10 and 15 %MVC. An optimal level of vibration significantly improved force steadiness, but the decrease in force CoV caused by vibration was more pronounced in contractions at 5 %MVC.