Effect of somatosensory stimulation of two and three nerves on upper limb function in healthy individuals

Improvement in motor function has been reported in healthy subjects following somatosensory stimulation (SS) of individual upper limb peripheral nerves. This effect could have beneficial applications in rehabilitation, but there is little knowledge of the effects of stimulating multiple upper limb nerves. This study evaluated the effects of SS of two and three nerves on hand function.

A single blind within-group repeated measures design was utilized. Ten healthy subjects (27.1 ± 5.4 years [mean ± SD], three men) were recruited and, after a familiarization session, were given SS to the ipsilateral hand in a randomized order to two (ulnar and median) and three (ulnar, median and radial) nerves on two occasions separated by at least one week. The time required to complete the Jebsen-Taylor Hand Function Test (JTHFT) and handgrip strength of the ipsilateral hand were measured before and immediately after each SS session.

Total JTHFT time decreased significantly by an average of 3.58 ± 2.75 s (9.9%; P = 0.003) and 4.10 ± 3.20 s (11.6%; P = 0.003) following SS to two and three nerves, respectively, but no difference between the two was found. Handgrip strength decreased significantly by 1.82 ± 1.91 kgf (P = 0.015) following SS to three nerves only.

This study suggests that SS of three nerves may facilitate motor training but may also induce a reduction in muscle performance. Further studies are needed to determine the clinical implications of these findings for neurological rehabilitation.