2.1. Subjects

Nineteen healthy subjects (10 men), aged 23-50 (mean, 32) years, with no known neuromuscular or musculoskeletal disorders participated in this study. They were recruited from the university research center population. The Human Ethics Committee of Huashan Hospital, Fudan University, China, granted the ethical committee approval, and each subject gave his/her informed consent prior to the study. Each subject was seated comfortably on a chair, with the left forearm and hand supinated on a solid wooden table with the fingers relaxed and unsupported (Figure 1).

Schematic diagrams illustrating the settings of the experiment with conditioning stimulation of vibration.

Only minimal discomfort was caused by the brief application of vibration to the palm either at metacarpophalangeal joint (MCPJ) of digit 3 or MCPJ of digit 5. No visible venous stasis or color changes on the fingers were observed on any subject.