The primary purpose of this study was to examine the immediate effect of manual stimulation on the foot plant in static and dynamic balance in young healthy subjects. In addition, the secondary objectives of this study were: 1) to identify whether manual stimulation of the foot plant in healthy young subjects, carried out with an easily reproducible protocol with 10 minutes duration, improves static balance, measured with Unipedal Stance Test; 2) to assess whether, manual stimulation of the foot plant in healthy young subjects, carried out with an easily reproducible protocol with 10 minutes duration, improves dynamic balance test, measured with Star Excursion Balance Test.

Methods Participants Participants from the University of Valencia (Spain) were asked to volunteer to participate in this study. Patients were included if they were university students and were able and willing to complete the protocol. Participants were excluded if they were ≥40 years-old or had a known musculoskeletal lower extremity injury (eg, postoperative conditions, musculotendinous or ligamentous problems), previous history of neurological problems, balance disorders (eg, vestibular or visual problems) or did some type of physical activity programme where balance exercises were performed.

Study design We conducted a randomized single-blind controlled study investigation. A non-stratified randomization list was generated and held centrally in sealed envelopes. Therefore, participants were randomly assigned to an experimental group, who received a plantar stimulation on the right foot, or to a control group, which did not receive any intervention.

Intervention Plantar stimulation In addition, a plantar stimulation directed at the plantar surface of the dominant foot was performed by an experienced physiotherapist, as described below. Participants performed one practice trial of plantar stimulation prior to performance. The manipulation was performed with the subject in the supine position. The intervention lasted ten minutes and consisted of four stages: 5 glide pressures focused on each interdigital space and on the internal longitudinal arch of the foot in a caudal direction, that lasted 10 seconds in duration, (2) 5 compression-decompression of each metatarsophalangeal joint, until a slight tension was perceived by the researcher at the joint, (3) 5 glide pressures applied for 5 seconds each, on the region of metatarsal heads, and (4) 5 static pressures applied for 10 seconds each, focused on four points of the sole: the head of the first and the fifth metatarsal head, the heel and the medial side of the midfoot (Figure 3). Duration of pressures was assessed by using an on-line metronome. Furthermore, all pressures, both static and glide, were measured by a strength dynamometer and the mean force of pressure was 48N. After the stimulation, given to the negative effects of the sudden standing-up on several study results, participants stood quietly for 20 seconds before balance tests.

Inclusion Criteria:

• Patients were included if they were healthy university students and were able and willing to complete the protocol

Exclusion Criteria:

• Had a known musculoskeletal lower extremity injury (eg, postoperative conditions, musculotendinous or ligamentous problems).
• Previous history of neurological problems.
• Balance disorders (eg, vestibular or visual problems).
• Did some type of physical activity programme where balance exercises were performed.