Table 1 Experimental protocol differentiated by group (G0, G+, G++).

Baseline

(G0, G+, G++) Participants executed 5 forward bends. The level of the floor was maintained at the same level as the real one. During the last bending, the fingertip-to-floor distance was measured by a tape measure.

Pause

(1 min)

(G0, G+) To standardize the intervention across all groups, participants were asked to wait for one minute in an upright stance position under the fictious pretext that “data needed to be loaded into the system.” During this time, a black dummy loading screen was displayed on the head-mounted display, and the music volume of the virtual scenario was increased.

(G++) Participants were asked to wait in an upright stance position under the fictious pretext that “data needed to be loaded into the system”. During this time, the tile was lifted to match the fingertip-to floor distance reached by the participant during Baseline, and a black dummy loading screen was displayed on the head-mounted display The music volume of the virtual scenario was increased to cover the noise of the moving tile.

Intervention

(G0) Immediately after the pause, participants received a sham manoeuvre accompanied by the following verbal stimulus related to its efficacy:

“Now I am going to apply this tool (digital algometer) on different points of your back after which we will resume the measurement, both with the manual method and with virtual reality.”

Subsequently, participants executed 5 forward bends. The level of the virtual floor was maintained at the same level as the real one.

(G+) Immediately after the pause, participants received a sham manoeuvre accompanied by the following verbal stimulus related to its efficacy:

“Through this manoeuvre, I will treat the main trigger points that reduce the flexibility of the spine and by stimulating them your mobility will increase and you will be able to bend forward more.”

Subsequently, they executed 5 forward bends with the virtual floor maintained at the same level as the real one.

(G++) Immediately after the pause, participants received a sham manoeuvre accompanied by the following verbal stimulus related to its efficacy:

“Through this manoeuvre, I will treat the main trigger points that reduce the flexibility of the spine and by stimulating them your mobility will increase and you will be able to bend forward more.”

Subsequently, participants performed 5 forward bends with the virtual floor raised at the height of the tile lifted in front of the participants.

Pause

(20 s)

(G0, G+) A black dummy loading screen was displayed on the head-mounted display, and the music volume of the virtual scenario was increased.

(G++) A black dummy loading screen was displayed on the head-mounted display, and the music volume of the virtual scenario was increased. The level of the virtual floor was re-settled at the same level as the real one.

After-Effect

(G0, G+, G++) Immediately after the pause, participants performed 5 forward bends. The virtual floor was maintained at the same level as the real one. During the last bending, the fingertip-to-floor distance was measured by a tape measure.

Pause

(5 min)

(G0, G+) Participants were asked to wait five minutes in an upright stance position, before starting the Follow-Up trial. To standardize the intervention across all groups, for the first minute, a black dummy loading screen was displayed on the head-mounted display, and the music volume of the virtual scenario was increased.

(G++) Participants were asked to wait five minutes in an upright stance position, before starting the Follow-Up trial. For the first minute, a black dummy loading screen was displayed on the head-mounted display, and the tile was lowered while the music volume of the virtual scenario was increased.

Follow-Up

(G0, G+, G++) After the pause, participants performed 5 forward bends. The virtual floor was maintained at the same level as the real one. During the last bending, the fingertip-to-floor distance was measured by a tape measure