All the subjects recruited have 4 access to GRAIL, in 4 different day, to test their tolerability to the proposals

The subjects experiment GRAIL virtual reality for three days, during which they deal with 4 different activities.

In the first activity subjects are required to ask over the treadmill in a snow environment.

in the second they are required to stand over the moving platform in a simulation of a boat pitch.

in the third they have to walk over a bridge with a slope. in the fourth the subjects are required to try so interact with virtual reality and to ski between snowman.

if it is possible, on the last day a gait analysis is executed

it is a subjective questionnaire assessing the suitability of the intervention. This is not a health outcome. Indeed SEQ is a questionnaire designed for virtual reality, composed by 13 questions, with a response graded on a 5-point Likert Scale, and a last open question.

It measures measures enjoyment, sense of being in the system, feeling of success and control, realism, easy-to-understand instructions and general discomfort; furthermore it is aimed to detect issues frequently associated with virtual rehabilitation systems, like dizziness or nausea symptoms, eye discomfort, disorientation or confusion symptoms and sense of progress in rehabilitation. Finally, it evaluates the perceived difficulty of the task and the observed difficulty related with the physical interface used in the system.

The gait analysis assessment is conducted over the GRAIL (Gait Real-time Analysis Interactive Lab) system .

It is a laboratory suitable for motion analysis and VR-based rehabilitation. It is composed by a treadmill, provided with two belts that can be driven at different speeds and it is equipped with integrated force platforms. An immersive semicircular screen is placed in front of the treadmill, where VR environments, synchronized with the treadmill movement, are projected. The system uses a Vi-con motion capture system and 3 video cameras to perform motion detection and gait analysis: accordingly, 25 markers were placed on specific anatomical landmarks of the body. Each participant performed a ten-minute familiarization phase and then about 40 steps were acquired.

Spatiotemporal parameters, such as walking velocity, stance duration, stride length and step width, and kinematic parameters of pelvis, hip, knee and ankle were computed.