The goal of this cross-sectional study is to evaluate the immediate effect of heels elevation on the spine posture in a group of 100 healthy subjects (50 males, 50 females). The main question it aims to answer is weather high heels immediately affects spinal posture and pelvic position in the sagittal plane.

Participants will undergo an elevation of 3cm and then 7cm of both heels, while their spine posture will be examined by means of a rasterstereography device.

The data collected by the rasterstereography device will be:

1. pelvic tilt angle (PI), the angle determined by the vertical and the tangent to lumbosacral junction (ILS);
2. ITL-ILS lordotic angle, measured between the tangents of the thoracolumbar junction (ITL) and the lumbosacral junction (ILS);
3. ICT-ITL kyphotic angle, measured between the tangents of the cervicothoracic junction (ICT) and the thoracolumbar junction (ITL); see fig. 1;
4. lumbar arrow (FL) horizontal distance in millimeters from the vertical line that passes through the kyphotic apex in the lumbar spine;
5. cervical arrow (FC) (horizontal distance in millimeters from the virtual vertical plumb line that passes through the kyphotic apex in the cervical spine);
6. antero-posterior flexion of the trunk (Trunk Inclination-TI) measured as the angle between the vertical line and the line passing through the prominent cervical vertebra (VP) to the line connecting the two dimples (DM); see fig. 2.

Participants will provide information on age, height and weight. A questionnaire will be administered to standardize the types of high-heeled shoes used and to verify their frequency of use.

Evaluation Protocol

1. sample 1: barefoot neutral position;
2. sample 2: barefoot neutral position;
3. sample 3: 3 cm rise under both heels;
4. sample 4: 7 cm rise under both heels.

The positioning with respect to the measurement system will be carried out according to the indications provided by the supplier.

To standardize the position subjects will be prepared for analysis as follows:

1. standing, back to the detection system, in a relaxed posture with the knees fully extended with bare feet on the floor (neutral position);
2. bare trunk with pants and briefs lowered to half of the glutei
3. in the case of long hair, it will be required to tie it with suitable means (cap, hair clips, hair bands, etc.) so that the neck is visible up to the hairline;
4. rings, watches and necklaces will be removed to avoid any interference with light lines (necklaces in particular increase this probability).

In the third survey, the heel will be raised by inserting a plastic bar symmetrically under both heels, as proposed in previous studies in which wood was used, by 3 cm; for the fourth evaluation it will be 7 cm.

After the first evaluation in the neutral position, before the evaluation with the heel lift, a second evaluation will be performed under the same conditions to evaluate the reproducibility of the data. The time between the two assessments will be less than 1 minute and the subject will not change position.

Inclusion Criteria:

All healthy subjects.

Exclusion Criteria:

• structural or neurological abnormalities that would prevent standing for 5 seconds with their heels on a 7 cm high plinth;
• regular users of shoes with 7 cm high heels (or more), with a frequency of more than twice a week and / or more than 3 hours / week;
• low back pain in the past 30 days.