i) Do you usually use a sit-stand workstation? Yes/No ii) How long (in month) have you had one? iii) What percentage of day do you use your sit-stand workstation?

JCQ comprises 18 items measuring 5 dimensions related with psychosocial job characteristics: decision latitude, decision authority, psychological job demands, social support and physical job demands.

Range of scores:

• Skill discretion: 12-48
• Decision authority: 12-48
• Phychological job demands: 3-12
• Social Support: 4-16
• Physical demands: 2-8 *Job control = skill discretion + decision authority: 24-96

Dichotomised physical demand and job control are combined to create four categories:

• low strain: low demand and high control
• active job: high demand and high control
• passive job: low demand and low control
• job strain: high demand and low control

Job Satisfaction: comprises 1 question:

"How satisfied are you with your work in general"?

1. extremely dissatisfied
2. very dissatisfied
3. rather dissatisfied
4. more or less satisfied
5. rather satisfied
6. very satisfied
7. extremely satisfied

Questions are about physical activities(PA) (vigorous, moderate, walking) that people do as part of their everyday lives; and about the time they spent being physically active in the last 7-days. Values are computed for walking(W), moderate-intensity-activities(M), vigorous-intensity-activities(V) and a combined total physical activity score. Scores are expressed in MET-minutes/week (METs). The following values are used for the analysis: W=3.3 METs; M=4.0 METs; V=8.0 METs. There are 3 levels of PA proposed to classify populations: Low: individuals who not meet criteria for categories 2 or 3. Moderate: a)3 or more days of V of at least 20 min per day; b)5 or more days of M and/or W of at least 30-min per day; c)5 or more days of any combination of W, M or V achieving a minimum total PA of at least 600-METs. High: a)V on at least 3 days achieving a minimum total PA of at least 1500-METs; b)7 or more days of any combination of W, M or V achieving a minimum total PA of at least 3000-METs.

SF12 questionnaire. This questionnaire ask about the generic health status in 8 domains: physical function, role physical, body pain, general health, vitality, social function, role emotional and mental health. It is a shorter version of SF-36.

Physical and Mental Health Composite Scores (PCS & MCS) are computed using the scores of twelve questions and range from 0 to 100, where a zero score indicates the lowest level of health measured by the scales and 100 indicates the highest level of health. Both Physical and Mental Health Composite Scales combine the 12 items in such a way that they compare to a national norm with a mean score of 50.0 and a standard deviation of 10.0.

A positive score means the person is healthier than average. A negative score means a person is less healthy than average.

An abbreviated version of NMQ is used, which consists of a rear view of the human body, divided into 9 anatomical regions (3 each on the upper limbs, spine and lower limbs), asking about presence of musculoskeletal pain during the last year, the last month and today.

All response options are dichotomous (yes/no). Questions are ordered in such a way that those relating to the respondents' last year are asked first, followed by prevalence questions about last month and today. Key words are highlighted in bold. Respondents are asked to answer all questions for a body region before progressing to the next region (ie, horizontally rather than vertically). If the respondent answer no for question relating to annual prevalence, they are directed to go on to the next body region and all remaining questions for that region are automatically coded as negative responses.

The musculoskeletal intensity in 9 regions, over the previous 7 days, is measured with the VAS.

VAS is a continuous scale comprised of a horizontal line, 10 centimetres (100 mm) in length, anchored by 2 verbal descriptors, one for each symptom extreme: "no pain" (score of 0) and "worst imaginable pain" (score of 100-mm scale).

Oswestry Disability Questionnaire. Lumbar functional disability is measured using this outcome assessment. It contains 10 questions about: pain intensity, personal care, lifting, walking, sitting, standing, sleeping, sex life, social life and traveling. The total score is expressed as a percentage (from 0 to 100). Between 0% and 20% is interpreted as minimal disability; 21% to 40% as moderate disability; 41% to 60% as severe disability; 61% to 80% as crippled; and from 81% to 100% as bed-bound, or exaggerating their symptoms.

Pain Catastrophizing Scale (PCS). This scale consists of 13 statements describing different thoughts and feelings that may be associated with pain. The participant indicate the degree to which they have these thoughts and feeling is it a 5 point scale from "not at all" to "all the time" about the experiences with painful situations.

The flexible ruler, length 60 cm is placed over the spinous processes of the thoracic and lumbar spine so that it follows the contour of the spinal curves, from C7 to the posterior superior iliac spine (PSIS). Spinal processes of the C7 and T12 vertebras, and PSIS are identified and marked. The flexicurve is marked at C7, T12 and S2 level; then it is carefully removed, placed on a stable surface, and the internal edge (the side of the flexicurve in contact with the skin) is traced onto graph paper. Two measurements are obtained from the flexicurve.

a) Active Hip Abduction test: Side-lying position. Participants are instructed to raise their top leg towards the ceiling as far as they can. The side to be tested first is randomized. Examiner score as: 0 = Able to maintain position; 1 = Minimal loss; 2 = Moderate loss; 3 = Severe loss of pelvis position in the frontal plane.

b) Active Straight Leg Raise test (ASLR test): Supine position, with straight legs and feet 20 cm apart. Subject is instructed to raise a straight leg 20 cm above the table. Scoring on a 6-point scale (range 0-5). Scores of both sides are added.

c) Prone Knee Flexion test: Prone position. Instruction is "bend your knee as far as you can without moving your back". Scoring: a) correct: active knee flexion at least 90° without movement of the low back and pelvis; b) incorrect: by the knee flexion low back does not stay neutral maintained but moves in extension or rotation.

Trunk endurance test (McGill´s protocol 1999):

a) Sorensen test: The patient lies on the examining table in the prone position with the upper edge of the iliac crests aligned with the edge of the table. The lower body is fixed to the table by three straps, located around the pelvis, knees, and ankles, respectively.

With the arms folded across the chest, the patient is asked to isometrically maintain the upper body in a horizontal position. The time during which the patient keeps the upper body straight and horizontal is recorded. In patients who experience no difficulty in holding the position, the test is stopped after 240 s.

Trunk endurance test (McGill´s protocol 1999):

b) Abdominal endurance test: This test is performed by having the subject sit on a test bench. Both the knees and hips are flexed at 90° and the feet are fixed to the bench with a strap. The arms crossed over the chest. At the position of 60° trunk flexion, the support of the trunk is then removed and the participant hold the position for as long as possible. The test is terminated when the participant is no longer able to hold the position.

Trunk endurance test (McGill´s protocol 1999):

c) Side bridge test: The side bridge test (right and left side) are performed in the side-lying position on a mat. The participant's knees are extended with the top foot placed in front of the lower foot. The participant supports their weight only on their lower elbow and feet while lifting their hips off the mat. The test is stopped when the side-lying position is lost or when the hips returned to the mat.

Supine Bridge Test:

subject is on the examination table in the supine position, with knees flexed 90 degrees and the soles of the feet on the floor.The hands are positioned by the ears. Subjects are instructed to raise the pelvis from the floor so that the shoulders, hips, and knees are maintained in a straight line. The time is held and timed until the position can no longer be maintained.

Abductor Hip Endurance Test:

in the side-lying position with the evaluated hip placed superiorly in neutral alignment and with the pelvis stabilized by straps. External weight of 7.5% of body mass, is placed on the ankle of the evaluated limb. A inclinometer is strapped 10 cm superior to the lateral femoral condyle. The subject is instructed to isometrically hold the limb in a horizontal position. The time is recorded.