Table 2 Exposure variables (questionnaire) including questions on exposure, answers/options and how the analysis was performed

Personal Characteristics

Age

Trichotomized: 23–37; 38–53; 54–66 years

Height

Trichotomized: 153–163; 164–174; 175–185 cm

Weight

Trichotomized: 45–65, 66–86, 87–107 kg

BMI dichotomized: 17.8–24.9; 25–29.9 kg/m²

Personal Characteristics

Hours/day of personal recovery time [10]

Hardly any time at all; < 1 h/day; 1 h/day; 2 h/day; 3 h/day; ≥4 h/day.

Dichotomized: ≤2; ≥3 h/day

Personal Characteristics

Frequency of physical exercise [10]

Never; Occasionally; Once a week, twice to four times/week; five times/week or more

Dichotomized ≤ once; ≥ twice a week

Personal Characteristics

Hours of household work [10]

0–2; 3–10; 11–20; 21–30; ≥ 31 h/week

Dichotomized: ≤ 10; ≥ 11 h/week

Working conditions

Years as a professional sonographer [8]

Dichotomized at the median ≤ 13 years; > 13 years

Working conditions

Hours of work/week? [8]

Hours of sonography/week? [8]

Hours/week was dichotomized as part-time (< 37 h/week) or full-time work (≥ 37 h/week)

Sonography/week was dichotomized at the median ≤ 18 h/week; > 18 h/week

As these were highly correlated competition was performed including both variables in the same model, and only the factor giving the lowest p-value was included in the main analyses (working hours/week for the neck/shoulders and sonography hours/week for the elbows/hands)

Echocardiography

Do you perform echocardiography?

Yes/no

Dichotomized

Ergonomic conditions during examinations with the ultrasound device

Possibility to adjust

a) screen height

b) screen tilt),

c) the keyboard,

d) the chair

e) table for examinations [8]

Yes/no to all

When positive answer to all items we considered that ergonomic adjustments were possible

Ergonomic conditions during computer work

Satisfaction with the computer work station arrangements? [8]

Very satisfied (can work comfortably); Rather satisfied; Neither satisfied or dissatisfied; Rather dissatisfied; Very dissatisfied (uncomfortable/strenuous work)

Trichotomized: very/rather satisfied; neutral; rather/very dissatisfied

Ergonomic conditions

Performing examinations in the ward on in-patients (bedside examinations)? [8]

Never; Seldom; Sometimes; Daily

Dichotomized: Never/seldom; sometimes/daily

Visual conditions

a. Eyestrain related to computer work? [8]

b. Headache related to computer work? [8]

c. Eyesight adequately corrected? [8]

a and b) Never; Seldom; Sometimes; Often; Very often.

c) Good/adequately corrected; Inadequately corrected

Good visual conditions were considered present if the person had no headaches or eye complaints related to sonography examinations or computer work and sufficiently corrected eyesight

Physical workload

11 items regarding awkward work postures, Mechanical exposure Index (MEI) [11, 12]

Each item answered on a three-point scale Almost not at all; Some; A lot

The total score was calculated for each individual (range 11–33). MEI (sum score) was dichotomized at unexposed/low (≤15) and medium/high exposure (> 15)

Psychosocial conditions

The Job Content Questionnaire was used regarding job demands (nine items), job control (nine items), job support (eight items) [13, 14]

Each item answered on a four-point scale indicating the degree of agreement. Higher values on the scale indicate higher demands, better control and better support.

The mean value in each dimension was calculated for each individual. Each dimension was dichotomized at low/high based on the median value.

Psychosocial conditions

One dimension of The Copenhagen Psychosocial Questionnaire: sensory demands (five items) [15]

Each item was answered on a five-point scale. Higher values indicated higher demands.

The mean value in each dimension was calculated for each individual. The dimension was dichotomized at low/high based on the median value.