From these schedules, two or three typical task periods of about 30–50 % of the whole working time were selected and defined as being representative for the whole work shift. After the measurement, the measuring data of these time periods (“snippets”) were extracted by one of the authors (TG) from the whole measuring data and used as sample files to reconstruct a new working shift by copying and transferring them according to the schedule filled out before (“reconstructed shift”). Thus, we were able to compare the knee-straining postures of the

“measured shift” with the “reconstructed shift” by descriptive and nonparametric statistics. Study sample The validation study was conducted with 14 subjects with a mean age of 35.0 years (SD = 12.5) in three different occupations (eight male service technicians, four male ramp agents, and

two female nursery nurses). Selleckchem Fulvestrant The main study involved a total of 16 different occupations known as professions at risk of developing knee osteoarthritis or other knee pathologies (Coggon et al. 2000; Vingard et al. 1991; Kivimäki et al. 1992; Jensen et al. 2000a; Wickström et al. 1983). From the respective industry sectors, 110 employers were contacted by the German Statutory Accident Insurance and all agreed to participate in the study with 213 male employees FK506 mw from these enterprises volunteering to participate in the measurements. Their mean age Methamphetamine was 35.5 years (SD = 11.3), and all subjects were skilled craftsmen. As 17 subjects participated in more than one measurement, a total of 242 work shifts were analysed (Table 2). Table 2 Occupations with number of subjects (and their average age), work shifts, and task modules in the study Occupation N Age (years) Work shifts (n) Task modules (n) Floor layers 15 43.9 (10.8) 16 4 Installers/plumbers 34 36.6 (13.7) 40 12 Mould makers 4 29.5 (10.3) 4 1 Painters and decorators 18 32.7 (13.2)

19 7 Parquet layers 14 32.1 (9.5) 28 7 Pavers 7 35.6 (4.8) 7 3 Pipe layers 9 37.3 (12.8) 9 4 Ramp agents 8 28.5 (6.6) 8 2 Reinforcing ironworkers 6 33.2 (5.8) 6 2 Roofers 34 34.8 (10.9) 36 14 Screed layers 17 35.7 (10.2) 20 7 Shipyard workers 6 32.5 (7.7) 6 3 Stone layers 15 39.0 (8.7) 15 5 Tilers 19 35.2 (12.2) 20 8 Truck tarp makers 4 37.5 (11.3) 5 1 Welders 3 32.0 (19.1) 3 1 Total 213 35.5 (11.3) 242 81 Values for age are mean values (SD) Statistical analysis The validity of the automatic posture identification in the pretest was confirmed using linear regression and t test for paired samples. For the comparison of the measured and reconstructed work shifts in the validation study, the Wilcoxon signed-rank test (paired samples) and Spearman’s rank correlation coefficient were used.