To study spinal movements during work, an instrument that measured angles and angle changes in relation to a vertical plane was adapted to continuously measure forward flexion of the trunk. The instrument, which is battery-powered and worn on the back, registers the amount of flexion and its distribution over time during a work cycle by recording the time spent in each of five 18.degree. intervals between 0.degree. and 90.degree.. The number of times that the angle of flexion changed from one interval to another is recorded. A total of 43 subjects from 3 occupations (dentistry, nurses'' aide work and warehouse work) were each tested during a 60 min work cycle. On the average, the dentists spent most of the time (52.2 min) in a semi-flexed position not exceeding 36.degree. and performed 8 deep forward flexions (> 73.degree.). The nurses'' aides spent 1/2 of the work cycle (34.4 min) in an upright position (0.degree.-18.degree.) and performed 70 deep forward flexions. The warehouse workers spent < 1/2 of the work cycle in an upright position (27.5 min) and performed 153 deep forward flexions that nearly always were associated with lifting.