Effects of handicraft sitting postures on lower trunk muscle fatigue

Fifteen male subjects were exposed to a primary tracking task and a variety of subsidiary tasks for a total of 15 hours. Tracking performance was assessed through the use of two error measures, amount of time off the target track, and number of times off target. Subsidiary performance tasks included: a vigilance task requiring subjects to respond to the deflection of the noodle of a small meter; two reaction time tasks requiring response to the onset of one or the other of two lights; mental multiplication, which required the solution of simple multiplication problems; and digit span, in which the subject was required to repeat as rapidly and as accurately as possible a sot of digits of either five, six or seven numbers in length. In addition, three physiological measures were obtained.

A significant decrement in trucking performance was obtained for both measures utilized. This decrement was not particularly abrupt in its occurrence but rather took place cumulatively over the entire course of the experiment. There was no clearly established performance decrement on the subsidiary tasks utilized in this investigation. A marked variability in performance over the course of the experimental session was characteristic of performance on these tasks. Performance on the vigilance task, and one of the reaction time tasks improved during the 15-hour test session.

The 17-Kotosteroid and 17-Hydroxyeortieoid values increased during the session but only in the case of the latter was the increase significant. The eosinophil count of subjects exposed to the test conditions decreased steadily throughout the experimental session. However, eosinophil measures obtained from control subjects increased during a similar time period.     

Effects of restrictive clothing on lumbar range of motion and trunk muscle activity in young adult worker manual material handling

The objective of this study was to examine the effect of wearing restrictive trousers on lumbar spine movement, trunk muscle activity and low back discomfort (LBD) in simulations of manual material handling (MMH) tasks. Twenty-eight young adults participated in the study performing box lifting, liquid container handling while squatting, and forward reaching while sitting on a task chair when wearing tight pants (sizes too small for the wearer) vs. fit pants (correct size according to anthropometry). Each task was repeated three times and video recordings were used as a basis for measuring lumbar range of motion (LRoM). The response was normalized in terms on baseline hip mobility. Trunk muscle activity of rectus abdominis (RA) and erector spinae (ES) muscles were also measured in each trial and normalized. At the close of each trial, participants rated LBD using a visual analog scale. Results revealed significant effects of both pants and task types on the normalized LRoM, trunk muscle activity and subjective ratings of LBD. The LRoM was higher and trunk muscle (ES) activity was lower for participants when wearing tight pants, as compared to fit pants. Discomfort ratings were significantly higher for tight pants than fit. These results provide guidance for recommendations on work clothing fit in specific types of MMH activities in order to reduce the potential of low-back pain among younger workers in industrial companies.