Fatigue Caused by Visual Display Terminal Work : An Experimental Investigation

Experiments were carried out to examine fatigue during VDT work under circumstance in which the conditions of rest and work were combined. Four experimental conditions based on rest types and work content were designed as follows: 1, (input of interesting sentences) + (dynamic rest); 2, (input of interesting sentences) + (static rest); 3, (input of meaningless numbers) + (dynamic rest); and 4, (input of meaningless numbers) + (static rest).

One operation unit was comprised of 50 min of VDT work and 15 min of rest. Subjects were assigned to three operation units in both the morning and afternoon.

Flicker test, kinetic vision examination, inquiry into subjective symptoms, and test of single digit addition for 10 minutes according to Kraepelin's examination were conducted both before and after morning and afternoon operation sessions, for four times per day. Flicker test and kinetic vision examination were carried out immediately before and after each individual operation unit.

Results obtained are shown as follows:
1) When input conditions were compared, e.g. sentence input vs. number input, there was no significant difference in the complaint rate of subjective symptoms, the amount of single digit addition or in Flicker test value. The decrease in kinetic vision levels after each afternoon operation in the sentence input group was slightly smaller than that in the number input group.
2) When rest conditions were compared, there was no difference in the results of total input, Flicker test value and amount of single digit addition between dynamic rest and static rest. The complaint rate of subjective symptoms in the static rest group at the end of afternoon operations, increased remarkably as compared with the dynamic rest group.
3) The recovery of kinetic vision levels was more marked in the dynamic rest group than in the static rest group.

From these results, it is inferred that in order to recover from fatigue caused by VDT work, dynamic rest is more effective than static rest. Therefore, dynamic rest, applied at the job site should be an efficient means of recovery from fatigue.