Effect of work-rest schedules on spinal shrinkage in the sedentary worker

The relationship between duration and frequency of rest intervals and spinal shrinkage was investigated. The objective was to determine whether the amount of spinal shrinkage can be significantly reduced by rest breaks during which the individual is either walking or standing rather than sitting. Seven subjects were studied during 4-h sessions for four consecutive days. During each session the subject sat and typed for a total of 3 h 20 min. Forty minutes of rest breaks were dispersed throughout the 4-h period. One condition was administered during each day with either eight breaks of 5 min, four breaks of 10 min, two breaks of 20 min or a single break of 40 min at the end of the work session. Using a stadiometer, changes in stature were measured with an accuracy of about 0.2 mm. Measurements were taken at the beginning of each work period and before and after each rest break. For the conditions with rest breaks of 20 or 40 min, there was significantly less shrinkage at the end of the 4-h work session.