Shrinkage and psychophysical load ratings in self-paced and force-paced lifting work and during recovery

The purpose of this study was to investigate the effects of the load on the human spine during force-paced and self-paced lifting and subsequent rest. Five women and five men worked under self-paced and force-paced (4 lifts/min) conditions on two days lifting a box for 30,min. The weight of the box was determined by the rating of acceptable load (RAL) method. During the work the lift rate was observed, and subjects made rating of perceived exertion (RPE) in 5,min intervals. The stature was measured with a staturemeter before and after the work period and during the following 30,min rest lying. In self-paced work women had a higher lift rate than men (p<0·05). In general, RPEs increased towards the end of the lifting period but RPEs did not differ between women and men or between self-paced and force-paced work. The mean shrinkage during the 30,min work was in self-paced work 5·1 ±2·0 mm for women and 5·8± l·2mm for men, and in force-paced work 5·8 ± 2·3,mm and 6·8 ± 2·2,mm, respectively. There were no sig...