The objective of this study was to investigate how muscular fatigue affects the human's perception of weights. The main goal was to test the hypothesis that human's perception of weight is different if the muscle is fatigued than if it is not. Forty subjects (20 males and 20 females) between the ages of 18 and 30 yr participated in this experiment. A set of weights was made from plastic containers filled with lead shots. The containers weighed between 50 and 500 g in increments of 50 g resulting in ten variable weights. Subjects were tested, before and after training, on the use of Borg's RPE scale. The results showed that subjects were able to learn to use the RPE scale after only two training sessions. Next, subjects were asked to exert and maintain a maximum push-down force with the right arm until fatigued. Immediately after fatigue, subjects had to lift two weights in both the left and right arms simultaneously and compare the weight in the right arm (variable weight) to the one in the left arm (constant weight) and rate it on the RPE scale. The same process was followed without fatiguing the right arm. The results showed that when muscles were not fatigued, the RPE values coincided well with the tested weight, such as 500 g represented number 10, and 50 g represented number 1 on the RPE scale. However, when muscles were fatigued, the RPE values were significantly lower. The results showed that subjects perceived the weight to be about 17% less.
