Perceived fatigue during physical work: an experimental evaluation of a fatigue inventory

The aim of this study was to investigate the validity of the SOFI (Swedish Occupational Fatigue Inventory). Twenty male and 20 female subjects exercised on a cycle ergometer, on three different work loads relative to their maximal capacity. Furthermore, they held one arm straight in 90 degrees forward flexion, on three different times relative to their maximal endurance time. After each occasion, perceived fatigue was rated on the SOFI and on Borg's CR-10 scale. The trials were conducted during two days. As expected, for dynamic work the highest ratings were obtained on Physical exertion, while static work mostly influenced the ratings on Physical discomfort. High ratings were also found on Lack of energy, and on the CR-10 scale after both work tasks. Men and women did not differ significantly with respect to their ratings. The content validity of the physical dimensions of the SOFI has been demonstrated. Further studies, with other types of activities, will be carried out to validate the two remaining factors, Lack of motivation and Sleepiness.