INTRODUCTION: The NASA-TLX questionnaire [1] assesses six independent dimensions (mental, physical and temporal demand, own performance, effort, frustration) composing mental workload. Its sensitivity was tested according to the magnitude of effort, gender, age expertise and progress. METHODS: Fifty subjects divided according to gender (27 men, 23 women), expertise (33 experts, 17 recreational), and age (34 adults, 16 youths) performed a maximal 400-m front crawl. Experts also performed 100-, 200- and 300-m trials at the velocity of the previous 400-m, and retested on the maximal 400-m after three months of aerobic training. ANOVAs examined age, gender, expertise, distance and training effects on total workload (TWL) and other dimensions of the NASA-TLX. RESULTS: Women had lower TWL (48±9 vs. 54±2, p<.05) and effort (59±13 vs. 70±21, p<.05) level than men. No difference based on expertise was observed for any dimension of the TLX. Youth had lower TWL (47±6 vs. 53±10, p<.05) and temporal demand (36±20 vs. 57±20, p<.05) than adults. From 100- to 400-m, a significant increase was recorded in TWL (32±28 vs. 50±28, p<.05), physical demand (21±22 vs. 65±29, p<.05) and effort (32±16 vs. 63±19, p<.05). After three months of training, no significant difference in TWL was noted, although swimmers with improved performance exhibited lower scores in frustration (50±25vs30±15, p<.05) and own performance (64±22 vs. 35±19, p<.05) and higher scores in effort (46±25 vs. 64±16, p<.05). DISCUSSION: The TLX-NASA questionnaire is sensitive to the objective task demand rather than to the participant`s level, although some variations were seen in gender and age groups. The retest condition indicated its overall reliability, and analysis of its dimensions allows subtle changes to be highlighted. It thus seems to be an interesting tool for coaches and scientists alike.
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