The Association Between National Aeronautics and Space Administration Task Load Index Subscales, Training-Induced Fatigue, and Physiological Responses in Endurance Athletes.

PURPOSE: Traditional training metrics do not distinguish between the different components of internal training load contributing to training-induced fatigue, whereas the National Aeronautics and Space Administration Task Load Index (NASA-TLX) may offer a compelling multidimensional alternative. However, the NASA-TLX subscales have been overlooked in the context of endurance training. Therefore, this study investigated whether the NASA-TLX subscales are associated with acute performance decrement (APD) and physiological responses across different endurance training sessions.

METHODS

Twelve well-trained runners (10 males, 2 females; age 26.8 [6.9] y; maximal oxygen uptake [VO2max] 65.6 [6.4] mL·kg-1·min-1) completed 6 visits in the laboratory, an incremental test, a time to exhaustion (TTE) test, and 4 experimental training sessions in randomized order. A TTE test was performed at baseline and after each of 4 exercise sessions: low-intensity training, medium-intensity training, long-interval high-intensity (HITlong), and short-interval high-intensity (HITshort). APD was calculated as the percentage drop in TTE compared to baseline. The NASA-TLX questionnaire was administered between each training session and the TTE test to assess mental demand, physical demand, temporal demand, effort, frustration, and perceived performance.

RESULTS

All sessions led to significant APD (P = .041), with HITlong producing greater APD than low-intensity training (P = .035). Subscale analysis showed lower mental, physical, temporal, and effort scores after low-intensity training compared to HIT sessions (P < .001). All subscales were significantly correlated with APD and key physiological ventilatory and metabolic parameters (P < .001).

CONCLUSION

NASA-TLX subscales appear valid and may help athletes to discriminate distinct components of perceived workload.