The role of perception of effort in endurance performance testing and training

The role of endurance performance measurements have been an important theme, cycling time trials are main elements of Grand Tour cycling events, such as the Tour de France. Normally time trials within road cycling championships cover distances between 10 and 44 km over periods of 10 min to 60 min. afterward, success in these individual tests of human endurance is widely determined by the cyclist's level of aerobic fitness. Furthermore, focussing on all endurance performance methods to assess athlete's level, there is not only physiological assessment for endurance performance. Perceived exertion, defined as "the conscious sensation of hard, heavy and strenuous exercise", is identified to regulate human behaviour and endurance exercise performance, moreover, rating perceived exertion has been valid tool to demonstrated endurance performance as well as physiological parameters (heart rate and blood lactate concentration, and exercise economy) during submaximal exercise performance. As there are a numerous studies suggested that perception of effort can determine endurance exercise performance independently of alterations in cardiorespiratory, metabolic and neuromuscular parameters. Therefore, it is possible that perception of effort plays a major role in determining endurance performance. Therefore, from these perceptive the idea for first study has been developed

However, to date, not only to clarify RPE's correlation to endurance performance but also how manipulations of perceived exertion might influence endurance performance remain not well understood. The secondary aim of this thesis was to examine how manipulations of perception of effort might affect endurance performance. This manipulation is divided in two parts: The effect of mental fatigue on critical power and the anaerobic work capacity and Does chronic use of caffeine reduce its acute ergogenic effects during high intensity interval training? We firstly investigated the effect of impairing perception of effort via mental fatigue involving the response inhibition process on critical power endurance performance. These studies have demonstrated higher perceptions of effort and reduced exercise performance independently of alterations in cardiorespiratory or metabolic responses to exercise. Therefore, higher PE may limit TTE and subsequently alter the CP and W' independently of changes within the underlying muscle physiology. We found that contrary to endurance exercise performance, so the outcomes of this study were, mental fatigue induced by a response inhibition stroop task reduced time to exhaustion at fixed power outputs, the reduced time to exhaustion does not alter the resultant critical power. However, the development of mental fatigue did significantly reduce the supposed anaerobic work capacity, mental fatigue induced by a response inhibition stroop task significantly increased RPE during the TTE trials. Therefore, these findings provides strong evidence that the proposed physiological critical power model can be affected by purely psychological factors i.e. mental fatigue.

On the other hand, in second part the thesis investigated on the effect of caffeine on endurance performance based on extensive research showing positive effects on performance many athletes use caffeine before and during competitions, however, the use of caffeine during training is not well understood. As the study outcomes shows, no significant changes in VO2max were observed in either groups after 4 weeks of training. As hypothesised, caffeine acutely increased power output, HR and blood lactate during HIIT at both the baseline and follow-up assessments. There were no significant interactions and main effects of time suggesting the development of tolerance to these acute ergogenic effects of caffeine during HIIT after 4 weeks of chronic supplementation. Caffeine ingestion one hour prior to HIIT acutely increases power output, HR and blood lactate for the same RPE. Frequent use of caffeine before training (3 times a week for 4 weeks) does not reduce these acute ergogenic effects of caffeine during HIIT. This observation argues against the development of tolerance and suggests that pre-training caffeine ingestion is a useful strategy to increase training intensity, whether this increase in training intensity leads to greater gains in performance needs to be investigated in future studies with more controlled training programs and longer follow up periods.

Overall, when merging all experimental parts, provides new vision on how perception of effort a valid and effective regulates of endurance performance. Specially, it proves how muscle fatigue is one of the contributor of the constant increase in perception of effort during endurance exercise, however, there are other contributors play a role in this increase and decrease in perceived exertion. In contrast, we demonstrated for the first time that i) perception of effort can be endurance performance regulator, ii) alterations in the attendance of mental fatigue does decrease endurance performance and increase perception of effort, iii) endurance performance can be improved by caffeine ingestion one hour prior to HIIT acutely increases power output, HR and blood lactate for the same intensity. Frequent use of caffeine before training does not reduce these acute ergogenic effects of caffeine during HIIT.