## 4 Discussion
The inability to raise lactate values in the \(100+20\) W incremental cycling test in these national-level cyclists more likely reflect poor substrate utilization than poor physical form. Low glycogen stores and the inability to support optimal recovery and growth and substrate utilization during maximal load are reasons that have been proposed before. We did not find any association between WDEB\({}_{\text{neg}}\) and performance. This suggests that the severity of energy deficiency (as observed by WDEB\({}_{-300}\)) could potentially have an impact on anaerobic metabolism rather than just time spent in energy deficiency (as reflected by WDEB\({}_{\text{neg}}\)). This is further supported by our observation from diary logs that the majority of participants had poor or absent EI during long strenuous activities, which resulted in greater hours spent in WDEB\({}_{-300}\). Better nutritional practices are widely recommended to support optimal performance and recovery [28]. With this paper, we would like to confirm that among female cyclists, EI is especially problematic during training as they seem to be avoiding (excess) carbohydrate intake. The lactate values at the end of the test reflect anaerobic metabolism. The inability to raise these values can reflect poor physical form, overtraining, or suboptimal substrate utilization. As cyclists involved in this study were top national contenders, the last two options seem more likely. Lactate metabolism reflects the ability to perform in anaerobic metabolism. Two theoretical mechanisms could explain the result of our study. We did not measure glycogen levels directly, but it is known that spending more time in a catabolic state that fails to fill glycogen stores could result in a suboptimal glycogen reserve at the beginning of training [29]. This would support fat metabolism soon after starting physical activity. Fat metabolism is, unfortunately, not as effective when anaerobic metabolism takes place during high training loads [30]. This leads to lactate values that are not as high as in optimal circumstances. The other possibility is the failure to use the glycogen storage, as almost all cyclists failed to replenish carbohydrates during any training. This could also propagate fat metabolism even when glycogen stores are not empty due to failure in optimal substrate utilization. To our knowledge, this is the first study to investigate performance and WDEB in competitive female cyclists. This research demonstrates that performance in professional female cyclists might be more dependent on daily fluctuations in energy balance rather than on EA. In the future, more studies, including blood markers and actual racing results, might be sensible in supporting the finding of this paper. We would also like to suggest future research should use WDEB and direct EA measurement for the categorization of participants in research assessing LEA performance effects rather than questionnaires such as LEAF. This might provide useful insight into the mechanism of LEA impairing performance. A possible practical application of this study is that cyclists could benefit from measuring REE. A decline in their mREE could be an indicator of impaired endurance performance. More studies are needed to provide final conclusions. The authors would like to acknowledge some limitations of this study. Baseline individual differences are not completely accounted for. Behavioral patterns have not been studied in this paper, and temporal analyses [31] that could have an impact on performance have not been used [32]. All participants included in the performance analysis were from the same cycling team, competing at the same level. This is how we tried to eliminate any major differences in baseline performance characteristics. This study is not properly powered due to the suboptimal sample size. However, measurements of LEA are time consuming and exhausting for the athletes, and it is difficult to obtain proper participation.