The authors present a pilot study exploring the impact of aerobic and anaerobic exercises on glucose, lactate and ketones after consuming a carbohydrate-rich breakfast and omitting insulin in a sample of patients with T1D. Although some aspects of the manuscript could be interesting, it needs extensive revision and further reconsideration.
In particular, the authors should highlight the innovative aspects of their manuscript because they are not clear. What information are you adding to the current literature on exercise prescription in people with T1DM?
I also have several questions/concerns that need to be addressed by the authors. (Please, also check the word document).

Questions and comments:
1. Why did you enrol 21 patients and not a lower or higher number? Why only men?
2. The protocol should be more detailed, and several aspects are unclear (see the word file).
3. Why did you not compare the two modalities using a statistical approach?
4. How did you characterise the presence of long-term complications? Medical records?
5. Reading the abstract, the study design is not clear. In particular, I suggest to specify that exercises were separated by 1 to 6 weeks.
6. Why did you wait up to 6 weeks to perform the AE? Why did you not use the same time for all the participants? In one month or less, VO2 can change, particularly with a reduction of physical activity and increase of sedentary time. We have also to consider the impact of Covid and the government restrictions on the physical activity level. Did you assess the physical activity or VO2 during these weeks?
7. Considering the impact of exercise on insulin sensitivity, why did you monitor glycaemia only for 6 hours after training? Do you have the 24h data? If yes, I suggest to include this information in the manuscript because it could increase the quality of the article.
8. Why did you perform the exercise on the bike and not on the treadmill? Treadmill is more functional than a bike and may induce a higher metabolic response.
9. The authors stated that blood sample during exercise was taken each 3 minutes on the CPET and every 5 minutes on the AE. Why?
10. Were there statistical differences in the physical activity level among the participants? Do you think that physical activity level (e.g. low vs high) may impact glucose, lactate, and ketone patterns during and after exercise? I would say yes. In my opinion, you should exclude the two participants with a low PA level.

The article is ready.