We write regarding the editorial by Rodríguez et al.1 published in Revista Española de Cardiología.

First, we would like to congratulate the authors for the initiative and for the work carried out. However, to derive the greatest benefit from the suggestions, we believe it opportune to offer some comments on the published article that could result in clearer, more specific guidance.

In the article, when the authors refer to increased susceptibility to infection due to physical exercise, they point out the limitation and the need for more studies regarding the type of exercise, mentioning quantity and intensity in parentheses. Type of exercise is already in itself a variable, the same as volume and intensity. In fact, the variable “type of exercise” determines the level of intensity and also affects the volume.2,3 We believe that a better definition of the meaning of the text is possible. To be clear, we completely agree regarding this meaning, but a large part of such lack of specification in research comes from the insufficient definition and manipulation of these variables.4

At the end of the same paragraph, the authors refer to variables again, this time the “quantity” and “duration” as 2 distinct variables, when in reality they are part of the same variable, volume.

The next part that caught out attention, and which is probably one of the most important points of this letter, was the table containing the recommendations of the different scientific societies. We wanted to check the type and details of these recommendations and we found, based on the references in the article, the inclusion of individual recommendations, attributed as coming from a whole scientific society, for example the Spanish Society of Cardiology/Spanish Heart Foundation (SEC/FEC), when in fact the text was produced by an individual professional in the FEC blog. As you will be aware, normally, when one uses the name of a scientific society and attributes recommendations to that institution, this is done after consensus from various members, and they usually appear in more high-profile articles than a blog written by an individual. We do not mean that the advice of our colleague is incorrect, but that it should not be attributed to the SEC/FEC as a whole.

We also believe that a more critical review was required regarding incomplete and sometimes inappropriate components of these recommendations. We realized that not only were there no reference values for minimum or maximum intensities, but that exercise with “own body weight” was recommended in many cases, something which, for a large part of the population (especially that indicated in the document) represents a very high relative intensity.

The use by some institutions of “online routines” (not a very precise term) or “active computer games” are highly generic recommendations that are not accompanied by indications to determine their usefulness, safety, or efficacy. This factor could also lead to underestimating the value of an appropriately led and supervised training program.

We hope that these comments will be considered from a constructive perspective and with the greatest of respect regarding the authors’ work: we again would like to make it clear that we consider their proposal to be highly interesting and valuable.