Reply to the letter: To consider the exercise density in the dose–response relationship: the idea is promising, the operationalization tricky!

We thank Desgorces for taking the time to read our recent publication in the European Journal of Applied Physiology (Herold et al. 2025b) and providing an insightful commentary (Desgorces 2025). In his commentary, Desgorces (2025) supports our view that density is an important variable for analyzing and prescribing the dose and dosage of physical activity (PA) in the consideration of their effects on brain health. However, he also acknowledges that quantifying PA density is challenging, which is underlined by different perspectives on its definition, operationalization, and interpretation. In this context, we are pleased to have the opportunity for further clarification and for a constructive discussion by providing our perspective on the points raised by Desgorces (2025) in this reply. While we acknowledge the points raised in Desgorces’ commentary (2025), our response provides additional support for our understanding of PA density as conveyed in our initial review.