ECR Spotlight – Pablo Rozier-Delgado Free

Pablo Rozier-Delgado

How did you become interested in biology?

In 2017, I started a BSc in sports science at Université Grenoble Alpes, France. This degree offers a broad overview of human motricity, exploring a great panel of disciplines such as history, sociology, psychology, anatomy, neuroscience and much more. The opportunity to explore all these fields within the common ground of human movement was very exciting. I love exploring various disciplines, but I am mostly drawn to people filled with passion. A key encounter that definitely shifted my interests towards biology, and science in general, was when I met Baptiste Morel, my professor at the time, in my first year of a Master's degree at Université Savoie Mont-Blanc. The first lecture he gave was about muscle function and capacity – a quite familiar topic I had already been studying for 3 years. However, this time he taught us about muscle function on a much larger scale; from what we were used to – such as runners during sprints and marathons – to suddenly explaining to us how fatigue applies to the muscles of fishes and crabs. This lesson was filled with enthusiasm, was so intriguing and was definitely my first step into comparative physiology.

Describe your scientific journey and your current research focus

So far, my scientific journey has gravitated around the evaluation of physical abilities, which is crucial for both health- and ecology-related purposes. Indeed, my first research experience, during my Master 1, was to investigate the force–velocity capacities of cyclists alongside Baptiste Morel and Maximilien Bowen – researchers who developed a conceptual framework for understanding muscle force production in relation to contraction velocity and time. During my Master 2 work, I developed a methodology to assess the physical capacities and fatigue of patients using accelerometers. Now I'm in my first year of PhD work, my supervisors, Baptiste Morel and Anne Loison, and I are working as an interdisciplinary team of ecologists and sports scientists to develop these approaches with free-ranging animals. While my scientific career has been methodology-oriented so far, I am keen to start addressing the questions that this work has raised. For example, evaluating physical capacity without any testing could help to regulate chemotherapy and its associated toxicities. Our model could also enable us to predict fatigue during predator–prey interactions or observe the effects of external factors, such as climate change and associated temperature rises, on animals' physical capacities and behaviour.

How would you explain the main findings of your paper to a member of the public?

The underpinning physiology of a moving animal is characterised by a threshold effect. Below a critical intensity, metabolic processes remain stable and effort can be sustained for hours; this is called the heavy domain of exercise. However, beyond this critical intensity, in the severe domain, homeostasis cannot be preserved and fatigue develops drastically, ultimately leading to exhaustion. Leveraging methods from the sports science field, we developed a methodology for evaluating the critical intensity from Global Navigation Satellite Systems with free-ranging domestic dogs. We show that the critical intensity measured in natura allows the characterisation of endurance capacities and is reliable across sessions. This new physical ability evaluation can also distinguish breeds. This offers the fantastic possibility of characterising the physical abilities of wild animals, where laboratory-controlled testing is difficult to perform. Moreover, once the ability has been assessed, it is possible to investigate the animal's behaviour; when an animal moves at fatiguing intensities and where in the landscape it occurs.

Why did you choose JEB to publish your paper?

While the current trend is to seek for the biggest metrics, I personally find to be far more fulfilling to publish in historic journals; to me, there is much more prestige from maintaining a journal at the top for decades than boosting its impact factors. Moreover, publishing in Journal of Experimental Biology allows me, at my scale, to continue the legacy of pioneers in our field. No one is purely original and no scientific advance emerges from nothingness. Throughout history, JEB has provided classic papers which have laid the foundations for my work and make me ‘stand on the shoulders of giants’ as written by the English philosopher John of Salisbury but erroneously attributed to the great Isaac Newton. I am grateful to publish my work in JEB, host for pioneering researchers' work in my field from Nobel Prize winners A. V. Hill in the 1930s and A. Krogh in the 1940s to C. R. Taylor in the 1980s and H. Pontzer in the 2000s.

What is your favourite animal, and why?

Despite our study being conducted on domestic dogs, I would answer the comb jelly Euplokamis, from the Ctenophora phyla. It has long tentacles, a complex nervous system and bioluminescent capabilities. However, its most striking feature surely is its striated muscle. In this article, we were interested, inter alia, in the relationship between effort intensity and duration at the locomotion scale. Yet, astonishingly, this relationship is conserved throughout scales even at the level of the muscular fibre (known thanks to the pioneering works from A. V. Hill). That is why, what we classically study in humans – who have striated muscles – could be transferred to other animals that share identical muscle structures and properties. Euplokamis is one of them. However, analogously to Cnidarians, its striated muscles could have evolved completely independently from Bilaterians. This convergent evolution in both function and structure is mind-blowing, and offers hypothetically the possibility to study its endurance.

Do you have a top tip for others just starting out at your career stage?

I am at a very early stage in my career, but I found one piece of advice to have been of great help. A researcher and a friend of mine, Maximilien Bowen, told me this: ‘To pursue a PhD thesis, you need three conditions: the best advisors, topic and environment for you’. I am happy to say that I have checked the full list; I have great supervisors both professionally and personally, I am certainly enjoying the topic I am working on, and people are great and it is a pleasure to go skiing in the French Alps.

Indeed, my advice would be not to rush the process: you are going to board a 3 year journey, so it is important to ensure that it will be enjoyable along the way. I took the time to build my thesis project with passionate people I enjoy being around. This has made my everyday work fulfilling and opened up a whole new world for me: animal ecology.

What's next for you?

I have still more than 2 years of PhD. My work will focus on assessing physical capacities and modelling fatigue of wild animals with accelerometers. Based on the works of T. Garland Jr and C. R. Taylor, I will investigate both anaerobic and aerobic capacities of free-ranging animals at an interspecific level. While previous efforts have focused on ‘Which species is the fastest?’, I aim to answer the question: ‘Who is the fastest, and for how long?’. I also look forward to new academic adventures after my PhD.