Professor Niels Ørtenblad

Skeletal muscles have an impressive force and power generating capacity. However, with intense or prolonged activation they start to tire out, i.e. muscle function is reduced —a phenomenon known as muscle fatigue. This will be highlighted during summer 2024, where athletes from around the world were to gather in Paris for the Olympic festival of sport, which may be viewed as the paradigm of human muscle performance and failure.

Scientists have long been fascinated by this process, but many key questions remain unanswered about how activation per se is affected by exercise or disuse and how metabolism affects muscle regulation. One particularly intriguing aspect is how skeletal muscle fibres manage their energy. These fibres have a high and constantly changing energy demand, yet they skilfully balance energy use and production to avoid running out of fuel and maintain cell viability. Thus, muscle fatigue may not only be viewed as a failure of muscle function, but possibly should be considered as a protective mechanism avoiding muscle cell damage and ensure viability.

It has for more than a decade been known that carbohydrates are important for exercise performance and key substrate during both short intense and prolonged exercise. Later this has been explained by muscle glycogen, a stored form of glucose, which plays a crucial role in powering our muscles during exercise. By combining data from various sources—ranging from studies on elite athletes to detailed laboratory experiments, I have explored the metabolic factors that contribute to reduced muscle performance. A central focus of this research is muscle glycogen, a stored form of glucose. Recent findings by our team and others in the field suggest that glycogen isn't just a fuel reserve, it also acts as an energy sensor, playing a crucial role in muscle function and fatigue. This integrative approach helps us better understand how metabolism impacts muscle performance, paving the way for new insights into managing muscle fatigue.

During my talk I will discuss metabolic factors contributing to impaired force generating capacity, using an integrative approach, i.e. combining data from whole body human experiments, including high level athletes, though to more mechanistic models, I will particularly focus on the role of muscle glucose stores (glycogen), as we and colleagues in the field, have recently demonstrated that the muscle glycogen, serves as an energy sensor, contributing to muscle function and fatigue.

I am looking forward contributing to the “Festival of Failure” at Loughborough University’s Institute for Advanced Studies this Spring and share some of my research in the field of sports science and muscle physiology. My talk will focus broadly on muscle fatigue with special emphasis on role and mechanisms of carbohydrate and muscle glycogen in performance and fatigue. I await to discuss failure across more broad fields and disciplines and strengthen my established international research collaboration with Loughborough University.