Physical inactivity is a pandemic with severe implications for global public health, representing a major cause of chronic diseases and mortality. Understanding the pathophysiological mechanisms driving the adverse effects of physical inactivity is crucial for developing effective countermeasures. This session aims to raise awareness and share new insights regarding the detrimental impact of muscle disuse on various physiological systems. Dr. Lucrezia Zuccarelli and Dr. Fabio Sarto will present cutting-edge research on the impact of physical inactivity on the cardiorespiratory and neuromuscular systems, respectively. Their presentations will focus on physiological studies combining in vivo and ex vivo measurements to provide a comprehensive understanding of the subject. Prof. Uros Marusic will conclude the discussion with a focus on the effects of inactivity on the central nervous system, delving into sensorimotor alterations in both young and older adults subjected to bed rest. These implications will be illuminated through an array of investigations ranging from static high-density electroencephalographic measurements to dynamic Mobile Brain/Body Imaging technology. The speakers will present findings from different populations and experimental models of physical inactivity. The session will be of interest to researchers in human physiology and neuroscience. Furthermore, it offers relevant insights to sports medicine doctors, muscle biologists and health practitioners.
ECSS Paris 2023: IS-PN07
Oxidative metabolism represents the main energy source for activities in everyday life. Functional evaluation of oxidative metabolism during exercise provides important information on the physiological responses required by the cardiovascular and respiratory systems to meet the skeletal muscle metabolic demand. Whereas cardiovascular impairments associated with (or responsible for) the decreased peak oxygen uptake (V̇O2peak) during inactivity have been described, more peripheral impairments have been relatively less investigated. Over the last 15 years, new exciting evidence has been published regarding the impairment of skeletal muscle oxidative metabolism during conditions of drastic physical activity reduction (i.e., bed rest interventions). In this presentation, Dr. Lucrezia Zuccarelli will focus on the localisation of the main site(s) of impairment in oxidative metabolism during exercise following inactivity along the O2 pathway from the ambient air to skeletal muscle mitochondria, with a particular interest in the peripheral level. Biomarkers of impairment related to peripheral vascular and endothelial function, the intramuscular matching between O2 delivery and O2 uptake and mitochondrial function during exercise in young and elderly will be presented. A refinement of available tools and methods aimed at enhancing oxidative metabolism and improving aerobic performance would allow to increase the general quality of life of both healthy people and patients. This concept, besides being of interest from a basic science point of view, may be of interest also for other pathological conditions characterized by relatively short periods of profound inactivity, and it could affect the definition of countermeasures rather than rehabilitative interventions.
Read CV Lucrezia ZuccarelliECSS Paris 2023: IS-PN07
Periods of disuse lead to rapid and marked decreases in muscle mass and force. Interestingly, the reported loss of muscle function largely exceeds that of muscle size, suggesting an impairment in the intrinsic capacity of muscle force production. Although a clear and exhaustive explanation of this phenomenon is still lacking, there is growing evidence that neuromuscular impairment may be a key player in this scenario. In this presentation, Dr. Fabio Sarto will present published and unpublished data that provide new insights into the muscle morphological, functional, electrophysiological and molecular alterations across different experimental models of physical inactivity. Evidence that will be presented unequivocally shows that even brief periods of disuse induce initial signs of myofibre denervation, impairment of excitation-contraction coupling, neuromuscular junction instability, axonal damage and downregulation of skeletal muscle ion channels genes. Furthermore, it will be discussed how alterations in motor unit properties, such as elevated number of turns (reflecting increased motor unit potential complexity) and decreased motoneuron firing rate, have been identified in different studies leveraging gold-standard electromyographic techniques. The differential adaptations of young and older adults in response to muscle disuse will be discussed. Finally, the reversibility of these neuromuscular changes with subsequent retraining periods based on resistance exercises will also be explored.
Read CV Fabio SartoECSS Paris 2023: IS-PN07
Brain plasticity, also known as neuroplasticity, highlights the brains remarkable ability to adapt and reconfigure itself in response to different experiences, with physical activity being a well-researched factor in this process. However, neuroscience has paid comparatively little attention to the consequences of prolonged inactivity on the central nervous system. Research on bed rest studies has shed light on the functional decline observed in both young and older adults following extended periods of physical inactivity, yet the underlying neural mechanisms remain elusive. In this presentation, Dr. Uros Marusic will present the latest findings from studies with 10 and 21 days of bed rest in young and older adults. In these studies, high-density electroencephalography was used to investigate sensorimotor processes. The assessment includes both static measures, such as visual-evoked potentials and motor-related cortical potentials, and dynamic assessments of functional performance before and after bed rest using Mobile Brain/Body Imaging technology, which provides a comprehensive insight into the neural changes associated with prolonged physical inactivity.
Read CV Uros MarusicECSS Paris 2023: IS-PN07