Research database

Physical inactivity is a main curse of modern society, ranked in 2nd place by the WHO 2019 report as risk factor of overall mortality (from the 7th place of 2006), causing 5 million deaths per year. Inactivity and muscular disuse are a frequent phenomenon occurring variably with sedentary lifestyle or even with limb or whole-body immobilization due to illness and hospitalization. It is characterized by a decline of the neuromuscular system, leading to a progressive loss of muscle mass, strength, and power, and to an accelerated worsening of oxidative metabolism1. These conditions could ultimately result in reduced mobility and loss of independence. Recent home confinement measures taken during COVID-19 era have increased even more the interest about the detrimental impact of inactivity and muscle disuse and what possible exercise countermeasures should be employed1. Further, denervation-reinnervation processes, resulting in fewer but larger surviving motor units in advanced age, start as early as age 50–60yr and can be magnified in older adults (>75yr), and muscle strength/power reduction is accelerated after 50yr; thus, the curse of inactivity may have even greater impact in older age. Exercise countermeasures and restoration of physical activity seem to be highly beneficial for neuromuscular impairments recovery2. However, there is a preoccupying paucity of data regarding the best reconditioning strategies with population experiencing forced reduction of physical activity or even complete disuse. There is a need to better elucidate how the neuromuscular system recovers after a period of disuse (or reduced usage) in response to different exercise paradigms. Moreover, it is urgent to clarify whether neuromuscular functional recovery after inactivity differently responds to resistance and endurance stimuli and if age will influence such responses. In this project we will characterize the neuromuscular, structural, and metabolic adaptations to endurance vs. resistance exercise modalities applied as countermeasures to both an inactivity model (step reduction) and complete disuse (bed rest) in young and older age.