1. Alterations in Muscle Contractile Properties, Structure, and Function During 10-Day Bed Rest, Post-Recovery, and Following COVID-19 LockdownBoštjan Šimunič, Martino V. Franchi, Fabio Sarto, Elena Monti, complete scientific database of research data Abstract: We aimed to identify early tensiomyography alterations in six muscles during a 10-day bed rest (BR10), followed by a 30-day recovery period (R+30), and to compare these changes with those observed after the 54-day COVID-19 lockdown in ten healthy males (22.9 ± 5.0 years). Tensiomyography and muscle thickness (sonography) were assessed at baseline, during bed rest, at BR10, R+30, and after the COVID-19 lockdown. Additional assessments included vertical jump performance (force plate), body composition (bioimpedance), physical activity (GPAQ), and lower back pain (VAS). By BR10, participants experienced a 1.9% body mass loss, a 3.8% increase in fat mass, and a 2.4% reduction in muscle mass. While anthropometric parameters returned to baseline by R+30, fat mass increased again by 3.9% post-lockdown. Jump height declined by 10.1% at BR10, returned to baseline at R+30, and remained stable thereafter. Muscle thickness decreased by 7.0% in the vastus lateralis at BR10 and by 10.1% post-lockdown. Tensiomyographic amplitude increased in all five leg muscles prior to BR10, recovered at R+30 and increased again after the COVID-19 lockdown, while a reduction was observed in the erector spinae within the first 48 hours, coinciding with reported lower back pain. In the erector spinae, both delay and contraction time decreased during BR10 and post-lockdown. In contrast, contraction time of the biceps femoris increased before BR10 and remained elevated post-lockdown. Overall, tensiomyographic parameters after the COVID-19 lockdown changed in the same direction as during bed rest, though to a lesser degree, make it a sensitive tool for detecting changes in muscle structural and functional quality after bed rest and reduced activity paradigms.
Keywords: Atrophy, Bed rest, Physical inactivity, Skeletal muscle, Tensiomyography
Published in DiRROS: 25.06.2025; Views: 384; Downloads: 0
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2. Twenty-one days of bed rest alter motor unit properties and neuromuscular junction transmission in young adultsFabio Sarto, Miloš Kalc, Evgeniia Motanova, Martino V. Franchi, Daniel W Stashuk, Nina Murks, Giacomo Valli, Samuele Negro, Tomaž Prašnikar, Mladen Gasparini, Giovanni Martino, Giuseppe De Vito, Aleš Holobar, Boštjan Šimunič, Rado Pišot, Marco Vincenzo Narici, 2025, original scientific article Abstract: Previous studies showed that properties of higher‐threshold motor units (MUs) and neuromuscular junction (NMJ) function are preserved during short‐term disuse. This study aimed to test how a longer disuse period affects MU properties, NMJ transmission, and NMJ morphology remodeling. Nine young healthy males (age: 18‐29 years) underwent 21 days of horizontal bed rest. Pre‐ (BR0) and post‐bed rest (BR21), quadriceps maximal voluntary contraction (MVC), and size were assessed. We combined intramuscular electromyography (iEMG) and high‐density surface electromyography (HDsEMG) recordings on the vastus lateralis to assess MU properties at 25% and 50% of MVC. Muscle biopsies and blood samples were also collected. Quadriceps MVC and size decreased at BR21. We found alterations in MU properties at both contraction intensities, including reduced discharge rate, MU potential area changes, and increased complexity. NMJ transmission was found to be reduced at BR21 at 25% MVC. This functional NMJ impairment was biochemically corroborated by an increase in serum C‐terminal agrin fragment concentration, a biomarker of NMJ instability. In addition, a direct assessment of NMJ morphology revealed the presence of some denervated NMJs exclusively at BR21. In conclusion, 21‐day bed rest altered MU properties across different contraction intensities and impaired NMJ transmission with initial signs of remodeling/denervation. Disuse duration appears to be a critical factor, as previous shorter studies failed to detect some of these changes. We believe these findings are clinically relevant for disuse after trauma, surgery, or illness, and may support the development of effective countermeasures.
Keywords: disuse, unloading, physical inactivity, electrophysiology, electromyography
Published in DiRROS: 13.05.2025; Views: 564; Downloads: 252
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3. Effects of a 2-year exercise training on neuromuscular system health in older individuals with low muscle functionElena Monti, Sara Tagliaferri, Sandra Zampieri, Fabio Sarto, Giuseppe Sirago, Martino V. Franchi, Andrea Ticinesi, Yari Longobucco, Elisa Adorni, Marco Vincenzo Narici, 2023, original scientific article Keywords: skeletal muscles, C-terminal agrin fragment, neurofilament light chain, exercise interventions, sarcopenia, elderly
Published in DiRROS: 15.12.2023; Views: 1333; Downloads: 680
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4. Upregulation of sarcolemmal hemichannels and inflammatory transcripts with neuromuscular junction instability during lower limb unloading in humansGiuseppe Sirago, Julián Candia, Martino V. Franchi, Fabio Sarto, Elena Monti, Luana Toniolo, Carlo Reggiani, Emiliana Giacomello, Sandra Zampieri, Marco Vincenzo Narici, 2023, original scientific article Keywords: skeletal muscles, neuromuscular junction, sarcolemmal hemichannels, lower limb
Published in DiRROS: 14.12.2023; Views: 1219; Downloads: 659
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5. Pathophysiological mechanisms of reduced physical activity : insights from the human step reduction model and animal analoguesFabio Sarto, Roberto Bottinelli, Martino V. Franchi, Simone Porcelli, Boštjan Šimunič, Rado Pišot, Marco Vincenzo Narici, 2023, review article Abstract: Physical inactivity represents a heavy burden for modern societies and is spreading worldwide, it is a recognised pandemic and is the fourth cause of global mortality. Not surprisingly, there is an increasing interest in longitudinal studies on the impact of reduced physical activity on different physiological systems. This narrative review focuses on the pathophysiological mechanisms of step reduction (SR), an experimental paradigm that involves a sudden decrease in participants’ habitual daily steps to a lower level, mimicking the effects of a sedentary lifestyle. Analogous animal models of reduced physical activity, namely the “wheel-lock” and the “cage reduction” models, which can provide the foundation for human studies, are also discussed. The empirical evidence obtained thus far shows that even brief periods of reduced physical activity can lead to substantial alterations in skeletal muscle health and metabolic function. In particular, decrements in lean/muscle mass, muscle function, muscle protein synthesis, cardiorespiratory fitness, endothelial function and insulin sensitivity, together with an increased fat mass and inflammation, have been observed. Exercise interventions seem particularly effective for counteracting these pathophysiological alterations induced by periods of reduced physical activity. A direct comparison of SR with other human models of unloading, such as bed rest and lower limb suspension/immobilisation, is presented. In addition, we propose a conceptual framework aiming to unravel the mechanisms of muscle atrophy and insulin resistance in the specific context of reduced ambulatory activity. Finally, methodological considerations, knowledge gaps and future directions for both animal and human models are also discussed in the review.
Keywords: physical inactivity, cage reduction, insulin sensitivity, muscle atrophy
Published in DiRROS: 29.06.2023; Views: 1376; Downloads: 883
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6. Neuromuscular junction instability and altered intracellular calcium handling as early determinants of force loss during unloading in humansElena Monti, Carlo Reggiani, Martino V. Franchi, Luana Toniolo, Marco Sandri, Andrea Armani, Sandra Zampieri, Boštjan Šimunič, Rado Pišot, Marco Vincenzo Narici, 2021, original scientific article Abstract: Unloading induces rapid skeletal muscle atrophy and functional decline. Importantly, force is lost at a much higher rate than muscle mass. We aimed to investigate the early determinants of the disproportionate loss of force compared to that of muscle mass in response to unloading. Ten young participants underwent 10 days of bed rest (BR). At baseline (BR0) and at 10 days (BR10), quadriceps femoris (QF) volume (VOL) and isometric maximum voluntary contraction (MVC) were assessed. At BR0 and BR10 blood samples and biopsies of vastus lateralis (VL) muscle were collected. Neuromuscular junction (NMJ) stability and myofibre innervation status were assessed, together with single fibre mechanical properties and sarcoplasmic reticulum (SR) calcium handling. From BR0 to BR10, QFVOL and MVC decreased by 5.2% (P = 0.003) and 14.3% (P < 0.001), respectively. Initial and partial denervation was detected from increased neural cell adhesion molecule (NCAM)-positive myofibres at BR10 compared with BR0 (+3.4%, P = 0.016). NMJ instability was further inferred from increased C-terminal agrin fragment concentration in serum (+19.2% at BR10, P = 0.031). Fast fibre cross-sectional area (CSA) showed a trend to decrease by 15% (P = 0.055) at BR10, while single fibre maximal tension (force/CSA) was unchanged. However, at BR10 SR Ca2+ release in response to caffeine decreased by 35.1% (P < 0.002) and 30.2% (P < 0.001) in fast and slow fibres, respectively, pointing to an impaired excitation%contraction coupling. These findings support the view that the early onset of NMJ instability and impairment in SR function are eligible mechanisms contributing to the greater decline in muscle force than in muscle size during unloading.
Keywords: Ca2+ dynamics, muscle atrophy, neuromuscular junction instability, sarcoplasmic reticulum, single fibre atrophy, single fibre contractile impairment, unloading
Published in DiRROS: 16.06.2021; Views: 2267; Downloads: 2017
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7. Impact of sedentarism due to the COVID-19 home confinement on neuromuscular, cardiovascular and metabolic health : physiological and pathophysiological implications and recommendations for physical and nutritional countermeasuresMarco Vincenzo Narici, Giuseppe De Vito, Martino V. Franchi, Antonio Paoli, Tatiana Moro, Giuseppe Marcolin, Bruno Grassi, Giovanni Baldassarre, Lucrezia Zuccarelli, Gianni Biolo, Filippo Giorgio Di Girolamo, Nicola Fiotti, F. Dela, Paul L. Greenhaff, Constantinos Maganaris, 2020, original scientific article Keywords: COVID-19, sedentarism, neuromuscular system, cardiovascular system, glucose homeostasis, body composition, nutrition, exercise
Published in DiRROS: 18.12.2020; Views: 2372; Downloads: 671
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