1. Preserved mitochondrial respiration in presence of oxidative stress and reduced mitochondrial mass after 10-day bed rest in older adultsEvgeniia Motanova, Lucrezia Zuccarelli, Evgenii Lysenko, Stefano Amoretti, Marco Pirazzini, Ornella Rossetto, Lorenza Brocca, Roberto Bottinelli, Maria Antonietta Pellegrino, Giovanni Baldassarre, Clarissa Gissi, Giovanna Lippe, Mladen Gasparini, Boštjan Šimunič, Rado Pišot, Bruno Grassi, Marco Vincenzo Narici, 2026, izvirni znanstveni članek Povzetek: Ageing affects mitochondrial integrity in skeletal muscle, and physical inactivity may further exacerbate these changes. Although mitochondrial alterations are documented in ageing and disuse independently, how disuse impacts the mitochondrial phenotype in older populations remains unclear. This work aimed to characterise how physical inactivity impacts mitochondrial function, morphology and gene expression in the skeletal muscle of older adults. Ten healthy older men (65+ years) underwent 10 days of bed rest. Skeletal muscle biopsies were collected before and after bed rest to assess mitochondrial respiration (high-resolution respirometry), H2O2 emission, mitochondrial protein expression, morphology and volume density (electron microscopy) and transcriptomic profile. Ten days of inactivity increased mitochondrial reactive oxygen species (ROS) emission under non-phosphorylating conditions but did not impair oxidative phosphorylation (OXPHOS) capacity, indicating preserved respiratory efficiency. Consistently, mitochondrial respiratory complex and supercomplex protein abundance were unchanged. Mitochondrial mass decreased, as shown by reduced mitochondrial volume density. Reduced dynamin-like protein 1 (DRP1) phosphorylation at serine 637 was observed, whereas other mitochondrial fission and fusion protein levels remained unchanged. Mitochondrial morphology remained unaltered. Transcriptomic analysis revealed >3000 differentially expressed genes, characterised by downregulation of oxidative phosphorylation genes alongside altered mitophagy, antioxidant and oxidoreductase pathways. In summary, 10-day bed rest increased mitochondrial ROS emission and reduced mitochondrial mass in older skeletal muscle despite preserved respiratory function, indicating that elevated ROS production occurs upstream of respiratory dysfunction and is potentially linked to impaired antioxidant defence and ROS clearance. These findings suggest that preserving redox balance during inactivity may be a key strategy to maintain muscle health and functional independence in ageing populations.
Ključne besede: skeletal muscle, mitochondria, older adults, physical inactivity, mitochondrial respiration
Objavljeno v DiRROS: 11.09.2026; Ogledov: 56; Prenosov: 40
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2. Alterations in muscle contractile properties, structure, and function during 10-d bed rest, postrecovery, and after COVID-19 lockdownBoštjan Šimunič, Fabio Sarto, Martino V. Franchi, Elena Monti, Rado Pišot, Marco Vincenzo Narici, 2026, izvirni znanstveni članek Povzetek: We aimed to identify early tensiomyography alterations in six muscles during a 10-d bed rest (BR10), followed by a 30-d recovery period (R+30), and to compare these changes with those observed after the 50-d COVID-19 lockdown in 10 healthy males (22.9 ± 5.0 yr). Methods: Tensiomyography and muscle thickness (assessed by ultrasound imaging) 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 (Global Physical Activity Questionnaire), and lower back pain (VAS). Results: 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. Although anthropometric parameters returned to baseline by R+30, fat mass increased again by 3.9% postlockdown. 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% postlockdown. Tensiomyographic amplitude increased in five leg muscles before BR10, recovered at R+30 and increased again after postlockdown, whereas a reduction was observed in the erector spinae within the first 48 h, coinciding with reported lower back pain. In the erector spinae, both delay and contraction time decreased during BR10 and postlockdown, whereas contraction time of the biceps femoris increased before BR10 and remained elevated postlockdown. Conclusions: The observed post COVID-19 lockdown alterations in tensiomyographic parameters followed the same trend as those induced by bed rest, albeit with smaller magnitude. These findings support the utility of TMG as a sensitive and noninvasive method for monitoring muscle responses across different disuse paradigms.
Ključne besede: atrophy, disuse, skeletal muscle, tensiomyography, ultrasound
Objavljeno v DiRROS: 21.08.2026; Ogledov: 199; Prenosov: 192
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3. Mediterranean diet adherence, body composition, and recovery outcomes in hospitalised COVID-19 patients : a mixed-methods studyKaja Teraž, Boštjan Šimunič, Rado Pišot, Saša Pišot, 2026, izvirni znanstveni članek Povzetek: Introduction: The COVID-19 pandemic highlighted the importance of nutritional and lifestyle factors in recovery from severe illness, yet their role in post-hospitalization rehabilitation remains insufficiently understood. Methods: This study investigated the association between adherence to the Mediterranean diet, body composition, and recovery-related outcomes in individuals following severe COVID-19 using an explanatory mixed-methods design. Thirtynine patients were assessed at hospital discharge and after 8 weeks of unsupervised rehabilitation in a single-centre prospective cohort study conducted in Slovenia (ClinicalTrials.gov: NCT04860206, https://clinicaltrials.gov/study/NCT04860206). Results: Quantitative analyses showed a significant increase in fat-free mass over time and positive associations between fat-free mass and adherence to the Mediterranean diet. Qualitative findings further revealed that individuals with higher adherence demonstrated structured routines, adaptive coping strategies, and greater psychosocial resilience during recovery. Discussion: Together, these findings suggest that adherence to a Mediterranean dietary pattern, alongside related lifestyle behaviors, may support favorable body composition and enhance recovery processes following severe illness. This study provides an integrated perspective on physiological and behavioral determinants of recovery, highlighting the potential of nutrition-based approaches in post- COVID-19 rehabilitation.
Ključne besede: body composition, clinical nutrition, COVID-19 rehabilitacija, dietary patterns, lifestyle factors, Mediterranean diet, mixed-methods, rehabilitation
Objavljeno v DiRROS: 30.06.2026; Ogledov: 263; Prenosov: 206
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4. Changes in gait and postural control after 10-day bed rest and 30-day recovery : Elektronski virLuka Šlosar, Manca Peskar, Boštjan Šimunič, Rado Pišot, Marco Vincenzo Narici, Uroš Marušič, 2026, izvirni znanstveni članek Povzetek: Background Prolonged bed rest is a well-established model for studying the effects of immobility on functional performance, especially gait and postural control. Understanding how these functions deteriorate and recover across age groups is essential for developing targeted rehabilitation strategies. Research question How does a 10-day horizontal bed rest affect gait performance and postural control in young and older adults, and to what extent do these effects differ by age? Methods Following a multistage screening process from a large pool of healthy male volunteers, ten older men (68.5 ± 2.6 years) and ten young men (22.9 ± 4.7 years) completed 10 days of horizontal bed rest in a controlled laboratory setting, followed by a standardized 30-day recovery program. Postural control and gait speed assessed under self-selected and brisk walking conditions were measured before bed rest, immediately after, and following a 30-day recovery program. Results Following bed rest, self-selected walking speed did not differ significantly from baseline in either group. In contrast, brisk walking speed significantly decreased in older (−11.4%, p < 0.05) and young adults (−9.9%, p < 0.05), with both groups returning to baseline values after recovery. Postural control deteriorated significantly in older adults (-15.5%), whereas no significant difference from baseline was observed in young adults. After baseline adjustment, postural control showed a significant group effect both after bed rest (η² > 0.244) and post-recovery (η² > 0.395). Significance The findings reveal clear age-related differences in responses to inactivity and recovery. Older adults experienced greater impairments and slower restoration of balance, indicating heightened vulnerability to functional decline during periods of immobilization. These findings underscore the age-dependent impact of bed rest and the importance of tailored rehabilitation strategies.
Ključne besede: aging, physical inactivity, mobile body imaging, functional decline
Objavljeno v DiRROS: 24.04.2026; Ogledov: 472; Prenosov: 457
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5. Mental - and temporal - demand NASA - task load Index scores correlate with decreases in irisin serum levels in healthy individuals subjected to 10-day bed restPatrizia Pignataro, Uroš Marušič, Roberta Zerlotin, Angela Oranger, Manuela Dicarlo, Clelia Suriano, Paolo Taurisano, Rado Pišot, Boštjan Šimunič, Marco Vincenzo Narici, 2026, izvirni znanstveni članek Povzetek: Background Bed rest (BR) is a widely used analogue of space flight that aims to replicate microgravity conditions, such as immobilization and a lack of sensorimotor stimuli. In a previous BR study, we evaluated the changes in irisin serum levels, a myokine produced mainly by skeletal muscle that exerts pleiotropic effects on several organs, including the brain. Objective Here, we evaluated whether the decline in circulating irisin concentrations during 10 days of horizontal BR correlated with the National Aeronautics and Space Administration Task Load Index (NASA-TLX). Methods NASA-TLX was obtained from young healthy participants at the end of the BR protocol. It is a self-report measure of task load that includes six subscales: mental demand, physical demand, temporal demand, performance, effort, and frustration. Each subscale score was correlated with the decline in serum irisin levels measured while participants were supine. Irisin decline was calculated as the difference between levels on the first day of BR (BR0) and the last day (BR9). Results Our results show a significant positive correlation between irisin decline and both mental demand and temporal demand, whereas correlations with the remaining subscales showed a positive association with irisin decline but did not reach statistical significance. Conclusion These findings suggest that reduced irisin levels are associated with increased perceived mental demand and time pressure (temporal demand) during BR. Because temporal demand can exacerbate high mental activity in a state of cognitive overload, maintaining higher circulating irisin levels could represent an effective countermeasure to improve the cognitive performance of participants during future BR studies and may help astronauts manage mental and temporal pressure during space missions.
Ključne besede: bed rest, microgravity, irisin, cognitive performance, NASA-TLX indeks
Objavljeno v DiRROS: 09.04.2026; Ogledov: 323; Prenosov: 225
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6. The application of ultrasound sarcopenia index in sarcopenic populationKatarina Puš, Fabio Sarto, Marco Vincenzo Narici, Boštjan Šimunič, 2026, izvirni znanstveni članek Povzetek: Background: Aging leads to progressive motor system decline, which can result in sarcopenia, defined as the age- related loss of muscle mass and function. Architectural changes, epitomized by a decrease in fascicle length (Lf) and muscle thickness (MT), provide a useful signature of sarcopenia. Their ratio (Lf/MT), named ultrasound sarcopenia index (USI), is a new parameter proposed for evaluating changes in muscle geometric proportions associated with muscle atrophy but lacks application in a sarcopenic population. This study aimed to explore vastus lateralis USI in a sarcopenic population. Methods: In a sample of 139 older adults (54% females), recruited from Italy and Slovenia, we assessed muscle architecture using ultrasound imaging to measure Lf, MT, pennation angle (PA), and USI. We assessed handgrip strength, sit-to-stand test, and physical performance with timed up-and-go and gait speed. Appendicular lean mass was assessed with dual x-ray absorptiometry. Sarcopenia was classified using the EWGSOP2 and SDOC classifications. Results: Sarcopenia prevalence was 15.1% and 30.9% when classified by the EWGSOP2 and SDOC classifications, respectively. Differences in muscle architecture were observed between sarcopenic and non-sarcopenic groups, with MT showing the largest effect size (Cohen's d EWGSOP2: 0.86; SDOC:0.77). USI was higher in sarcopenic compared to non-sarcopenic individuals classified with EWGSOP2 (5.33 ± 1.30 vs 4.59 ± 0.94, p = .011, Cohen's d:0.69), confirming its sensitivity in detecting sarcopenia. Conclusion: We showed that increased USI values are associated with sarcopenia. This study shows USI as a sensitive, non-invasive marker for sarcopenia classification, supporting its use in clinical screening and monitoring of muscle changes in older adults.
Ključne besede: muscle architecture, aging, muscle quality, muscle function
Objavljeno v DiRROS: 26.03.2026; Ogledov: 435; Prenosov: 321
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7. Association between TMG-derived contractile muscle parameters and MRI-based muscle structure in sarcopeniaKatarina Puš, D. A. Madrid Fuentes, Ashley Weaver, Miloš Kalc, Jeannette R. Mahoney, Boštjan Šimunič, 2026, izvirni znanstveni članek Povzetek: Background: Muscle fat fraction (MFF) obtained through magnetic resonance imaging (MRI) is the gold standard for assessing muscle quality, but it is expensive and time consuming. Portable methods to examine muscles such as tensiomyography (TMG) are emerging and could enable broader screening. This study aims to examine associations between TMG-derived muscle contractile parameters and MFF in older adults with and without sarcopenia. Methods: A sample of 51 Slovenian older adults (53% females) were scanned with Dixon MRIs to evaluate muscle MFF and contractile parameters were assessed with TMG estimating delay time (Td), maximal displacement (Dm) and radial contraction velocity (Vc). Right leg vastus lateralis (VL) and biceps femoris (BF) were analyzed. Sarcopenia was defined using both European Working Group on Sarcopenia in Older People (EWGSOP2) and Sarcopenia Definition and Outcomes Consortium (SDOC) criteria. Regression models adjusted for age and sex were used to assess associations between TMG-derived contractile parameters and MFF. Results: Age- and sex-adjusted models revealed associations between increased MFF and reduced Dm (R2 = .29, p = .003) and Vc (R2 = .32, p = .002) for the VL. SDOC-classified sarcopenic individuals showed increased VL MFF (27.2% vs 22.5%, p = .019),while EWGSOP2 classified sarcopenia displayed no differences. Discussion: The study reveals that increased MFF is associated with reduced muscle contractility in VL. MFF differs between sarcopenic and non-sarcopenic groups using only SDOC criteria. Since the TMG Dm increase is regularly found in atrophic muscles after bed rest, in sarcopenic muscle MFF explains lowering of the Dm, highlighting the TMG potential for early detection of changes in aging muscle.
Ključne besede: sarcopenia, contractile parameters, tensiomyography, muscle fat fraction, muscle function, older adults
Objavljeno v DiRROS: 23.03.2026; Ogledov: 417; Prenosov: 337
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8. Tensiomyography-derived contractile parameters in sarcopenic and non-sarcopenic older adultsKatarina Puš, Miloš Kalc, Boštjan Šimunič, 2026, izvirni znanstveni članek Povzetek: Background: Sarcopenia, the progressive decline in skeletal muscle mass and function, is a major public health concern linked to falls, hospitalization and loss of independence among older adults. Initially defined by reduced muscle mass, later also by reduced muscle strength and function, it is now recognized that standard diagnostic tools do not fully capture complexity of sarcopenia. Tensiomyography (TMG) is a non-invasive method that assesses skeletal muscle contractile parameters, which undergo change with aging and sarcopenia. The aims of this exploratory study are to determine whether TMG could be a method for contractile parameters assessment in sarcopenia classification and to evaluate the relationship between TMG-derived parameters and sarcopenia classification tests. Methods: We included 654 older adults (70.6% women) and included demographics, sarcopenia classification (EWGSOP2, SDOC), muscle strength (handgrip strength, five sit-to-stand), TMG of three leg muscles, muscle mass (bioimpedance), and physical performance (gait speed, timed up-and-go). MANOVA was used to analyze contractile properties and due to low agreement between classifications, we used both classifications. A partial correlation for each sex was conducted to determine the associations between sarcopenia classification tests and TMG-derived parameters of delay time (Td), contraction time (Tc), radial displacement (Dm) and contraction velocity (Vc), controlling for age. Results: One-way MANOVA confirmed difference between sarcopenic and nonsarcopenic participants according to EWGSOP2 and SDOC classifications in TMG-derived contractile parameters in all three muscles, Td was consistently longer and Dm consistently lower in sarcopenic individuals. Post-hoc univariate tests further demonstrated specific differences due to sarcopenia presence. Ageadjusted partial correlations were weak to moderate, ranging between −0.430 and 0.369. Conclusion: Sarcopenic individuals exhibited longer Td and Tc, and smaller Dm, though not consistently across all muscles. Td was longer in all three muscles, reflecting electromechnical delays linked to aging. Dm was consistently lower, suggesting increased muscle stiffness. Correlations between TMG parameters and sarcopenia classification tests indicated that shorter Td and Tc, higher Dm, and greater Vc were associated with higher muscle volume, muscle strength and performance. The findings indicate that TMG parameters may be associated with neuromuscular degeneration and sarcopenia, supporting further exploration of muscle- and sex-specific differences.
Ključne besede: tensiomyography, muscle function, older adults, sarcopenia, seniors
Objavljeno v DiRROS: 04.02.2026; Ogledov: 797; Prenosov: 378
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9. Prevalenca sarkopenije in povezani dejavniki tveganja v Sloveniji : raziskovalni podatki, obravnavani v doktorskem deluKatarina Puš, Miloš Kalc, Saša Pišot, Kaja Teraž, Jure Urbanc, Matej Kleva, Uroš Marušič, Manca Peskar, Luka Šlosar, Boštjan Šimunič, 2026, raziskovalni podatki Povzetek: Podatkovni niz vsebuje anonimizirane presečne podatke, zbrane pri 654 starejših odraslih (≥ 60 let) iz Slovenije. Podatki so bili pridobljeni v okviru presečne raziskave, usmerjene v razvrščanje sarkopenije in analizo mišičnih značilnosti. V podatkovni niz so vključeni demografski podatki (starost, spol), antropometrične meritve ter rezultati meritev mišične jakosti, telesne zmogljivosti in telesne sestave. Mišična jakost je bila ocenjena z merjenjem jakosti stiska pesti in testom petkratnega vstajanja s stola. Telesna zmogljivost je bila ocenjena s hitrostjo hoje in testom vstani in pojdi. Podatki o telesni sestavi in mišični masi so bili pridobljeni z električno bioimpedančno analizo in vključujejo pusto telesno maso, skeletno mišično maso, apendikularno skeletno mišično maso ter indekse, prilagojene telesni višini. Kontraktilne lastnosti skeletnih mišic so bile ocenjene s tenziomiografijo treh mišic spodnjih okončin, pri čemer so bili zabeleženi parametri zakasnitvenega časa, časa kontrakcije, radialnega premika in hitrosti kontrakcije. Dodatni podatki vključujejo prehransko stanje (Mini Nutritional Assessment), gibalno aktivnost in sedentarne navade (Global Physical Activity Questionnaire) ter kognitivne funkcije (Test povezovanja – del A in B). Preiskovanci so bili razvrščeni v skupine glede na več diagnostičnih algoritmov sarkopenije (EWGSOP, EWGSOP2 in njegove različice, SDOC, IWGS in FNIH). Podatki so bili zbrani po standardiziranih protokolih, anonimizirani in opremljeni z metapodatki, kar omogoča njihovo ponovno uporabo v skladu z načeli FAIR.
Ključne besede: sarkopenija, analiza mišičnih značilnost, mišična jakost, telesna sestava, telesna zmogljivost, telesna masa, gibalna aktivnost, sedentarne navade
Objavljeno v DiRROS: 03.02.2026; Ogledov: 595; Prenosov: 551
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