1. 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: 197; Downloads: 66
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2. Prevalence of sarcopenia among Slovenian older adults and associated risk factorsKatarina Puš, Saša Pišot, Uroš Marušič, Manca Peskar, Kaja Teraž, Miloš Kalc, Helena Blažun Vošner, Peter Kokol, Jernej Završnik, Boštjan Šimunič, 2025, original scientific article Abstract: Introduction: Sarcopenia is a multifaceted condition affecting between 10 and 16% of the global population, and although multiple classification algorithms exist, no prevalence has been reported for a representative sample of the Slovenian population. Furthermore, multiple behavioural factors, such as malnutrition, physical inactivity, sedentary lifestyle and lower cognitive function, can contribute to the risk of sarcopenia. This study aims to: a) determine sarcopenia prevalence among Slovenian older adults according to different classification algorithms, b) compare the agreement among the algorithms and c) evaluate the relationship between proposed risk factors and sarcopenia. Methods: 654 participants (≥60 years, 30.4% males) have been classified into sarcopenia groups according to eight algorithms, and agreement (Fleiss K) between them was calculated. Additionally, age, sex, nutritional status, physical activity, sedentary levels and cognitive function were assessed as sarcopenia risk/protective factors. Results: The prevalence of sarcopenia according to EWGSOP2 was 4.1%, ranging from 2.1% to 15.3%, when classified by all eight algorithms. Overall agreement between algorithms was weak (K=.429; 95% CI .414 to .444) with 0.6% of participants classified as sarcopenic by all eight algorithms. Adequate nutrition and physical activity were identified as protective factors, while age, lower cognitive function and sedentary lifestyle were considered risk factors. Conclusion: Sarcopenia prevalence among the Slovenian general population was lower than in the global population. We can conclude that different sarcopenia algorithms lead to a different prevalence of sarcopenia. It is of great importance to be cautious when comparing prevalences among studies and to further validate the classification algorithms.
Keywords: sarcopenia, prevalence, epidemiology, classification algorithms, risk factors
Published in DiRROS: 03.03.2025; Views: 229; Downloads: 109
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3. Cortico-muscular phase connectivity during an isometric knee extension task in people with early Parkinson’s diseaseNina Omejc, Tomislav Stankovski, Manca Peskar, Miloš Kalc, Paolo Manganotti, Klaus Gramann, Sašo Džeroski, Uroš Marušič, 2025, original scientific article Abstract: — Introduction: Parkinson’s disease (PD) is characterized by enhanced beta-band activity (13–30 Hz) in the motor control regions. Simultaneously, corticomuscular (CM) connectivity in the beta-band during isometric contractions tends to decline with age, in various diseases, and under dual-task conditions. Objective: This study aimed to characterize electroencephalograph (EEG) and electromyograph (EMG) power spectra during a motor task, assess CM phase connectivity, and explore how these measures are modulated by an additional cognitive task. Specifically, we focused on the beta-band to explore the relationship between heightened beta amplitude and reduced beta CM connectivity. Methodology: Early-stage people with PD and age-matched controls performed an isometric knee extension task, a cognitive task, and a combined dual task, while EEG (128ch) and EMG (2x32ch) were recorded. CM phase connectivity was assessed through phase coherence and a phase dynamics model. Results: The EEG power spectrum revealed no cohort differences in the beta-band. EMG also showed no differences up to 80 Hz. However, the combined EEG-EMG analysis uncovered reduced beta phase coherence in people with early PD during the motor task. CM phase coherence exhibited distinct scalp topography and frequency ranges compared to the EEG power spectrum, suggesting different mechanisms for pathological beta increase and CM connectivity. Additionally, phase dynamics modelling indicated stronger directional coupling from the cortex to the active muscle and less prominent phase coupling across people with PD. Despite high inter-individual variability, these metrics may prove useful for personalized assessments, particularly in people with heightened CM connectivity.
Keywords: electroencephalography, brain modeling, electromiography, coherence, motors, diseases, couplings, electrodes, oscillators, protocols
Published in DiRROS: 13.01.2025; Views: 340; Downloads: 184
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4. Acute myotonometric changes in the masseter and upper trapezius muscles after upper body quarter stretching and coordination exercises or chewingMarša Magdič, Miloš Kalc, Matjaž Vogrin, 2025, original scientific article Abstract: Pathologies in neck and masticatory muscles affect muscle tone and biomechanical and viscoelastic properties, necessitating precise assessment for treatment. This study evaluated the impact of two guided interventions—relaxing exercises targeting the neck and masticatory muscles (“Exercise”) and heavy chewing using six chewing gums (“Chewing”)—on the masseter and upper trapezius muscles. Twelve participants (aged 19–40 years) underwent myotonometric assessment pre- and post-intervention, measuring tone, stiffness, decrement, relaxation time, and creep. The results showed significant changes in the masseter muscle after exercise, with increased stiffness (14.46%, p < 0.001) and tone (7.03%, p < 0.001) but decreased creep (−9.71%, p < 0.001) and relaxation time (−11.36%, p < 0.001). Conversely, chewing decreased stiffness (−8.82%, p < 0.001) and tone (−5.53%, p < 0.001), while it increased creep (9.68%, p < 0.001) and relaxation time (9.98%, p < 0.001). In the trapezius muscles, tone decreased after both interventions (Exercise: −7.65%, p < 0.001; Chewing: −1.06%, p = 0.003), while relaxation increased (Exercise: 1.78%, p < 0.001; Chewing: 2.82%, p < 0.001). These findings reveal the distinct effects of exercise and chewing on muscle properties, emphasising the complexity of their therapeutic potential and the need for further investigation.
Keywords: muscle tonus, relaxation, masseter muscle, trapezius muscle, intervention studies
Published in DiRROS: 07.01.2025; Views: 317; Downloads: 186
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5. The effectiveness of neuromuscular training warm-up program for injury preventionin adolescent male basketball playersArmin Paravlić, Peter Bakalár, Katarina Puš, Saša Pišot, Miloš Kalc, Kaja Teraž, Luka Šlosar, Manca Peskar, Uroš Marušič, Boštjan Šimunič, 2024, original scientific article Abstract: This study evaluated the effects of a neuromuscular training (NMT) warm-up program on injury incidence,neuromuscular function, and program adherence, maintenance and acceptance in adolescent basketballplayers. A total of 275 players from 20 Slovenian teams (15 ± 1.7 years of age), were randomized into anintervention group (IG, n=129) and a control group (CG, n=146). Over three months, the IG incorporatedNMT into their warm-ups, while the CG followed their usual practice. Measurements of body anthro-pometry, muscle contractile properties, and balance were taken before and after the intervention. Also,the injury incidence, training adherence and maintenance were reported. Both groups showed improvedbalance, with no significant difference between them. However, IG demonstrated reduced delay times inspecific muscles, indicating improved neuromuscular function. Injury prevalence proportion (%) duringthe whole study period was higher in the control group compared to intervention (IG: 10.9% vs. CG:23.3%), and incidence rate. Moreover, the incidence rate ratio for sustaining an injury was 2.6 on average(ranging from 0.88 to 7.07 for tendon and muscle injuries, respectively), indicating significantly lowerinjury risk in IG than CG. These findings highlight the effectiveness of NMT warm-ups in reducing injuryrisk and enhancing neuromuscular function, emphasizing the value of structured injury preventionstrategies in youth sports.
Keywords: muscle contractile properties, balance, injury prevalence, training adherence
Published in DiRROS: 18.11.2024; Views: 436; Downloads: 219
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6. Participation in youth sports influences sarcopenia parameters in older adultsKaja Teraž, Miloš Kalc, Boštjan Šimunič, Uroš Marušič, Primož Pori, Saša Pišot, Rado Pišot, 2023, original scientific article Abstract: Background The degree of deterioration in sarcopenia parameters may be affected by a person’s level of physical activity (PA) and sedentary behavior (SB). Our study focused on examining the PA and SB of active older adults including those with and without history of sports in youth. Methods Forty-four participants (20 men and 24 women, mean age of total sample 76.1 ± 5.2 years) were included in analysis of PA, SB habits and sarcopenia parameters, determined by skeletal muscle index, hand-grip strength, gait speed, Timed Up and Go tests (TUG). PA and SB were recorded with accelerometers. Our primary aim was to compare participants with (AH) or without a sport history in youth (NAH), in their sarcopenia parameters and PA and SB habits. Results When divided participants in two groups (AH and NAH) and adjusting for age, we have detected the differences for skeletal muscle index (p = 0.007) and hand-grip strength (p = 0.004) in favor of participants who were engaged in sports in youth. We did not find any differences in PA and SB habits between the AH and NAH groups. After adjusting for age, participants with a higher number of daily steps, longer moderate to vigorous physical activity (MVPA) bouts, a higher number of MVPA bouts in a day and higher overall MVPA engagement achieved better results in hand-grip strength and TUG. Participants with lower SB had better TUG and gait speed results. Conclusions Our findings suggest that engaging in sports activities in youth can make a difference with sarcopenia parameters. Although we found no differences in PA and SB habits between participants with AH and NAH, participants with an athlete history performed better results in sarcopenia parameters.
Keywords: muscles, muscle disorder, elderly, exercise, sedentarism
Published in DiRROS: 10.11.2023; Views: 987; Downloads: 2525
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7. Neuromuscular assessment of force development, postural, and gait performance under cognitive-motor dual-tasking in healthy older adults and early Parkinson's disease patients : study protocol for a cross-sectional Mobile Brain/Body Imaging (MoBI) studyUroš Marušič, Manca Peskar, Maja Maša Šömen, Miloš Kalc, Aleš Holobar, Klaus Gramann, Bettina Wollesen, Anna Wunderlich, Christoph M. Michel, Aleksandar Miladinović, Mauro Catalan, Alex B. Stella, Miloš Ajčević, Paolo Manganotti, 2023, original scientific article Abstract: Background: Neuromuscular dysfunction is common in older adults and more pronounced in neurodegenerative diseases. In Parkinson's disease (PD), a complex set of factors often prevents the effective performance of activities of daily living that require intact and simultaneous performance of the motor and cognitive tasks. Methods: The cross-sectional study includes a multifactorial mixed-measure design. Between-subject factor grouping the sample will be Parkinson’s Disease (early PD vs. healthy). The within-subject factors will be the task complexity (single- vs. dual-task) in each motor activity, i.e., overground walking, semi-tandem stance, and isometric knee extension, and a walking condition (wide vs. narrow lane) will be implemented for the overground walking activity only. To study dual-task (DT) effects, in each motor activity participants will be given a secondary cognitive task, i.e., a visual discrimination task for the overground walking, an attention task for the semi-tandem, and mental arithmetic for the isometric extension. Analyses of DT effects and underlying neuronal correlates will focus on both gait and cognitive performance where applicable. Based on an a priori sample size calculation, a total N = 42 older adults (55-75 years) will be recruited. Disease-specific changes such as laterality in motor unit behavior and cortical control of movement will be studied with high-density surface electromyography and electroencephalography during static and dynamic motor activities, together with whole-body kinematics. Discussion: This study will be one of the first to holistically address early PD neurophysiological and neuromuscular patterns in an ecologically valid environment under cognitive-motor DT conditions of different complexities. The outcomes of the study aim to identify the biomarker for early PD either at the electrophysiological, muscular or kinematic level or in the communication between these systems.
Keywords: Parkinson's disease, mobile brain imaging, body brain imaging, MoBi, dual tasking, neuromuscular function, older adults
Published in DiRROS: 15.09.2023; Views: 1118; Downloads: 509
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8. Diagnostic accuracy of tensiomyography parameters for monitoring peripheral neuromuscular fatigueMiloš Kalc, Katarina Puš, Armin Paravlić, Jure Urbanc, Boštjan Šimunič, 2023, original scientific article Abstract: The diagnostic accuracy of tensiomyography (TMG) parameters compared to the gold standard in neuromuscular fatigue evaluation using voluntary and electrically induced muscle activation is unclear. This study aimed to investigate the diagnostic accuracy of TMG parameters to detect individual changes after interventions that were designed to induce central or peripheral fatigue. Nineteen males (age: 32.2 ± 9.3 years) performed two interventions, consisting of maintaining 25% of maximal voluntary contraction (MViC25%) and a 30 s all-out cycling test (Wingate), respectively. TMG parameters, maximum voluntary contraction (PtMViC), voluntary activation (VA%) and electrically elicited double twitches (Dtw) were assessed on the knee extensors before (PRE), one minute (POST) and seven minutes after (POST7) the intervention. The diagnostic accuracy (AUC) of TMG parameters were evaluated in comparison to two criteria measures (PtMViC and Dtw). RM ANOVA revealed a significant interaction between the effects of intervention and time on VA% (p = 0.001) and Dtw (p < 0.001) but not for PtMViC (p = 0.420). AUC showed that TMG parameters had a good ability in detecting muscular fatigue assessed by Dtw but not by PtMViC. The results of the current study suggest that TMG parameters can be used to monitor peripheral neuromuscular fatigue.
Keywords: tensiomyography, vastus lateralis, MVC, twitch
Published in DiRROS: 13.06.2023; Views: 963; Downloads: 522
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9. Sarcopenia parameters in active older adults – an eight-year longitudinal studyKaja Teraž, Uroš Marušič, Miloš Kalc, Boštjan Šimunič, Primož Pori, Bruno Grassi, Stefano Lazzer, Marco Vincenzo Narici, Mojca Gabrijelčič Blenkuš, Pietro Enrico Di Prampero, Carlo Reggiani, Angelina Passaro, Gianni Biolo, Mladen Gasparini, Rado Pišot, 2023, original scientific article Abstract: Background Sarcopenia is a common skeletal muscle syndrome that is common in older adults but can be mitigated by adequate and regular physical activity. The development and severity of sarcopenia is favored by several factors, the most influential of which are a sedentary lifestyle and physical inactivity. The aim of this observational longitudinal cohort study was to evaluate changes in sarcopenia parameters, based on the EWGSOP2 definition in a population of active older adults after eight years. It was hypothesized that selected active older adults would perform better on sarcopenia tests than the average population. Methods The 52 active older adults (22 men and 30 women, mean age: 68.4±5.6 years at the time of their first evaluation) participated in the study at two time points eight-years apart. Three sarcopenia parameters were assessed at both time points: Muscle strength (handgrip test), skeletal muscle mass index, and physical performance (gait speed), these parameters were used to diagnose sarcop0enia according to the EWGSOP2 definition. Additional motor tests were also performed at follow-up measurements to assess participants’ overall fitness. Participants self-reported physical activity and sedentary behavior using General Physical Activity Questionnaire at baseline and at follow-up measurements. Results In the first measurements we did not detect signs of sarcopenia in any individual, but after 8 years, we detected signs of sarcopenia in 7 participants. After eight years, we detected decline in ; muscle strength (-10.2%; p<.001), muscle mass index (-5.4%; p<.001), and physical performance measured with gait speed (-28.6%; p<.001). Similarly, self-reported physical activity and sedentary behavior declined, too (-25.0%; p=.030 and −48.5%; p<.001, respectively). Conclusions Despite expected lower scores on tests of sarcopenia parameters due to age-related decline, participants performed better on motor tests than reported in similar studies. Nevertheless, the prevalence of sarcopenia was consistent with most of the published literature. Trial registration The clinical trial protocol was registered on ClinicalTrials.gov, identifier: NCT04899531
Keywords: elderly, physical activities, sedentary behavior, skeletal muscle disorder, sarcopenia
Published in DiRROS: 29.05.2023; Views: 954; Downloads: 513
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10. Sarcopenia, obesity, and their association with selected behavioral factors in active older adultsKaja Teraž, Miloš Kalc, Manca Peskar, Saša Pišot, Boštjan Šimunič, Rado Pišot, Primož Pori, 2023, original scientific article Abstract: Introduction: The number of obese people in the world is increasing, as is the number of sarcopenic people among the older adults. Although both states are concerning, they can be positively influenced by selected behavioral factors such as adequate nutrition and physical activity. We were interested in the prevalence of sarcopenic obesity in active older people and the influence of behavioral factors on this phenomenon. Methods: The study included 38 older adults (21 women) with a mean age of 75.3 ± 5.0 years. Sarcopenic parameters were determined with different tests: Handgrip Test, Chair Stand Test, Gait Speed, Timed Up and Go Test, and Short Physical Performance Battery. Body composition was measured by dual-energy x-ray absorptiometry. Physical activity level was measured using accelerometers, and nutritional status was assessed using the Mini-Nutritional Assessment and MEDLIFE Index questionnaire. Results: Of all included active participants (the average number of steps per day was 8,916 ± 3,543), 47.4% of them were obese. Of all included women, 52.4% were obese. Sarcopenic obesity was found in three (7.9%) participants. Nutritional status correlated with strength of lower extremities and physical performance tests (gait speed, Timed Up and Go Test and Short Physical performance battery). Higher number of steps per day positively correlates with physical performance. Discussion: Interestingly, we did not find any correlation between the main obesity parameter such as percent body fat or body mass index (and thus sarcopenic obesity) and any of the selected behavioral factors (physical activity, sedentary behavior, or dietary habits). In conclusion, reaching the recommended levels of physical activity in older adults may not be sufficient to prevent the occurrence of obesity and sarcopenic obesity.
Keywords: aging, physical activity, nutrition, healthy lifestyle, body composition, sarcopenia
Published in DiRROS: 02.03.2023; Views: 1262; Downloads: 613
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