| 1. |
- Alkner, Björn A, et al.
(author)
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Knee extensor and plantar flexor muscle size and function following 90 days of bed rest with or without resistance exercise.
- 2004
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In: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 93:3, s. 294-305
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Journal article (peer-reviewed)abstract
- Skeletal muscle atrophy and strength loss induced by short-term simulated spaceflight are offset or attenuated by resistance exercise (RE). This study compared the effects of plantar flexor and knee extensor RE on muscle size and function in 17 healthy men (aged 26–41years) subjected to 90 days 6 head-down-tilt bed rest with (BRE; n=8) or without (BR; n=9) RE. The RE program consisted of coupled maximal concentric and eccentric actions in the supine squat (4 sets of 7 repetitions) and calf press (4·14) every third day employing a gravity-independent flywheel ergometer (FW). Prior to, and following bed rest, muscle volume was assessed using magnetic resonance imaging. Similarly, muscle strength and power and surface lectromyographic (EMG) activity were determined during maximal actions using FW or isokinetic dynamometry. In BR, knee extensor and plantar flexor muscle volume decreased (P<0.05) 18% and 29%, respectively. Torque or force and power decreased (P<0.05) 31–60% (knee extension) and 37–56% (plantar flexion) while knee extensor and plantar flexor EMG activity decreased 31–38% and 28–35%, respectively following BR. Muscle atrophy in BRE was prevented (P>0.05; knee extensors) or attenuated ()15%; plantar flexors). BRE maintained task-specific force, power and EMG activity. The decrease in non-task-specific torque was less (P<0.05) than in BR. The present data imply that the triceps surae and quadriceps muscles show different responsiveness to long-term bed rest with or without resistance exercise. The results also suggest that designing in-flight resistance exercise protocols for space travellers is complex and must extend beyond preserving
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| 2. |
- Figueiredo, Vandre C., et al.
(author)
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Genetic and epigenetic regulation of skeletal muscle ribosome biogenesis with exercise
- 2021
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In: Journal of Physiology. - : Wiley-Blackwell. - 0022-3751 .- 1469-7793. ; 599:13, s. 3363-3384
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Journal article (peer-reviewed)abstract
- Key points Ribosome biogenesis and MYC transcription are associated with acute resistance exercise (RE) and are distinct from endurance exercise in human skeletal muscle throughout a 24 h time course of recovery. A PCR-based method for relative ribosomal DNA (rDNA) copy number estimation was validated by whole genome sequencing and revealed that rDNA dosage is positively correlated with ribosome biogenesis in response to RE. Acute RE modifies rDNA methylation patterns in enhancer, intergenic spacer and non-canonical MYC-associated regions, but not the promoter. Myonuclear-specific rDNA methylation patterns with acute mechanical overload in mice corroborate and expand on rDNA findings with RE in humans. A genetic predisposition for hypertrophic responsiveness may exist based on rDNA gene dosage. Ribosomes are the macromolecular engines of protein synthesis. Skeletal muscle ribosome biogenesis is stimulated by exercise, although the contribution of ribosomal DNA (rDNA) copy number and methylation to exercise-induced rDNA transcription is unclear. To investigate the genetic and epigenetic regulation of ribosome biogenesis with exercise, a time course of skeletal muscle biopsies was obtained from 30 participants (18 men and 12 women; 31 +/- 8 years, 25 +/- 4 kg m(-2)) at rest and 30 min, 3 h, 8 h and 24 h after acute endurance (n = 10, 45 min cycling, 70% V?O2max) or resistance exercise (n = 10, 4 x 7 x 2 exercises); 10 control participants underwent biopsies without exercise. rDNA transcription and dosage were assessed using quantitative PCR and whole genome sequencing. rDNA promoter methylation was investigated using massARRAY EpiTYPER and global rDNA CpG methylation was assessed using reduced-representation bisulphite sequencing. Ribosome biogenesis and MYC transcription were associated primarily with resistance but not endurance exercise, indicating preferential up-regulation during hypertrophic processes. With resistance exercise, ribosome biogenesis was associated with rDNA gene dosage, as well as epigenetic changes in enhancer and non-canonical MYC-associated areas in rDNA, but not the promoter. A mouse model of in vivo metabolic RNA labelling and genetic myonuclear fluorescence labelling validated the effects of an acute hypertrophic stimulus on ribosome biogenesis and Myc transcription, and also corroborated rDNA enhancer and Myc-associated methylation alterations specifically in myonuclei. The present study provides the first information on skeletal muscle genetic and rDNA gene-wide epigenetic regulation of ribosome biogenesis in response to exercise, revealing novel roles for rDNA dosage and CpG methylation.
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| 3. |
- Alkner, Björn, et al.
(author)
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Efficacy of a gravity-independent resistance exercise device as a countermeasure to muscle atrophy during 29-day bed rest.
- 2004
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In: Acta Physioloogica Scandinavica. - 0001-6772. ; 181:3, s. 345-357
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Journal article (peer-reviewed)abstract
- This study determined changes in knee extensor and plantar flexor muscle volume during 29 days of bed rest with or without resistance exercise using a gravity-independent flywheel ergometer. METHODS: Seventeen men (26-41 years) were subjected to 29 days of bed rest with (n = 8) or without (n = 9) resistance exercise; Supine Squat (SS) and Calf Press (CP) performed every third day. Quadriceps and triceps surae muscle volume was determined before and after bed rest and force and power were measured during training. Prior to these interventions, reproducibility of this device for training and testing was assessed in 23 subjects who performed bilateral maximal concentric, eccentric and isometric (MVC) knee extensions and plantar flexions over repeated sessions with simultaneous measurements of force, power and electromyographic (EMG) activity. RESULTS: Quadriceps and triceps surae muscle volume decreased (P < 0.05) 10 and 16%, respectively, after 29 days bed rest. Exercise maintained quadriceps volume and mitigated triceps surae atrophy. Thus, either muscle showed different response across subject groups (P < 0.05). Force and power output during training were either maintained (P > 0.05) or increased (P < 0.05). EMG amplitude in the training mode was similar (SS; P > 0.05) or greater (CP; P < 0.05) compared with that elicited during MVC. Peak force and power test-retest coefficient of variation (CV) ranged 5-6% and 7-8% for SS and CP, respectively. CONCLUSION: The present data suggest that this resistance exercise paradigm counteracts quadriceps and abates the more substantial triceps surae muscle atrophy in bedridden subjects, and therefore should be an important asset to space travellers.
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| 4. |
- Beato, Marco, et al.
(author)
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Current Guidelines for the Implementation of Flywheel Resistance Training Technology in Sports: A Consensus Statement
- 2024
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In: Sports Medicine. - : ADIS INT LTD. - 0112-1642 .- 1179-2035.
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Research review (peer-reviewed)abstract
- BackgroundFlywheel resistance training has become more integrated within resistance training programs in a variety of sports due to the neuromuscular, strength, and task-specific enhancements reported with this training.ObjectiveThis paper aimed to present the consensus reached by internationally recognized experts during a meeting on current definitions and guidelines for the implementation of flywheel resistance training technology in sports.MethodsNineteen experts from different countries took part in the consensus process; 16 of them were present at the consensus meeting (18 May 2023) while three submitted their recommendations by e-mail. Prior to the meeting, evidence summaries were developed relating to areas of priority. This paper discusses the available evidence and consensus process from which recommendations were made regarding the appropriate use of flywheel resistance training technology in sports. The process to gain consensus had five steps: (1) performing a systematic review of systematic reviews, (2) updating the most recent umbrella review published on this topic, (3) first round discussion among a sample of the research group included in this consensus statement, (4) selection of research group members-process of the consensus meeting and formulation of the recommendations, and (5) the consensus process. The systematic analysis of the literature was performed to select the most up-to-date review papers available on the topic, which resulted in nine articles; their methodological quality was assessed according to AMSTAR 2 (Assessing the Methodological Quality of Systematic Review 2) and GRADE (Grading Recommendations Assessment Development and Evaluation). Statements and recommendations scoring 7-9 were considered appropriate.ResultsThe recommendations were based on the evidence summary and researchers' expertise; the consensus statement included three statements and seven recommendations for the use of flywheel resistance training technology. These statements and recommendations were anonymously voted on and qualitatively analyzed. The three statements reported a score ranging from 8.1 to 8.8, and therefore, all statements included in this consensus were considered appropriate. The recommendations (1-7) had a score ranging from 7.7 to 8.6, and therefore, all recommendations were considered appropriate.ConclusionsBecause of the consensus achieved among the experts in this project, it is suggested that practitioners and researchers should adopt the guidelines reported in this consensus statement regarding the use of flywheel resistance technology in sports.
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| 5. |
- Fernandez-Gonzalo, Rodrigo, et al.
(author)
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Three months of bed rest induce a residual transcriptomic signature resilient to resistance exercise countermeasures
- 2020
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In: The FASEB Journal. - : WILEY. - 0892-6638 .- 1530-6860. ; 34:6, s. 7958-7969
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Journal article (peer-reviewed)abstract
- This study explored the muscle genome-wide response to long-term unloading (84-day bed rest) in 21 men. We hypothesized that a part of the bed rest-induced gene expression signature would be resilient to a concurrent flywheel resistance exercise (RE) countermeasure. Using DNA microarray technology analyzing 35 345 gene-level probe-sets, we identified 335 annotated probe-sets that were downregulated, and 315 that were upregulated after bed rest (P < .01). Besides a predictable differential expression of genes and pathways related to mitochondria (downregulation; false-discovery rates (FDR) <1E-04), ubiquitin system (upregulation; FDR = 3E-02), and skeletal muscle energy metabolism and structure (downregulation; FDR <= 3E-03), 84-day bed rest also altered circadian rhythm regulation (upregulation; FDR = 3E-02). While most of the bed rest-induced changes were counteracted by RE, 209 transcripts were resilient to the exercise countermeasure. Genes upregulated after bed rest were particularly resistant to training (P < .001 vs downregulated, non-reversed genes). Specifically, "Translation Factors," "Proteasome Degradation," "Cell Cycle," and "Nucleotide Metabolism" pathways were not normalized by RE. This study provides an unbiased high-throughput transcriptomic signature of one of the longest unloading periods in humans to date. Classical disuse-related changes in structural and metabolic genes/pathways were identified, together with a novel upregulation of circadian rhythm transcripts. In the context of previous bed rest campaigns, the latter seemed to be related to the duration of unloading, suggesting the transcriptomic machinery continues to adapt throughout extended disuse periods. Despite that the RE training offset most of the bed rest-induced muscle-phenotypic and transcriptomic alterations, we contend that the human skeletal muscle also displays a residual transcriptomic signature of unloading that is resistant to an established exercise countermeasure.
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| 6. |
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| 7. |
- Pozzo, Marco, et al.
(author)
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Muscle-fiber conduction velocity during concentric and eccentric actions on a flywheel exercise device
- 2006
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In: Muscle and Nerve. - : Wiley. - 0148-639X .- 1097-4598. ; 34:2, s. 169-177
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Journal article (peer-reviewed)abstract
- A gravity-independent flywheel exercise device (FWED) has been proven effective as a countermeasure to loss of strength and muscle atrophy induced by simulated microgravity. This study assessed musclefiber conduction velocity (CV) and surface EMG instantaneous mean power spectral frequency (iMNF) during brief bouts of fatiguing concentric (CON) and eccentric (ECC) exercise on a FWED in order to identify electromyographic (EMG) variables that can be used to provide objective indications of muscle status when exercising with a FWED. Multichannel surface EMG signals were recorded from vastus lateralis and medialis muscles of nine men during: (1) isometric, 60-s action at 50% of maximum voluntary action (MVC); (2) two isometric, linearly increasing force ramps (0–100% MVC); and (3) dynamic CON/ECC coupled actions on the FWED. Muscle-fiber CV and iMNF were computed over time during the three tasks. During ramps, CV, but not iMNF, increased with force (P 0.001). Conduction velocity and iMNF decreased with the same normalized rate of change in constant-force actions. During CON/ECC actions, the normalized rate of change over time was larger for CV than iMNF (P 0.05). These results suggest that, during fatiguing, dynamic, variable-force tasks, changes in CV cannot be indirectly inferred by EMG spectral analysis. This underlines the importance of measuring both CV and spectral variables for muscle assessment in dynamic tasks.
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| 8. |
- Pozzo, Marco, et al.
(author)
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Muscle fiber conduction and fatigue during dynamic actions on a flywheel exercise device
- 2005
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In: Journal of Gravitational Physiology. - 1077-9248. ; 12:1, s. 113-114
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Journal article (peer-reviewed)abstract
- Exposure to microgravity has adverse effects on skeletal muscle size and function. Such effects can be counteracted by training using a Flywheel Exercise Device (FWED). Multichannel EMG signals were detected in nine males from vastus medialis and laterialis muscles during 30 coupled concentric (CON) and eccentric (ECC) actions on the FWED. Muscle fiber conduction velocity (CV) was assessed for each action. CV initial values depended on muscle action type (CON/ECC) and were higher in CON than ECC actions. CV decreased (P<0.05) over time during the task. Its slope was greater for VL than VM but was not different between CON and ECC. It was concluded that direct measure of CV is feasible during dynamic exercise, and that this technique may be used for objective assessment of the effect of resistance training in counteracting microgravity-induced muscle atrophy.
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| 9. |
- Rittweger, Jörn, et al.
(author)
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Muscle atrophy and bone loss after 90 days bed rest and the effects of flywheel resistive exercise and Pamidronate: Results from the LTBR study.
- 2005
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In: Bone. - : Elsevier BV. - 8756-3282 .- 1873-2763. ; 36:6, s. 1019-1029
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Journal article (peer-reviewed)abstract
- Muscle atrophy and bone loss pose substantial problems for long-term space flight and in clinical immobilization. We therefore tested the efficacy of flywheel resistive exercise and pamidronate to counteract such losses. Twenty five young healthy males underwent strict bed rest with 68 head-down tilt for 90 days. Subjects were randomized into an exercise group that practiced resistive exercise with a dflywheelT (FW) device every 2–3 days, a pamidronate group (Pam) that received 60 mg pamidronate i.v. 14 days prior to bed rest and a control group (Ctrl) that received none of these countermeasures. During the study, Ca++ and protein intake were controlled. Peripheral quantitative computed tomography (pQCT) was used to assess bone mineral content (BMC) and muscle cross sectional area (mCSA) of calf and forearm. Measurements were taken twice during baseline data collection, after 28 and after 89 days bed rest, and after 14 days recovery. On the same days, urinary Pyridinoline excretion and serum levels of alkaline phosphatase, Ca++ and PTH were measured. Pre-study exercise habits were assessed through the Freiburg questionnaire. Losses in calf mCSA were significantly reduced in FW (Ctrl: 25.6% F 2.5% Pam: 25.6% F 3.7%, FW: 17.3% F 2.7%), but not in the forearm mCSA (Ctrl: 6.4% F 4.33%, Pam: 7.7% F 4.1%, FW: 7.6% F 3.3%). Both diaphyseal and epiphyseal BMC losses of the tibia were mitigated in Pam and FW as compared to Ctrl, although this was significant only at the diaphysis. Inter-individual variability was significantly greater for changes in BMC than in mCSA, and correlation of BMC losses was poor among different locations of the tibia. A significant positive correlation was found between change in tibia epiphyseal BMC and serum cortisol levels. These findings suggest that both countermeasures are only partly effective to preserve BMC (FW and Pam) and mCSA (FW) of the lower leg during bed rest. The partial efficacy of flywheel exercise as well as the bones’ response to unloading per se underlines the importance of mechanical stimuli. The huge variability of BMC changes, however, suggests that other factors affect changes in whole-bone strength following acute mechanical disuse.
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| 10. |
- Rudnik, Jana, et al.
(author)
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Differential expression of nitric oxide synthases (NOS 1-3) in human skeletal muscle following exercise countermeasure during 12 weeks of bed rest.
- 2004
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In: The F A S E B Journal. - 0892-6638. ; 18:11, s. 1228-1230
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Journal article (peer-reviewed)abstract
- Nitric oxide (NO) generated from NO synthases mediates normal skeletal muscle functions. Biosynthesis of NO apparently is linked to muscle activity, but the distribution and expression of the three major NO synthase 1-3 isoforms under conditions of extended muscle disuse and exercise are still unclear. Our aim was to elucidate whether protein levels and the cellular or subcellular localization patterns of NO synthases underwent significant changes in a mixed fast/slow and slow type skeletal muscle after prolonged disuse in a long-term bed rest study, a useful experimental paradigm of simulated microgravity in ground-based space research. We examined whether resistance exercise performed regularly as a countermeasure to progressive atrophy within 12 wk of strict bed rest would support expression of one or more isoforms of NOS, thereby maintaining normal skeletal muscle functions during immobilization in clinical settings or in human spaceflight.
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