| 1. |
- von Walden, Ferdinand, et al.
(författare)
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Acute endurance exercise stimulates circulating levels of mitochondrial derived peptides in humans
- 2021
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Ingår i: Journal of applied physiology. - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 131:3, s. 1035-1042
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Tidskriftsartikel (refereegranskat)abstract
- Mitochondrial derived peptides (MDPs) humanin (HN) and mitochondrial open reading frame of the 12S rRNA-c (MOTS-c) are involved in cell survival, suppression of apoptosis and metabolism. Circulating levels of MDPs are altered in chronic diseases such as diabetes type 2 and chronic kidney disease. Whether acute resistance (RE) or endurance (EE) exercise modulates circulating levels of HN and MOTS-c in humans is unknown. Following familiarization, subjects were randomized to EE (n=10, 45 min cycling at 70% of estimated VO2max), RE (n=10, 4 sets x 7RM, leg press and knee extension), or control (CON, n=10). Skeletal muscle biopsies and blood samples were collected before and at 30 minutes and 3 hours following exercise. Plasma concentration of HN and MOTS-c, skeletal muscle MOTS-c as well as gene expression of exercise related genes were analyzed. Acute EE and RE promoted changes in skeletal muscle gene expression typically seen in response to each exercise modality (c-Myc, 45S pre-rRNA, PGC-1α-total and PGC-1α-ex1b). At rest, circulating levels of HN were positively correlated to MOTS-c levels and age. Plasma levels of MDPs were not correlated to fitness outcomes (VO2max, leg strength or muscle mitochondrial (mt) DNA copy number). Circulating levels of HN were significantly elevated by acute EE but not RE. MOTS-C levels showed a trend to increase after EE. These results indicate that plasma MDP levels are not related to fitness status but that acute EE increases circulating levels of MDPs, in particular HN.
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| 2. |
- Alkner, Björn A, et al.
(författare)
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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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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 93:3, s. 294-305
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Tidskriftsartikel (refereegranskat)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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| 3. |
- Alkner, Björn, 1968-, et al.
(författare)
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Effect of postoperative pneumatic compression after volar plate fixation of distal radial fractures: a randomized controlled trial
- 2018
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Ingår i: Journal of Hand Surgery, European Volume. - : SAGE PUBLICATIONS LTD. - 1753-1934 .- 2043-6289. ; 43:8, s. 825-831
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the difference between postoperative rehabilitation with or without adjunctive intermittent pneumatic compression therapy following distal radial fracture treated with volar plating. A total of 115 patients were randomized to a control or to an experimental group. After 4 weeks of immobilization the experimental group received intermittent pneumatic compression therapy in addition to conventional postoperative rehabilitation. Primary outcome up to 1 year postoperatively was assessed using the Canadian Occupational Performance Measure. No significant differences between groups were found. There were no clinically relevant differences regarding the secondary outcome measures swelling, strength, pain and flexibility. We conclude that postoperative intermittent pneumatic compression treatment had no major benefits. The results of the present study do not support general use of intermittent pneumatic compression initiated 4 weeks following volar plating surgery for distal radial fracture. Level of evidence: I
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| 4. |
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| 5. |
- Alkner, Björn
(författare)
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Effects of unloading and resistance exercise on skeletal muscle function, size and composition in man
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Exposure to microgravity, i.e., spaceflight, causes muscle unloading leading to muscle atrophy and dysfunction. Thus, there is a need for effective countermeasures to combat these effects. The present thesis aimed to study function, size and composition of anti-gravity muscles following long-duration bed rest, a valid spaceflight analogue. A further and even more important aim was to study the effects of concurrent resistance exercise using a gravityindependent device. Prior to this, the exercise paradigm was validated during space station-like conditions. Four healthy men trained 2-3 times weekly during 110 days of confinement in a ground-based chamber, severely restricting locomotor activity. Training performance progressed over time and maximal voluntary contraction (MVC) was either increased or maintained after confinement. Since the device showed feasibility and potential as a countermeasure against muscle function deterioration, it was subsequently employed during strict unloading. Nine healthy men performed 90 days of bed rest (BR), while another group of eight men in addition carried out resistance exercise for the knee extensors and plantar flexors every third day (BRE). Different indices of muscle function were obtained together with surface electromyographic (EMG) amplitude before and after the intervention. Muscle volume was assessed by means of magnetic resonance imaging (MRI) prior to and on day 29 and 89 during bed rest. Moreover, muscle biopsies were obtained from min. vastus lateralis (VL; all subjects) and soleus (n=3 from each group) before and on day 84 during bed rest, for subsequent analyses of single fibre myosin heavy chain (MHC) content. In BR, muscle volume of the knee extensors decreased (p<0.05) by 10 and 18% on day 29 and 89, respectively. The corresponding decreases for the plantar flexors were 16 and 29%, respectively. In BRE, knee extensor atrophy was prevented (p>0.05), while the more pronounced plantar flexor atrophy was attenuated (-8 and -15%). Maximal torque, force and power, measured during different types of actions, decreased by 31-60% in BR. In BRE, MVC was maintained for the knee extensors but not for the plantar flexors. Training-specific force and power were unaltered for both muscles, while maximal torque measured in actions different from the training task, decreased. EMG amplitude decreased during maximal and increased during submaximal actions in BR, but not in BRE. BR, but not BRE, showed increased fatigability and decreased rate of force development (RFD). In BR, there was an increase in hybrid fibres and a shift towards faster phenotypes in both VL and soleus. In BRE, this effect was attenuated in VL and offset in soleus. The phenotype shift was not manifested in altered force-velocity characteristics. The greater atrophy of the plantar flexors compared to the knee extensors in response to unloading, may be explained by the greater content of slow fibres and the more frequent use of this particular muscle group in daily life. Further, muscle volume and single fibre data suggest that slow fibres are less responsive to the training protocol. The present findings also provide evidence that neural mechanisms, in addition to changes in muscle size, contribute to muscle function alterations induced by bed rest with or without resistance exercise, while phenotype shift may play a more modest role. Hence, it is clear that designing countermeasures for inflight use extends beyond preserving muscle size only. Though the present work was spurred by questions addressed through the human spaceflight program, the results do have important clinical implications for e.g., aging populations or patients undergoing atrophy due to disease or injury.
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| 6. |
- Alkner, Björn, et al.
(författare)
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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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Ingår i: Acta Physioloogica Scandinavica. - 0001-6772. ; 181:3, s. 345-357
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Tidskriftsartikel (refereegranskat)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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| 7. |
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| 8. |
- Alkner, Björn, 1968-, et al.
(författare)
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Muscle Activation During Gravity-Independent Resistance Exercise Compared to Common Exercises
- 2019
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Ingår i: Aerospace Medicine and Human Performance. - : AEROSPACE MEDICAL ASSOC. - 2375-6314 .- 2375-6322. ; 90:6, s. 506-512
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Tidskriftsartikel (refereegranskat)abstract
- INTRODUCTION: The aim was to study quadriceps muscle activation during resistance exercise using a flywheel device, developed as a gravity-independent resistance exercise device to be used during spaceflight, compared with traditional strength training exercises. METHODS: Eight healthy men experienced in resistance exercise performed the following exercises in random order: flywheel leg press (FW), knee extension isokinetic dynamometry (ID), barbell front squat (FS), weight stack leg press (LP), and weight stack knee extension (KE). They accomplished eight repetitions of coupled concentric and eccentric actions with simultaneous recordings of surface electromyography (EMG) from the three superficial quadriceps muscles and knee angles using electrogoniometry. Maximal voluntary contraction (MVC) in knee extension was performed before and after these measurements. RESULTS: EMG averaged across muscles and angles and normalized to MVC was 99/76% in FW, 48/41% FS, 65/47% LP, 81/52% KE, and 93/84% ID in concentric/eccentric phases, respectively. FW and ID showed higher mean EMG activity than LP and FS concentrically and higher than all other exercises eccentrically. No difference in activity between FW and ID was found. Pre- and post-MVC torque was comparable. DISCUSSION: Quadriceps muscle activation was superior in FW and ID exercises compared to the other exercises. The difference was most pronounced in the eccentric phase, but even concentric activation was lower in traditional closed chain exercises. This data supports that FW is an effective training tool and should be considered when designing strength training programs for spaceflights and on Earth.
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| 9. |
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| 10. |
- Beato, Marco, et al.
(författare)
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Current Guidelines for the Implementation of Flywheel Resistance Training Technology in Sports: A Consensus Statement
- 2024
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Ingår i: Sports Medicine. - : ADIS INT LTD. - 0112-1642 .- 1179-2035.
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Forskningsöversikt (refereegranskat)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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