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- 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. |
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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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| 6. |
- 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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| 7. |
- Trappe, Scott, et al.
(author)
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Human single muscle fibre function with 84 day bed-rest and resistance exercise.
- 2004
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In: Journal of physiology. - : Wiley. - 0022-3751. ; 557, s. 501-513
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Journal article (peer-reviewed)abstract
- Muscle biopsies were obtained from the vastus lateralis before and after 84 days of bed-rest fromsix control (BR) and six resistance-exercised (BRE) men to examine slow- and fast-twitch muscle fibre contractile function. BR did not exercise during bed-rest and had a 17 and 40% decrease inwholemuscle size and function, respectively. TheBREgroup performedfour sets of seven maximal concentric and eccentric supine squats 2–3 days perweek (every third day) that maintained whole muscle strength and size. Slow (MHC I) and fast (MHC IIa) muscle fibres were studied at 15◦C for diameter, peak force (Po), contractile velocity (Vo) and force–power parameters. SDS-PAGE was performed on each single fibre after the functional experiments to determine MHC isoform composition. MHCI and IIa BR fibres were, respectively, 15 and 8% smaller, 46 and 25% weaker (Po), 21 and 6% slower (Vo), and 54 and 24% less powerful after bed-rest (P<0.05). BR MHCI and IIa Po and power normalized to cell size were lower (P<0.05). BRE MHCI fibres showed no change in size or Vo after bed-rest; however, Po was 19%lower (P<0.05), resulting in 20 and30%declines (P<0.05) in normalizedPo and power, respectively. BREMHCIIa fibres showed no change in size, Po and power after bed-rest, while Vo waselevated13%(P<0.05).BREMHCIIanormalizedPo andpowerwere10and15%lower (P<0.05), respectively.MHCisoformcomposition shifted away fromMHCI fibres, resulting in an increase (P<0.05) inMHCI/IIa (BR and BRE) andMHCIIa/IIx (BR only) fibres. These data show that the contractile function of the MHCI fibres was more affected by bed-rest and less influenced by the resistance exercise protocol than the MHCIIa fibres. Considering the large differences inpower ofhumanMHCIandIIamusclefibres (5- to6-fold), the maintenance of wholemuscle function with the resistance exercise programme is probably explained by (1) the maintenance of MHCIIa power and (2) the shift from slow to fast (MHC I→MHCI/IIa) in
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