| 1. |
- Pozzo, Marco, et al.
(författare)
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Muscle-fiber conduction velocity during concentric and eccentric actions on a flywheel exercise device
- 2006
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Ingår i: Muscle and Nerve. - : Wiley. - 0148-639X .- 1097-4598. ; 34:2, s. 169-177
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Tidskriftsartikel (refereegranskat)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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| 2. |
- Severinsen, Kaare, et al.
(författare)
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Skeletal muscle fiber characteristics and oxidative capacity in hemiparetic stroke survivors
- 2016
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Ingår i: Muscle and Nerve. - : Wiley. - 0148-639X .- 1097-4598. ; 53:5, s. 748-754
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Skeletal muscle is changed after stroke, but conflicting data exist concerning muscle morphology and oxidative enzyme capacity. Methods: In 36 chronic stroke patients bilateral rectus femoris muscle biopsies were analyzed, and fiber type proportions and cross-sectional areas were determined by ATPase histochemistry. Enzymatic concentrations of citrate synthase (CS) and 3-Hydroxyacyl-coenzymeA-dehydrogenase (HAD) were determined using freeze-dried muscle tissue. Findings were correlated with clinical outcomes. Results: In the paretic muscles the mean fiber area was smaller (P=0.0004), and a lower proportion of type 1 fibers (P=0.0016) and a higher proportion of type 2X fibers (P=0.0002) were observed. The paretic muscle had lower CS (P=0.013) and HAD concentrations (P=0.037). Mean fiber area correlated with muscle strength (r=0.43; P=0.041), and CS concentration correlated with aerobic capacity (r=0.47; P=0.01). Conclusions: In stroke survivors there is a phenotypic shift toward more fatigable muscle fibers with reduced oxidative enzymatic capacity that relates to clinical outcomes. Muscle Nerve53: 748-754, 2016
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| 3. |
- Zinner, Christoph, et al.
(författare)
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Effect of resistance training with vibration and compression on the formation of muscle and bone
- 2017
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Ingår i: Muscle and Nerve. - : Wiley. - 0148-639X .- 1097-4598. ; 56:6, s. 1137-1142
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Tidskriftsartikel (refereegranskat)abstract
- IntroductionIn this study we investigated the effects of resistance training with vibration in combination with leg compression to restrict blood flow on strength, muscle oxygenation, muscle mass, and bone formation. MethodsTwelve participants were tested before and after 12 weeks of resistance training with application of vibration (VIBRA; 1-2mm, 30Hz) to both legs and compression (approximate to 35mm Hg, VIBRA+COMP) to only 1 leg. ResultsVIBRA+COMP and VIBRA improved 1 repetition maximum (1-RM), increased the number of repetitions preceding muscle exhaustion, enhanced cortical bone mass, and lowered the mass and fat fraction in the thigh, with no changes in total muscle mass. The mass of cancellous bone decreased to a similar extent after VIBRA and VIBRA+COMP. DiscussionResistance training with VIBRA+COMP and VIBRA improved 1-RM, increased the number of repetitions preceding muscular exhaustion, and enhanced formation of cortical bone, with no alteration of muscle mass.
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