more information
Search within Results:

Select All    Deselect All
 |   | 
Details
   print
  Records Links
Author (up) Atherton, P.J.; Babraj, J.; Smith, K.; Singh, J.; Rennie, M.J.; Wackerhage, H. file  url
openurl 
  Title Selective activation of AMPK-PGC-1alpha or PKB-TSC2-mTOR signaling can explain specific adaptive responses to endurance or resistance training-like electrical muscle stimulation Type Journal Article
  Year 2005 Publication FASEB Journal : Official Publication of the Federation of American Societies for Experimental Biology Abbreviated Journal Faseb J  
  Volume 19 Issue 7 Pages 786-788  
  Keywords Adaptation, Physiological; Adenylate Kinase/*metabolism; Animals; Electric Stimulation; Enzyme Activation; Male; Mitogen-Activated Protein Kinases/metabolism; Muscle Contraction; Muscle Proteins/biosynthesis; Muscle, Skeletal/*physiology; Myofibrils/metabolism; Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; Phosphorylation; Physical Conditioning, Animal; Physical Endurance/physiology; Physical Exertion; Protein Kinases/*metabolism; Proto-Oncogene Proteins c-akt/*metabolism; RNA-Binding Proteins/*metabolism; Rats; Rats, Wistar; Sarcoplasmic Reticulum/metabolism; Signal Transduction; TOR Serine-Threonine Kinases; Transcription Factors/*metabolism; Tumor Suppressor Proteins/*metabolism  
  Abstract Endurance training induces a partial fast-to-slow muscle phenotype transformation and mitochondrial biogenesis but no growth. In contrast, resistance training mainly stimulates muscle protein synthesis resulting in hypertrophy. The aim of this study was to identify signaling events that may mediate the specific adaptations to these types of exercise. Isolated rat muscles were electrically stimulated with either high frequency (HFS; 6x10 repetitions of 3 s-bursts at 100 Hz to mimic resistance training) or low frequency (LFS; 3 h at 10 Hz to mimic endurance training). HFS significantly increased myofibrillar and sarcoplasmic protein synthesis 3 h after stimulation 5.3- and 2.7-fold, respectively. LFS had no significant effect on protein synthesis 3 h after stimulation but increased UCP3 mRNA 11.7-fold, whereas HFS had no significant effect on UCP3 mRNA. Only LFS increased AMPK phosphorylation significantly at Thr172 by approximately 2-fold and increased PGC-1alpha protein to 1.3 times of control. LFS had no effect on PKB phosphorylation but reduced TSC2 phosphorylation at Thr1462 and deactivated translational regulators. In contrast, HFS acutely increased phosphorylation of PKB at Ser473 5.3-fold and the phosphorylation of TSC2, mTOR, GSK-3beta at PKB-sensitive sites. HFS also caused a prolonged activation of the translational regulators p70 S6k, 4E-BP1, eIF-2B, and eEF2. These data suggest that a specific signaling response to LFS is a specific activation of the AMPK-PGC-1alpha signaling pathway which may explain some endurance training adaptations. HFS selectively activates the PKB-TSC2-mTOR cascade causing a prolonged activation of translational regulators, which is consistent with increased protein synthesis and muscle growth. We term this behavior the “AMPK-PKB switch.” We hypothesize that the AMPK-PKB switch is a mechanism that partially mediates specific adaptations to endurance and resistance training, respectively.  
  Call Number Serial 2075  
Permanent link to this record
 

 
Author (up) Farina, D.; Jiang, N.; Rehbaum, H.; Holobar, A.; Graimann, B.; Dietl, H.; Aszmann, O.C. file  url
openurl 
  Title The extraction of neural information from the surface EMG for the control of upper-limb prostheses: emerging avenues and challenges Type Journal Article
  Year 2014 Publication IEEE Transactions on Neural Systems and Rehabilitation Engineering : a Publication of the IEEE Engineering in Medicine and Biology Society Abbreviated Journal IEEE Trans Neural Syst Rehabil Eng  
  Volume 22 Issue 4 Pages 797-809  
  Keywords Action Potentials/*physiology; Arm; Artificial Intelligence/trends; Artificial Limbs/*trends; Electromyography/*trends; Feedback, Physiological/physiology; Humans; Movement/*physiology; Muscle Contraction/*physiology; Muscle, Skeletal/*physiology; Pattern Recognition, Automated/*trends  
  Abstract Despite not recording directly from neural cells, the surface electromyogram (EMG) signal contains information on the neural drive to muscles, i.e., the spike trains of motor neurons. Using this property, myoelectric control consists of the recording of EMG signals for extracting control signals to command external devices, such as hand prostheses. In commercial control systems, the intensity of muscle activity is extracted from the EMG and used for single degrees of freedom activation (direct control). Over the past 60 years, academic research has progressed to more sophisticated approaches but, surprisingly, none of these academic achievements has been implemented in commercial systems so far. We provide an overview of both commercial and academic myoelectric control systems and we analyze their performance with respect to the characteristics of the ideal myocontroller. Classic and relatively novel academic methods are described, including techniques for simultaneous and proportional control of multiple degrees of freedom and the use of individual motor neuron spike trains for direct control. The conclusion is that the gap between industry and academia is due to the relatively small functional improvement in daily situations that academic systems offer, despite the promising laboratory results, at the expense of a substantial reduction in robustness. None of the systems so far proposed in the literature fulfills all the important criteria needed for widespread acceptance by the patients, i.e. intuitive, closed-loop, adaptive, and robust real-time ( 200 ms delay) control, minimal number of recording electrodes with low sensitivity to repositioning, minimal training, limited complexity and low consumption. Nonetheless, in recent years, important efforts have been invested in matching these criteria, with relevant steps forwards.  
  Call Number Serial 2093  
Permanent link to this record
 

 
Author (up) Wagner, P.D. file  url
openurl 
  Title New ideas on limitations to VO2max Type Journal Article
  Year 2000 Publication Exercise and Sport Sciences Reviews Abbreviated Journal Exerc Sport Sci Rev  
  Volume 28 Issue 1 Pages 10-14  
  Keywords Altitude; *Cardiac Output; Exercise/*physiology; Humans; Muscle, Skeletal/*physiology; *Oxygen Consumption; Physical Endurance/physiology; *Pulmonary Diffusing Capacity  
  Abstract VO2max indicates maximal oxidative metabolic capacity (unfit subjects) or maximal O2 supply (athletes). The latter reflects integration of all transport steps from air to cytochromes. Every step contributes something; the importance of each contribution varies with conditions. Cardiac output seems most important at sea level; at higher altitudes, lung/muscle diffusion are more critical.  
  Call Number Serial 446  
Permanent link to this record
Select All    Deselect All
 |   | 
Details
   print

Save Citations: