An investigation of the influence of creep on low frequency fatigue of 1Kh18N9T steel at high temperatures

1970 ◽  
Vol 2 (4) ◽  
pp. 335-339 ◽  
Author(s):  
E. A. Antipov
Keyword(s):  
High Temperatures ◽  
Low Frequency ◽  
1Kh18n9t Steel ◽  
Low Frequency Fatigue

Effects of activation frequency and force on low-frequency fatigue in human skeletal muscle

1999 ◽  
Vol 86 (4) ◽  
pp. 1337-1346 ◽  
Author(s):  
Stuart A. Binder-Macleod ◽  
David W. Russ
Keyword(s):  
Healthy Subjects ◽  
Human Skeletal Muscle ◽  
Low Frequency ◽  
Variable Frequency ◽  
Activation Pattern ◽  
Constant Frequency ◽  
Mean Frequency ◽  
Before And After ◽  
Low Frequency Fatigue ◽  
Force Time

No comparison of the amount of low-frequency fatigue (LFF) produced by different activation frequencies exists, although frequencies ranging from 10 to 100 Hz have been used to induce LFF. The quadriceps femoris of 11 healthy subjects were tested in 5 separate sessions. In each session, the force-generating ability of the muscle was tested before and after fatigue and at 2, ∼13, and ∼38 min of recovery. Brief (6-pulse), constant-frequency trains of 9.1, 14.3, 33.3, and 100 Hz and a 6-pulse, variable-frequency train with a mean frequency of 14.3 Hz were delivered at 1 train/s to induce fatigue. Immediately postfatigue, there was a significant effect of fatiguing protocol frequency. Muscles exhibited greater LFF after stimulation with the 9.1-, 14.3-, and variable-frequency trains. These three trains also produced the greatest mean force-time integrals during the fatigue test. At 2, ∼13, and ∼38 min of recovery, however, the LFF produced was independent of the fatiguing protocol frequency. The findings are consistent with theories suggesting two independent mechanisms behind LFF and may help identify the optimal activation pattern when functional electrical stimulation is used.

scholarly journals Low-frequency fatigue at maximal and submaximal muscle contractions

2009 ◽  
Vol 42 (4) ◽  
pp. 380-385 ◽  
Author(s):  
R.R. Baptista ◽  
E.M. Scheeren ◽  
B.R. Macintosh ◽  
M.A. Vaz
Keyword(s):  
Low Frequency ◽  
Muscle Contractions ◽  
Low Frequency Fatigue

Central and peripheral contributions to neuromuscular fatigue induced by a 24-h treadmill run

2010 ◽  
Vol 108 (5) ◽  
pp. 1224-1233 ◽  
Author(s):  
Vincent Martin ◽  
Hugo Kerhervé ◽  
Laurent A. Messonnier ◽  
Jean-Claude Banfi ◽  
André Geyssant ◽  
...  
Keyword(s):  
Compound Muscle Action Potential ◽  
Vastus Lateralis ◽  
Low Frequency ◽  
Force Production ◽  
Neuromuscular Fatigue ◽  
Voluntary Activation ◽  
Knee Extensors ◽  
Function Evaluation ◽  
Central Component ◽  
Low Frequency Fatigue

This experiment investigated the fatigue induced by a 24-h running exercise (24TR) and particularly aimed at testing the hypothesis that the central component would be the main mechanism responsible for neuromuscular fatigue. Neuromuscular function evaluation was performed before, every 4 h during, and at the end of the 24TR on 12 experienced ultramarathon runners. It consisted of a determination of the maximal voluntary contractions (MVC) of the knee extensors (KE) and plantar flexors (PF), the maximal voluntary activation (%VA) of the KE and PF, and the maximal compound muscle action potential amplitude (Mmax) on the soleus and vastus lateralis. Tetanic stimulations also were delivered to evaluate the presence of low-frequency fatigue and the KE maximal muscle force production ability. Strength loss occurred throughout the exercise, with large changes observed after 24TR in MVC for both the KE and PF muscles (−40.9 ± 17.0 and −30.3 ± 12.5%, respectively; P < 0.001) together with marked reductions of %VA (−33.0 ± 21.8 and −14.8 ± 18.9%, respectively; P < 0.001). A reduction of Mmax amplitude was observed only on soleus, and no low-frequency fatigue was observed for any muscle group. Finally, KE maximal force production ability was reduced to a moderate extent at the end of the 24TR (−10.2%; P < 0.001), but these alterations were highly variable ( ± 15.7%). These results suggest that central factors are mainly responsible for the large maximal muscle torque reduction after ultraendurance running, especially on the KE muscles. Neural drive reduction may have contributed to the relative preservation of peripheral function and also affected the evolution of the running speed during the 24TR.

scholarly journals Low-Frequency Fatigue at Different Muscle Length Following Intermittent Eccentric Drop Jumps in 12—14 Year-Old Boys

2018 ◽  
Vol 3 (57) ◽  
Author(s):  
Vytautas Streckis ◽  
Giedrius Gorianovas ◽  
Birutė Miseckaitė ◽  
Valerija Streckienė ◽  
Ronaldas Endrijaitis ◽  
...  
Keyword(s):  
Electrical Stimulation ◽  
Eccentric Exercise ◽  
Mechanical Damage ◽  
Low Frequency ◽  
Muscle Length ◽  
Contraction Force ◽  
Low Frequencies ◽  
Drop Jumps ◽  
Low Frequency Fatigue ◽  
Initial Force

Low frequency fatigue (LFF) in 12—14 year-old adolescent boys (n = 10) doing 75 eccentric jumps performed every20 s from a platform 80 cm high was investigated.Thus the aim of this study was to find out if LFF manifests itself in the muscles of boys aged 12—14 years doing 75 dropjumps performed every 20 s at angles of 90˚ and 135˚ from a platform 80 cm high. The results of the research have shownthat doing 75 eccentric jumps performed every 20 s calls forth LFF in the muscles of boys that is particularly strong anddisappears more slowly at a shorter length of the muscle exercised. Thus, the hypothesis as to the sarcomeric origin ofLFF in the muscles of boys and men has been confirmed. Besides, the muscles of men of mature age are more resistantto LFF than those of boys. This fact, as well as a more acute pain brought about in the muscles of boys, indicates thatthe muscles of boys are less resistant to mechanical damage than those of men of mature age.It is maintained that as a result of the eccentric exercise performed, some portion of the weak sarcomeres gets tornand then the strong sarcomeres, i.e. the ones that develop contraction force have to work at a shorter muscle length.When muscle contraction length is short the sensitiveness of miofibrillas to Ca 2+  decreases. It is rather unexpectedthough that 24 h after the end of the exercise the force developed by electrostimulation at low frequencies (20 Hz) issmaller (p < 0.05), as compared to the initial force registered at a shorter muscle length. Since after the exercise therewas also a decrease in the force developed at a shorter muscle length in particular, the sarcomeres are believed tohave been damaged during eccentric exercise.Keywords: electrical stimulation, force, age, muscle damage, stretch-shortening exercise.

Role of intracellular calcium and metabolites in low-frequency fatigue of mouse skeletal muscle

1997 ◽  
Vol 272 (2) ◽  
pp. C550-C559 ◽  
Author(s):  
E. R. Chin ◽  
C. D. Balnave ◽  
D. G. Allen
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Low Frequency ◽  
Single Muscle ◽  
Low Frequencies ◽  
Time Integral ◽  
Metabolic Component ◽  
Dependent Component ◽  
Low Frequency Fatigue

We have examined the extent to which prolonged reductions in low-frequency force (i.e., low-frequency fatigue) result from increases in intracellular free Ca2+ concentration ([Ca2+]i) and alterations in muscle metabolites. Force and [Ca2+]i were measured in mammalian single muscle fibers in response to short, intermediate, and long series of tetani that elevated the [Ca2+]i-time integral to 5, 17, and 29 microM x s, respectively. Only the intermediate and long series resulted in prolonged (>60 x min) reductions in Ca2+ release and low-frequency fatigue. When fibers recovered from the long series of tetani without glucose, Ca2+ release was reduced to a greater extent and force was reduced at high and low frequencies. These findings indicate that the decrease in sarcoplasmic reticulum Ca2+ release associated with fatigue has at least two components: 1) a metabolic component, which, in the presence of glucose, recovers within 1 h, and 2) a component dependent on the elevation of the [Ca2+]i-time integral, which recovers more slowly. It is this Ca2+-dependent component that is primarily responsible for low-frequency fatigue.

scholarly journals Low-Frequency Fatigue as an Indicator of Eccentric Exercise-Induced Muscle Injury: The Role of Vitamin E

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Antonios Kyparos ◽  
Michalis G. Nikolaidis ◽  
Konstantina Dipla ◽  
Andreas Zafeiridis ◽  
Vassilis Paschalis ◽  
...  
Keyword(s):  
Vitamin E ◽  
Eccentric Exercise ◽  
Muscle Injury ◽  
Low Frequency ◽  
Low Frequency Fatigue ◽  
Exercise Induced

Elasto-Viscoplastic Dispersive Waves in Silicon Wafers

2007 ◽  
Author(s):  
Li Liu ◽  
C. Steve Suh
Keyword(s):  
Stress Wave ◽  
High Temperatures ◽  
Nonlinear Function ◽  
Low Frequency ◽  
Propagation Model ◽  
Constitutive Law ◽  
Stress Wave Propagation ◽  
Thickness Variation ◽  
Low Frequencies ◽  
Induced Stress

This paper provides the required knowledge base for establishing Laser Induced Stress Wave Thermometry (LISWT) as a viable alternative to current infrared technologies for temperature measurement up to 1000°C with ±1°C resolution. A stress wave propagation model having a complex, temperature-dependent elasto-viscoplastic constitutive law is developed. Investigated results show that wave group velocity is a nonlinear function of temperature. Nonlinearity becomes more prominent at high temperatures and low frequencies. As such, for LISWT to achieve better thermal resolution at high temperatures, low frequency components of the induced stress wave should be exploited. The results also show that the influence of temperature on attenuation is relatively small. It is not recommended to use attenuation for resolving temperature variation as small as several degrees Celsius. In addition to temperature, geometry also is found to have an impact on wave dispersion and attenuation. The influence of thickness on wave velocity is significant, thus suggesting that for LISWT to achieve high temperature resolution, wafer thickness must be accurately calibrated in order to eliminate all possible errors introduced by thickness variation.

Is Weaning Failure Caused by Low-Frequency Fatigue of the Diaphragm?

2003 ◽  
Vol 167 (2) ◽  
pp. 120-127 ◽  
Author(s):  
Franco Laghi ◽  
Steven E. Cattapan ◽  
Amal Jubran ◽  
Sairam Parthasarathy ◽  
Paul Warshawsky ◽  
...  
Keyword(s):  
Low Frequency ◽  
Weaning Failure ◽  
Low Frequency Fatigue
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