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  • Isokinetic training  (2)
  • Median frequency  (2)
  • Key words Chronic low back pain  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Influence of age and duration of symptoms on fibre type distribution and size of the back muscles in chronic low back pain patients (2000)
    Springer
    European spine journal 9 (2000), S. 273-281 
    Details
    ISSN: 1432-0932
    Keywords: Key words Chronic low back pain ; Erector spinae muscle ; MRI ; Muscle biopsy ; Fibre type ; distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Many studies have documented an association between chronic low back pain (LBP) and deficits in back muscle strength and endurance. The sub-optimal performance is believed to be the result of alterations in the size and structure of the muscle, although the long-standing issue of whether the observed changes precede or are a consequence of the pain remains unresolved. If consequent to the problem, and predominantly related to disuse of the muscles, then it may be expected that a relationship between muscle structure and symptom duration would exist. Lumbar paraspinal muscle samples were obtained from 59 chronic LBP patients using the percutaneous biopsy technique. The samples were subject to routine histochemical analysis for the examination of muscle fibre type characteristics and cytochemical architectural changes. In 55 of the patients, the gross cross-sectional areas of magnetic resonance images of the trunk muscles were also measured. Multivariate analysis showed that symptom duration was the strongest predictor of the individual proportions of the fast-fatigable type IIX fibres; with age and gender included in the model, nearly 30% of the variance in fibre type distribution could be accounted for. Duration of pain had no influence on fibre size. Gross muscle cross-sectional area correlated directly with lean body mass and inversely with age, but showed no relationship with symptom duration. Pathological changes in the internal fibre structure were more frequently encountered in older patients, and were independent of symptom duration. The results suggest that, over the long term, fibre type transformations rather than alterations in fibre size are the predominant changes to be found in the muscles of chronic LBP patients. The direction of change supports the results of many previous studies that have demonstrated corresponding differences in the fatigability of the muscles. There is a strong case for the early implementation of active measures to attempt to offset the development of these changes in back pain patients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005860000189
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Relationship between myoelectric and mechanical manifestations of fatigue in the quadriceps femoris muscle group (1996)
    Springer
    European journal of applied physiology 74 (1996), S. 411-419 
    Details
    ISSN: 1439-6327
    Keywords: Electromyography ; Power spectrum ; Median frequency ; Muscle force ; Muscle fatigue
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Fatigue is commonly defined as “the failure to maintain the required force”. As such, it may be argued that the use of electromyographic (EMG) power spectral statistics to monitor muscle fatigue is inappropriate, because, during the maintenance of a submaximal force of contraction, EMG changes are readily observable in the absence of any decline in the muscle's mechanical output. However, it is possible that the EMG changes reflect the changing metabolic status of the muscle and hence its inability to generate its normal maximal force. The present study sought to examine whether the decline in EMG median frequency, which occurs during the maintenance of a submaximal force, is correlated with a reduction in the muscle's maximum force-generating capacity. The maximum voluntary contraction (MVC) of the knee extensors in ten young, healthy subjects was determined. On five separate occasions, randomly assigned forces of 20, 30, 40, 50 and 60% MVC were held to the limit of endurance. At intervals throughout the sustained contractions, subjects were required to rapidly generate an MVC for 1–2 s, then return to the fixed submaxial target force. Surface EMG signals were recorded throughout the contractions from the rectus lemons and vastus lateralis muscles, from which the power spectrum median frequency was calculated. Regression analysis revealed highly significant relationships between the rate of decline in MF and the rate of decline in MVC, and between each of these parameters and endurance time to fatigue (P = 0.0001, in each case). It is concluded that the decline in MF can be used to monitor fatigue, where fatigue is defined as the inability to generate the maximum force that can be produced by the muscle in its fresh state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02337721
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of isokinetic training of the knee extensors on high-intensity exercise performance and skeletal muscle buffering (1994)
    Springer
    European journal of applied physiology 68 (1994), S. 356-361 
    Details
    ISSN: 1439-6327
    Keywords: Isokinetic training ; Knee extensors ; High-intensity exercise ; Muscle carnosine ; Muscle buffering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Twenty-three subjects isokinetically trained the right and left quadriceps femoris, three times per week for 16 weeks; one group (n=13) trained at an angular velocity of 4.19 rad · s−1 and a second group (n=10), at 1.05 rad · s−1. A control group (n=10) performed no training. Isometric endurance time at 60% quadriceps maximum voluntary contraction (MVC), mean power output and work done (W) during all-out cycling, and the muscle buffer value (B) and carnosine concentration of biopsy samples from the vastus lateralis, were all assessed before and after training. The two training groups did not differ significantly from each other in their training response to any of these variables (P 〈 0.05). No significant difference in either 60% MVC endurance time or impulse [(endurance time × force) at 60% MVC] was observed for any group after the 16 week period (P 〉 0.05). However, the post-training increase (9%) in W during high-intensity cycling was greater in the training group than in the control group (P=0.04). NeitherB nor carnosine concentration showed any significant change following training (P=0.56 andP=0.37, respectively). It is concluded that 16 weeks of isokinetic training of the knee extensors enables subjects to do more work during high-intensity cycling. Although the precise adaptations responsible for the improved performance have yet to be identified, they are unlikely to include an increase inB.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00571457
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of isokinetic training of the knee extensors on isometric strength and peak power output during cycling (1992)
    Springer
    European journal of applied physiology 65 (1992), S. 370-375 
    Details
    ISSN: 1439-6327
    Keywords: Isokinetic training ; Strength ; Maximum voluntary contraction ; Knee extensors ; Sprint cycle power output
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Isokinetic training of right and left quadriceps femoris was undertaken three times per week for 16 weeks. One group of subjects (n=13) trained at an angular velocity of 4.19 rad·s−1 and a second group (n=10) at 1.05 rad·s−1. A control group (n=10) performed no training. Maximal voluntary contraction (MVC) of the quadriceps, and peak pedal velocity (νp,peak) and peak power output (W peak) during all-out cycling (against loads equivalent to 9, 10, 11, 12, 13 and 14% MVC) were assessed before and after training. The two training groups did not differ significantly from each other in their training response to any of the performance variables (P〉0.05). No significant difference in MVC was observed for any group after the 16-week period (P=0.167). The post-training increases in averageW peak (7%) and νp,peak (6%) during the cycle tests were each significantly different from the control group response (P=0.018 andP=0.008, respectively). It is concluded that 16 weeks of isokinetic strength training of the knee extensors is able to significantly improve νp,peak andW peak during sprint cycling, an activity which demands considerable involvement of the trained muscle group but with its own distinct pattern of coordination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00868143
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    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Relationship between myoelectric and mechanical manifestations of fatigue in the quadriceps femoris muscle group (1996)
    Springer
    European journal of applied physiology 74 (1996), S. 411-419 
    Details
    ISSN: 1439-6327
    Keywords: Key words Electromyography ; Power spectrum ; Median frequency ; Muscle force ; Muscle fatigue
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Fatigue is commonly defined as “the failure to maintain the required force”. As such, it may be argued that the use of electromyographic (EMG) power spectral statistics to monitor muscle fatigue is inappropriate, because, during the maintenance of a submaximal force of contraction, EMG changes are readily observable in the absence of any decline in the muscle’s mechanical output. However, it is possible that the EMG changes reflect the changing metabolic status of the muscle and hence its inability to generate its normal maximal force. The present study sought to examine whether the decline in EMG median frequency, which occurs during the maintenance of a submaximal force, is correlated with a reduction in the muscle’s maximum force-generating capacity. The maximum voluntary contraction (MVC) of the knee extensors in ten young, healthy subjects was determined. On five separate occasions, randomly assigned forces of 20, 30, 40,  50 and 60% MVC were held to the limit of endurance. At intervals throughout the sustained contractions, subjects were required to rapidly generate an MVC for 1–2 s, then return to the fixed submaxial target force. Surface EMG signals were recorded throughout the contractions from the rectus femoris and vastus lateralis muscles, from which the power spectrum median frequency was calculated. Regression analysis revealed highly significant relationships between the rate of decline in MF and the rate of decline in MVC, and between each of these parameters and endurance time to fatigue (P=0.0001, in each case). It is concluded that the decline in MF can be used to monitor fatigue, where fatigue is defined as the inability to generate the maximum force that can be produced by the muscle in its fresh state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004210050094
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
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