Role of signal-dependent noise during maintenance of isometric force

Bedrov, Y. A.; Dick, O. E.; Romanov, S. P.

doi:10.1016/j.biosystems.2006.04.011

Cited by 5 publications

(3 citation statements)

References 9 publications

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“…In view of amplitude suppression, the ability to fine-tune force trajectory was less damaged by the fatiguing protocol than the capacity to generate rhythmic force was. Previous studies using static fatigue protocol have shown that fatigue increases in relative force variability [45], [46]. Our finding generalized the concept to rhythmic isometric contraction in terms of reduced R IF/FP in the post-fatigue condition, implying the probability to miss the target increases if the same force pattern is planned during fatigue.…”

Section: Discussionsupporting

confidence: 77%

Fatigue Effect on Low-Frequency Force Fluctuations and Muscular Oscillations during Rhythmic Isometric Contraction

2014

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Continuous force output containing numerous intermittent force pulses is not completely smooth. By characterizing force fluctuation properties and force pulse metrics, this study investigated adaptive changes in trajectory control, both force-generating capacity and force fluctuations, as fatigue progresses. Sixteen healthy subjects (20–24 years old) completed rhythmic isometric gripping with the non-dominant hand to volitional failure. Before and immediately following the fatigue intervention, we measured the gripping force to couple a 0.5 Hz sinusoidal target in the range of 50–100% maximal voluntary contraction. Dynamic force output was off-line decomposed into 1) an ideal force trajectory spectrally identical to the target rate; and 2) a force pulse trace pertaining to force fluctuations and error-correction attempts. The amplitude of ideal force trajectory regarding to force-generating capacity was more suppressed than that of the force pulse trace with increasing fatigue, which also shifted the force pulse trace to lower frequency bands. Multi-scale entropy analysis revealed that the complexity of the force pulse trace at high time scales increased with fatigue, contrary to the decrease in complexity of the force pulse trace at low time scales. Statistical properties of individual force pulses in the spatial and temporal domains varied with muscular fatigue, concurrent with marked suppression of gamma muscular oscillations (40–60 Hz) in the post-fatigue test. In conclusion, this study first reveals that muscular fatigue impairs the amplitude modulation of force pattern generation more than it affects the amplitude responsiveness of fine-tuning a force trajectory. Besides, motor fatigue results disadvantageously in enhancement of motor noises, simplification of short-term force-tuning strategy, and slow responsiveness to force errors, pertaining to dimensional changes in force fluctuations, scaling properties of force pulse, and muscular oscillation.

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Section: Discussionsupporting

confidence: 77%

Fatigue Effect on Low-Frequency Force Fluctuations and Muscular Oscillations during Rhythmic Isometric Contraction

2014

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“…On account of an exertion-dependent increase in force variability [18], [19], precise control of force is far more difficult at a higher force range than at a lower force range. Force stability at a higher force range presumably relies on task-dependent variations in code rating in that motor units are largely recruited [20].…”

Section: Introductionmentioning

confidence: 99%

Trajectory Adjustments Underlying Task-Specific Intermittent Force Behaviors and Muscular Rhythms

et al. 2013

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Force intermittency is one of the major causes of motor variability. Focusing on the dynamics of force intermittency, this study was undertaken to investigate how force trajectory is fine-tuned for static and dynamic force-tracking of a comparable physical load. Twenty-two healthy adults performed two unilateral resistance protocols (static force-tracking at 75% maximal effort and dynamic force-tracking in the range of 50%–100% maximal effort) using the left hand. The electromyographic activity and force profile of the designated hand were monitored. Gripping force was off-line decomposed into a primary movement spectrally identical to the target motion and a force intermittency profile containing numerous force pulses. The results showed that dynamic force-tracking exhibited greater intermittency amplitude and force pulse but a smaller amplitude ratio of primary movement to force intermittency than static force-tracking. Multi-scale entropy analysis revealed that force intermittency during dynamic force-tracking was more complex on a low time scale but more regular on a high time scale than that of static force-tracking. Together with task-dependent force intermittency properties, dynamic force-tracking exhibited a smaller 8–12 Hz muscular oscillation but a more potentiated muscular oscillation at 35–50 Hz than static force-tracking. In conclusion, force intermittency reflects differing trajectory controls for static and dynamic force-tracking. The target goal of dynamic tracking is achieved through trajectory adjustments that are more intricate and more frequent than those of static tracking, pertaining to differing organizations and functioning of muscular oscillations in the alpha and gamma bands.

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“…As a rule, this process is evaluated by analyzing the frequency spectrum of fluctuations emerging during maintenance of isometric effort of human hand [1,4]. The developing disease is attributed to synchronization of the motor units fluctuations, which are normally assumed to be desynchronized [3,6].…”

mentioning

confidence: 99%

Method for Detecting Quantitative Differences in the Parameters of Involuntary Effort Fluctuations in Healthy Volunteers and Patients with Parkinson’s Syndrome

et al. 2008

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The aim of the study was to detect quantitative differences in the parameters of involuntary effort fluctuations in healthy volunteers and patients with Parkinson's syndrome. Using a mathematical model, the process of isometric effort maintenance was separated into rapid (involuntary) and slow (voluntary) constituents. Significant differences were detected for the attenuation coefficient of fluctuations in the involuntary constituent, but not for the frequency.

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Role of signal-dependent noise during maintenance of isometric force

Cited by 5 publications

References 9 publications

Fatigue Effect on Low-Frequency Force Fluctuations and Muscular Oscillations during Rhythmic Isometric Contraction

Fatigue Effect on Low-Frequency Force Fluctuations and Muscular Oscillations during Rhythmic Isometric Contraction

Trajectory Adjustments Underlying Task-Specific Intermittent Force Behaviors and Muscular Rhythms

Method for Detecting Quantitative Differences in the Parameters of Involuntary Effort Fluctuations in Healthy Volunteers and Patients with Parkinson’s Syndrome

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