Modulation of reflex EMG and stiffness in response to stretch of human finger muscle.

Akazawa, Kenzo; Milner, Theodore E.; Rb, Stein

doi:10.1152/jn.1983.49.1.16

Cited by 280 publications

(124 citation statements)

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“…6) was dominated by a velocity sensitivity in series with a time delay. Many studies under similar conditions of pertubation have shown that reflexive feedback is dominated by a velocity sensitivity as the result of Ia muscle spindle feedback [1], [4]- [6], [24].…”

Section: Observed Behaviormentioning

confidence: 99%

Design of Perturbation Signals for the Estimation of Proprioceptive Reflexes

Schouten

Vlugt

Helm

2008

IEEE Trans. Biomed. Eng.

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Abstract-This study aimed to identify the functional contribution of reflexes to human motor control during posture maintenance. Continuous random force disturbances were applied at the hand while the subjects were instructed to minimize the deviation resulting from the force disturbances. The results were analyzed in the frequency domain with frequency response functions (FRFs). Two FRFs were evaluated: 1) the mechanical admittance and 2) the reflexive impedance, expressing the dynamic relation between position and muscle activation (assessed via electromyography, EMG). The reflexive impedance is a direct measure of the proprioceptive reflexes. To record all relevant dynamical characteristics of the arm, wide bandwidth signals were used as force disturbance. Distributing the power of the signal over fewer frequencies within the bandwidth improved the signal-to-noise-ratio SNR of the EMG recordings, facilitating reliable estimation of the reflexive impedance. The coherence indicated that the relation between force disturbance and EMG is linear under the given conditions and improved with the SNR. The method of designing disturbance signals and the estimation of the reflexive impedance are useful for studies aiming to quantify proprioceptive reflexes and to investigate its functionality.

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Section: Observed Behaviormentioning

confidence: 99%

Design of Perturbation Signals for the Estimation of Proprioceptive Reflexes

Schouten

Vlugt

Helm

2008

IEEE Trans. Biomed. Eng.

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“…To obtain sufficient positional accuracy of the endeffectors (hands, fingers, or tools) the arm and shoulder girdle need to be stabilised by means of muscular activity. Stability in the proximal upper extremity joints can be achieved by co-contraction of muscles spanning these joints (Akazawa et al 1983). In addition, in the distal joints increased precision demands may coincide with increased cocontraction.…”

Section: Introductionmentioning

confidence: 99%

Effects of precision demands and mental pressure on muscle activation and hand forces in computer mouse tasks

Visser

Looze

Graaff³

et al. 2004

Ergonomics

116

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The objective of the present study was to gain insight into the effects of precision demands and mental pressure on the load of the upper extremity. Two computer mouse tasks were used: an aiming and a tracking task. Upper extremity loading was operationalized as the myo-electric activity of the wrist flexor and extensor and of the trapezius descendens muscles and the applied grip-and click-forces on the computer mouse. Performance measures, reflecting the accuracy in both tasks and the clicking rate in the aiming task, indicated that the levels of the independent variables resulted in distinguishable levels of accuracy and work pace. Precision demands had a small effect on upper extremity loading with a significant increase in the EMG-amplitudes (21%) of the wrist flexors during the aiming tasks. Precision had large effects on performance. Mental pressure had substantial effects on EMG-amplitudes with an increase of 22% in the trapezius when tracking and increases of 41% in the trapezius and 45% and 140% in the wrist extensors and flexors, respectively, when aiming. During aiming, grip-and click-forces increased by 51% and 40% respectively. Mental pressure had small effects on accuracy but large effects on tempo during aiming. Precision demands and mental pressure in aiming and tracking tasks with a computer mouse were found to coincide with increased muscle activity in some upper extremity muscles and increased force exertion on the computer mouse. Mental pressure caused significant effects on these parameters more often than precision demands. Precision and mental pressure were found to have effects on performance, with precision effects being significant for all performance measures studied and mental pressure effects for some of them. The results of this study suggest that precision demands and mental pressure increase upper extremity load, with mental pressure effects being larger than precision effects. The possible role of precision demands as an indirect mental stressor in working conditions is discussed.

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“…Co-contraction, nevertheless, does occur in a number of situations that require a high stability of the joint that the muscles are acting on, as for instance when learning a new motor task or when stabilizing a joint to prevent external mechanical perturbations (Smith, 1981). In the latter case large stretch reflexes would appear to be appropriate, as the stretch reflex has been shown to contribute to muscle stiffness (Nichols & Houk, 1976;Akazawa, Milner & Stein, 1983). One way of achieving this could be by decreasing presynaptic inhibition acting on the central terminals of the Ia afferents, which convey the stretch reflex.…”

Section: Introductionmentioning

confidence: 99%

The regulation of presynaptic inhibition during co‐contraction of antagonistic muscles in man.

Nielsen¹,

Kagamihara²

1993

The Journal of Physiology

212

144

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SUMMARY1. The size of the soleus, tibialis anterior and medial gastrocnemius H reflexes were measured at different levels of EMG activity in ankle plantar-and dorsiflexors. At similar levels of EMG activity in the agonist muscle, the soleus and tibialis anterior H reflexes were found to be smaller during co-contraction than during an isolated agonist contraction. In contrast to this, the medial gastrocnemius H reflex had the same size during co-contraction as during an isolated plantarflexion at comparable EMG levels.2. Peaks occurred at monosynaptic reflex latency in the post-stimulus time histogram (PSTH) of firing of soleus and tibialis anterior motor units following stimulation of their respective motor nerves. These homonymous Ia peaks were found to be smaller during co-contraction than during isolated agonist contraction, whereas that of medial gastrocnemius motor units was unchanged. As the monosynaptic peak in the PSTH may give an indirect measure of the size of the monosynaptic EPSP in the motoneurone, it is suggested that these findings reflect a differential control of presynaptic inhibition of soleus and tibialis anterior motor units with respect to medial gastrocnemius motor units.3. The monosynaptic Ia facilitation of the soleus H reflex evoked by a stimulation of the femoral nerve, was also found to be smaller during cocontraction of tibialis anterior and soleus than during isolated plantarflexion. This suggests that presynaptic inhibition of heteronymous I a fibres from the quadriceps muscle projecting to soleus motoneurones is regulated in the same way as presynaptic inhibition of homonymous I a fibres during co-contraction.4. The femoral nerve-induced monosynaptic facilitation of the soleus H reflex was found to decrease with increasing tonic levels of both co-contraction and isolated dorsi-and plantarflexion. The amount of facilitation decreased to the same degree with increasing levels of dorsiflexion and co-contraction. For the same level of EMG in the dorsiflexors there was thus no difference in the amount of facilitation whether the dorsiflexors were activated separately or in a co-contraction.

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Modulation of reflex EMG and stiffness in response to stretch of human finger muscle.

Cited by 280 publications

References 0 publications

Design of Perturbation Signals for the Estimation of Proprioceptive Reflexes

Design of Perturbation Signals for the Estimation of Proprioceptive Reflexes

Effects of precision demands and mental pressure on muscle activation and hand forces in computer mouse tasks

The regulation of presynaptic inhibition during co‐contraction of antagonistic muscles in man.

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