Electromyographic responses to imposed sinusoidal movement of the human thumb.

Brown, Tamara L.; Rack, P. M. H.; Ross, H. F.

doi:10.1113/jphysiol.1982.sp014402

Cited by 23 publications

(10 citation statements)

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“…Studies in the cat have shown similar discrete bursts of activity phase-locked to cyclic stretching which became more probable as the amplitude of the stretch increased (Jansen and Rack 1966;Rosenthal et al 1970) and human studies also have shown EMG traces in which such saturation was apparent (e.g. Brown et al 1982b). Brown et al commented on the EMG being "well modulated by movement" (p. 95) in the 5 -15 Hz range.…”

Section: Discussionmentioning

confidence: 98%

“…The saturation of the motor neuron modulation occurred at higher frequencies because the gain of the EMG reflex response increases as a power function (exponent > 1) of frequency (Cathers et al 1999) to about 10 Hz (Neilson 1972a,b;Neilson and Neilson 1978;Zahalak and Heyman 1979;Zahalak 1981, 1993;Cathers et al 1999). Beyond 10 Hz, the reflex gain decreases and this may be the result of saturation (Brown et al 1982b;Matthews 1993). …”

Section: Discussionmentioning

confidence: 99%

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Entrainment to extinction of physiological tremor by spindle afferent input

2005

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In this study the systematic modulation of wrist flexor muscle activity by imposed joint movement was examined. Ten subjects maintained a constant contraction level (25% of maximum; trial duration: 20 s) in flexor carpi radialis while their wrists were perturbed with 50 different quasi-sinusoidal signals (frequency range: 0.5 -9.5 Hz; amplitude: 0.3° -4.2°). Frequency spectra of wrist position and the rectified and filtered electromyogram (EMG) were determined. The muscle activity was only weakly entrained to imposed movements of small amplitude and low frequency, as shown by a small peak in the EMG spectrum at the frequency of movement, while the most prominent peak in the spectrum was between 9 -15 Hz, corresponding to the frequency range of physiological tremor. The entrainment of muscle activity increased markedly as the amplitude and frequency of the imposed movement increased, to the point of saturation of modulation and harmonic peaks in the spectrum. In parallel with this increase in entrainment, the 9 -15 Hz tremor peak was progressively extinguished. The results are consistent with a coupled oscillator model in which the central oscillatory source(s) of tremor became fully entrained to the imposed movement at the highest amplitudes and frequencies. Such coupling depends on communication between the external forcing oscillator and the central oscillator(s), the Ia afferent signal from the imposed movement being the most likely candidate to provide the entraining signal for the central oscillator(s).

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Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

Entrainment to extinction of physiological tremor by spindle afferent input

2005

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“…In earlier studies of the wrist flexors with individual ramp-type stretches the delayed response was very greatly reduced on increasing the repetition rate from 041 to 1 Hz (Rothwell, Day, Beradelli & Marsden, 1986). However, that of flexor pollicis longus was much less affected (see also, Brown et al 1982). Conceivably, this betokens yet further subdivisions of the reflex.…”

Section: Wider Implicationsmentioning

confidence: 92%

“…In the monkey, the EMG modulation of the stretch reflex of jaw muscles increases up to 20 Hz, and no peculiarities were commented upon for frequencies up to 50 Hz (Goodwin, Hoffman & Luschei, 1978). The response of the human flexor pollicis longus tends to decrease above 12 Hz (Brown, Rack & Ross, 1982), while that of triceps surae does not so obviously do so (Agarwal & Gottlieb, 1977;Evans et al 1983). A point of possible significance is that in some of these experiments there was little tonic EMG activity between the phasic EMG bursts elicited by the stretching; in effect, a series of semi-isolated excitatory responses were being studied.…”

Section: Relation To Previous Gross Emg Recordingsmentioning

confidence: 99%

Interaction between short‐ and long‐latency components of the human stretch reflex during sinusoidal stretching.

Matthews¹

1993

The Journal of Physiology

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SUMMARY1. Using wrist muscles, the subdivision of the human stretch reflex into separate components was examined with small amplitude sinusoidal stretching of relatively high frequency (10-40 Hz). The reflex was evoked by angular rotation of the wrist (below 1 deg amplitude), applied via the hand during maintained voluntary contraction of the muscle studied; both flexors and extensors were tested.2. The reflex response was recorded electromyographically rather than mechanically. For each condition, the surface EMG was rectified and averaged to give a cycle average showing the mean response evoked by a cycle of stretching. The cycle average was fitted with a sinusoid, the amplitude and phase of which were used to assess the reflex; their value reflects the combined action of its various subcomponents. Fourier analysis gave similar results (the EMG was then rectified but not averaged).3. The amplitude of the reflex response typically fell to a minimum in the region of 20-25 Hz. The phase lag of the response in relation to the stimulus increased approximately linearly with frequency, except in the region of the amplitude minimum. Here the lag tended to remain constant, or to decrease slightly; this created a discontinuity between the upper and lower limbs of the phase plot.4. Such effects are attributed to an interaction between two components of the reflex that differ in latency by 20-25 ms. These would progressively change their relative phase as the frequency increased. At first they would come to interfere with each other, but then the more delayed reflex produced by a given cycle of stretching would begin to sum with the shorter latency reflex evoked by the next stretch.5. At high and low frequencies the cycle averages were normally well fitted by a single sinusoid. Around 20-25 Hz, however, they typically showed appreciable harmonic distortion, with the second harmonic larger than the fundamental. The cycle average then showed two separate responses per cycle of stretching. These were considered to represent the uncancelled non-linear residua of separate components of the reflex response. Their relative timing shifted appropriately with change of frequency.6. These 'double responses' are unlikely to be due to mechanical resonance. First, the relative sizes of the two components could be altered by the reflex action of cutaneous afferents. Second, the same pattern of behaviour was found when the MS 1143 P. B. C. MATTHEWS mechanical stimuli were applied directly to the tendon of flexor carpi radialis while the hand remained fixed.7. Sinusoidal stretching thus provides an alternative to ramp stretching for fractionating the stretch reflex into components of different latency. A longer latency component has thereby been found to persist at frequencies above those at which muscle can respond mechanically; its central machinery can thus be expected to take part in the moment to moment control of muscle action.

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“…Electromyograms were recorded from over the surface of flexor pollicis longus (see Brown et al 1982b). Force, position and e.m.g.…”

Section: Methodsmentioning

confidence: 99%

Different types of tremor in the human thumb.

Brown¹,

Rack²,

Ross³

1982

The Journal of Physiology

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1. The upper limbs of normal subjects were immobilized in a way that allowed measurement of forces and movements at the thumb interphalangeal joint without significant movement elsewhere in the limb. 2. When the subject attempted to maintain a steady flexing force at the joint against a rigid stop, the actual force showed the irregular 8‐11 Hz fluctuations characteristic of a ‘physiological tremor'. This force fluctuation increased when the mean flexing force increased. 3. If the subject exerted his flexing force against a light complaint spring, there was an analogous irregular 8‐11 Hz movement at the joint. 4. When, however, an extra inertial load was added to the terminal phalanx, flexion against a complaint spring was often accompanied by a different type of tremor. This was a more regular oscillation, of lower frequency (3‐6 Hz), and of much larger amplitude. 5. The precise frequency and amplitude of this type of tremor depended on the characteristics of the added inertia and spring, in a way that could have been predicted from the responses of the joint to an imposed sinusoidal movement (Brown, Rack & Ross, 1982a). The movement appeared to arise from re‐excitation within stretch reflex pathways. 6. The irregular 8‐11 Hz tremor at this joint could not be attributed to reflex re‐excitation, since the responses to sinusoidal movement indicated a stretch reflex whose timing would not support a movement at that frequency. It is, however, emphasized that other joints of the hand and fingers may behave in different ways.

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Electromyographic responses to imposed sinusoidal movement of the human thumb.

Cited by 23 publications

References 14 publications

Entrainment to extinction of physiological tremor by spindle afferent input

Entrainment to extinction of physiological tremor by spindle afferent input

Interaction between short‐ and long‐latency components of the human stretch reflex during sinusoidal stretching.

Different types of tremor in the human thumb.

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