Electromyographic reflexes evoked in human wrist flexors by tendon extension and by displacement of the wrist joint.

Cody, F. W. J.; Plant, Tony M.

doi:10.1113/jphysiol.1989.sp017579

Cited by 11 publications

(12 citation statements)

References 19 publications

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“…The effectiveness of the afferent Ia volley was usually greater on homonymous than on heteronymous motoneurones, as reflected by the probability ratio being greater than unity in most cases. This pattern of stronger homonymous facilitation is similar to that observed in the cat wrist musculature (Fritz et al 1989;Willis et al 1966) and the human FCR and FCU (Cody and Plant 1989).…”

Section: Heteronymous Connectionssupporting

confidence: 83%

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Synaptic connections from large afferents of wrist flexor and extensor muscles to synergistic motoneurones in man

Chalmers

Bawa

1997

Exp Brain Res

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Short-latency excitatory Ia reflex connections were determined between pairs of human wrist flexor and extensor muscles. Spindle Ia afferents were stimulated by either tendon tap or electrical stimulation. The activity of voluntarily activated single motor units was recorded intramuscularly from pairs of wrist flexor or extensor muscles. Cross-correlation between stimuli and the discharge of the motor units provided a measure of the homonymous or heteronymous excitatory input to a motoneurone. Homonymous motoneurone facilitation was generally stronger than that of the heteronymous motoneurones. The principal wrist flexors, flexor carpi radialis (FCR) and flexor carpi ulnaris (FCU), were tightly connected through a bidirectional short-latency reflex pathway. In contrast, the extensor carpi ulnaris (ECU) and the extensor carpi radialis (ECR) did not have similar connections. ECU motoneurones received no short-latency excitatory Ia input from the ECR. ECR motoneurones did receive excitatory Ia input from ECU Ia afferents; however, its latency was delayed by several milliseconds compared with other heteronymous Ia excitatory effects observed. The wrist and finger extensors were linked through heteronymous Ia excitatory reflexes. The reflex connections observed in humans are largely similar to those observed in the cat, with the exception of heteronymous effects from the ECU to the ECR and from the extensor digitorum communis (EDC) to the ECU, which are present only in humans. The differences in the reflex organization of the wrist flexors versus the extensors probably reflects the importance of grasping.

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Section: Heteronymous Connectionssupporting

confidence: 83%

“…Cody and Plant 1989;Malmgren and Pierrot-Deseilligny 1988). The goal of the present study was to determine the excitatory projections of large muscle afferents from the major wrist flexor and extensor muscles in humans to determine monosynaptic connections linking these muscles.…”

Section: Introductionmentioning

confidence: 99%

Synaptic connections from large afferents of wrist flexor and extensor muscles to synergistic motoneurones in man

Chalmers

Bawa

1997

Exp Brain Res

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“…This meant that the short and long latency EM G burst, due to muscle re¯exes, might not have been detected and that voluntary contractions were measured for long build-up times (> 300 ms). Cody and Plant (1989) showed that the amplitude of the short latency component decreased, when velocity of tendon extension decreased. If the amplitude of the short latency component became too small when build-up time increased, then this com ponent might not have been detected since the current study used an arbitrary threshold level to determine the occurrence of EM G bursts.…”

Section: Discussionmentioning

confidence: 99%

“…Although there were variations among muscles and methodologies used, reported short EM G latency was 25 to 50 ms, long EM G latency was 45 to 80 ms, and EM G latency longer than 100 ms was considered as voluntary activity (Agarwal and Gottlieb 1977, Balestra et al 1992, Cody and Plant 1989, Gielen et al 1988). Based on these previous studies, the EM G latency measured for a 35 ms build-up tim e seemed to be mainly from the involuntary re¯ex response.…”

Section: Discussionmentioning

confidence: 99%

The influence of target torque and torque build-up time on physical stress in right angle nutrunner operation

Radwin²

1998

Ergonomics

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This study used a computer-controlled electric right angle nutrunner to investigate the relative eOE ects of diOE erent power hand tool and process parameters on operator muscular exertions, handle stability and subjective ratings of perceived exertion. Target torque (25, 40 and 55 Nm), torque build-up time (35, 150, 300, 500 and 900 ms), and workstation orientation (horizontal and vertical) were studied. Dependent variables included EM G activity of the ® nger¯exors, biceps, and triceps, handle velocity and displacement, work done on the tool-hand system and power involved in doing work, subjective ratings of perceived exertion, and task acceptance. Six inexperienced subjects (three females and three males) participated. Ten replications were performed for each combination of experimental conditions. The consequences of increasing the torque reaction force were greater handle instability and perceived exertion. The eOE ect of torque buildup time on handle kinematics, muscular activity and perceived exertion was not monotonic. Among ® ve build-up times tested, the hand was most unstable (greater peak handle velocity and power against the operator) for a 150 ms buildup time. Greater peak handle displacement, total work against the operator and average EM G were observed for 150 and 300 ms build-up times than for other build-up time conditions. Integrated EM G and EM G latency signi® cantly increased as build-up time increased. Average EM G latency between the onset of EM G burst and the onset of torque build-up was 40 ms for a 35 ms build-up time and 330 ms for a 900 ms build-up time. Subjective ratings of perceived exertion were the least when torque build-up time was 35 ms, however greater peak torque variance was associated with this condition.

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“…It is thus important that similar types of frequency response were obtained from flexor carpi radialis (FCR) when the mechanical stimulus was applied directly to its tendon, which was displaced transversely while the hand remained fixed. This stretches the muscle and produces typical stretch reflexes with ramp stimuli (Cody & Plant, 1989). Figure 4 shows the frequency response elicited by such direct stretching.…”

Section: Tendon Stimulationmentioning

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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Electromyographic reflexes evoked in human wrist flexors by tendon extension and by displacement of the wrist joint.

Cited by 11 publications

References 19 publications

Synaptic connections from large afferents of wrist flexor and extensor muscles to synergistic motoneurones in man

Synaptic connections from large afferents of wrist flexor and extensor muscles to synergistic motoneurones in man

The influence of target torque and torque build-up time on physical stress in right angle nutrunner operation

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

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