Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “REFLEX, TENDON”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 289 records · Page 16Linked to original sources
PubMed2002

Development of a quantitative reflex hammer for measurement of tendon stretch reflex.

Quantification of tendon stretch reflex requires precise measurement of the tapping force of a reflex hammer. A quantitative reflex (QR) hammer consisting of two cut rubber pieces from a generic rubber reflex hammer and a uniaxial force transducer was constructed. Finite element stress analyses were conducted to estimate the natural frequency characteristics of the hammer and to find the stress distributions during the impact. Pendulum impact testing was conducted at four different heights to assess the calibration linearity and repeatability of the measurement. The QR hammer had a fundamental natural frequency of 515 Hz and showed minimal displacement and stress at the tip from the finite element simulation of the impact. The QR hammer also provided reliable and repeatable measurements as demonstrated with high coefficients of determination, exceeding 0.994 and small coefficients of variations, less than 4%. The calibration linearity was 0.64% compared with the reference force platform measurement. The QR hammer demonstrated sufficient accuracy and reliability for precise clinical assessment of tendon stretch reflexes.

Calibration↗
PubMed2000

Effect of lower extremity weightbearing load on motoneuron excitability in able-bodied subjects.

Body weight support (BWS) is becoming an increasingly tool popular in rehabilitation settings, but little is known about how weight support effects reflex activity. Lower extremity Hoffman (H) reflex and tendon reflex responses were used to assess motoneuron excitability as a function of static lower extremity weightbearing load in neurologically normal individuals. Factors that are known to affect reflex activity, such as body orientation, movement and task phase were kept constant. Twenty three subjects were studied under three static load conditions (50%, 75% and 100% weightbearing) using four different stimulus conditions (soleus H-reflex, soleus H-reflex with vibration, Achilles tendon reflex, quadriceps tendon reflex). Load had no effect on any of the reflexes studied; we hypothesize that under static conditions, lower extremity reflexes are not affected by superincumbent load.

Achilles Tendon↗
PubMedDate not supplied

Long-latency stretch reflex induced by tendon jerk in human triceps brachii muscle.

The electrical activity of the human triceps brachii muscle was recorded with surface electrodes in 14 healthy volunteers. Three experimental conditions were used to analyze muscle responses produced by tendon tap with an electromechanical hammer: 1) the muscle was at rest, 2) the subjects maintained an isometric tension for constant background EMG activity and 3) the subjects were asked to extend their arm in response to an acoustic signal occurring simultaneously with the tap. The analyses were performed with a computer. The monosynaptic tendon reflex had a mean latency of 12,5 ms. Later responses were observed with a mean latency of 62.8 ms. The later response observed in the extension experiments showed a synchronous EMG activity in comparison to the voluntary activity. It seems likely that proprioceptive impulses are of major importance in producing also the late responses since the method used minimalized cutaneous and joint afferent inputs.

Adolescent↗
PubMed2004

Paradoxical modulation of tendon tap reflex during voluntary contraction in Parkinson's disease.

OBJECTIVE: Inadequate supraspinal modulation of spinal motor control mechanisms such as alpha-gamma coactivation is supposed to cause difficulty in maintaining proper voluntary contraction in Parkinson's disease (PD). METHODS: Subjects were 42 patients with PD and 20 normal volunteers. Soleus H-reflex and tendon tap reflex (T-reflex) were recorded. The maximal reflexes (H(max) and T(max)) at rest were recorded first. Next, the stimulus intensities were fixed to obtain a reflex size of around 25% of M(max) at rest for both H- and T-reflexes, and the reflexes were recorded at rest, during tonic plantarflexion (TPF), and at the onset of plantarflexion. RESULTS: H(max) at rest was 55% and T(max) 30% in normal subjects, while they were 36 and 31%, respectively, in PD. The size ratio of T(max) and H(max) at rest in PD was larger than normal. In PD, the size of H-reflex increased with TPF as in normal subjects, but T-reflex decreased. These changes in T-reflex were correlated with the grade of rigidity, bradykinesia, and time for 10 m gait. H-reflex had no such correlations. CONCLUSIONS: T-reflex was abnormally modulated in PD especially during tonic contraction. SIGNIFICANCE: Inappropriate supraspinal modulation of the spinal reflex pathways disturbs motor performance in PD.

Aged↗
PubMed1990

Amplitude modulation of the human quadriceps tendon jerk reflex during gait.

Amplitude modulation of the quadriceps tendon jerk reflex was investigated during the step cycle in normal human subjects. Reflex amplitude was compared with that obtained during a control stance condition, with "equivalent" levels of EMG activity and limb position. During gait there was a progressive decrease in the reflex amplitude early in the stance phase, i.e. during yielding of the knee, and it remained reduced throughout the step cycle. This pattern of changes in reflex amplitude correlated with neither the quadriceps EMG activity nor with the knee joint movements. The behavior of the tendon reflex was similar to that described for the modulation of the quadriceps H-reflex during the early stages of the stance phase of gait. In the latter study it was argued that changes in presynaptic inhibition of quadriceps la terminals could account for the amplitude modulation. We conclude that there is no dramatic change in the gamma drive to quadriceps muscle spindles: tendon reflexes are modulated during the step cycle in much the same way as H-reflexes, in spite of the peripheral and central differences between them. Similar behavior has been described for the soleus H-reflex and Achilles tendon reflex during gait although the modulation of these reflexes followed a different pattern than that seen in the quadriceps.

Achilles Tendon↗
PubMed1973

Adrenergic control of tendon jerk reflexes in man.

1. Tendon jerk responses and H reflexes were recorded from conscious human volunteers before and after intravenous injection of methylamphetamine, thymoxamine and propranolol, and during intravenous infusion of noradrenaline.2. Methylamphetamine produced a significant increase in the amplitude of the tendon jerk, whereas noradrenaline had no effect in doses which caused a greater pressor response than methylamphetamine.3. Thymoxamine produced a dose-related reduction in the tendon jerk.4. Propranolol had no significant effect on the jerk.5. None of these drugs significantly affected the H reflex.6. It is suggested that central adrenoceptors, possibly alpha in type, exist in man, and that stimulation of these receptors facilitates tendon jerk reflexes by an action on the fusimotor system.

Blood Pressure↗
PubMed1982

[Electrophysiologic study of Achilles areflexia of aged subjects].

The elderly often presents loss of Achilles tendon reflex. In this electrophysiological study the authors examined 19 patients with loss of the ankle jerk and with no known etiology of peripheral neuropathy. They compared them with 24 subjects who had no areflexia. The study included measurement of the H reflex, of the tendon reflex, of the conduction velocity of Ia fibers and of motor conduction velocity of the tibial nerve. Amplitude of H and tendon response and H/M ratio are diminished in the areflexic group. In 4 cases the H reflex is preserved while the tendon reflex is abolished. The meaning of these impairments is discussed.

Achilles Tendon↗
PubMed1999

Reproducibility of tendon jerk reflexes during a voluntary contraction.

OBJECTIVES: The present study explored whether testing tendon jerks during voluntary contraction of the test muscle would improve reproducibility by effectively 'clamping' the excitability of the motoneurone pool at firing threshold. METHODS: Tendon jerk reflexes of soleus, tibialis anterior and vastus lateralis and the soleus H reflex were recorded in 12 healthy subjects at rest and during voluntary contractions of 10-20% of maximum. Recordings were repeated 8-10 times in 5 subjects, in whom reflex symmetry was also determined. RESULTS: Not all tendon jerk reflexes could be recorded at rest, and the variability of latency and amplitude was high. All reflexes could be recorded in each subject during contractions. The latency of tendon jerk reflexes decreased by approximately 2 ms during contractions, but H-reflex latency decreased by only 0.2-0.3 ms. For the tendon jerks, an asymmetry of >3.0 ms at rest and >2.5 ms contracting would be outside 3 SD of the normal mean. In repeat studies, the coefficient of variation of reflex latency was <4% for the tendon jerk. CONCLUSIONS: A voluntary contraction could potentiate the tendon jerk by a number of mechanisms, but the most important is probably enhancement of the excitability of the motoneurone pool. The present techniques should increase the value of tendon reflex testing when assessing possible peripheral nerve, plexus and root disturbances.

Adult↗
PubMed1992

A comparative study of methods for estimation of presynaptic inhibition.

The influence of vibration on the H-reflex and on the tendon reflex amplitudes was compared and the efficacy of both methods for the assessment of the presynaptic inhibition was studied. One hundred and twenty patients with post-stroke spastic hemiparesis were investigated. Muscle tone, muscle force and tendon reflexes were assessed. The H-reflex and the Achilles tendon reflex (TA) were recorded under identical experimental conditions. Vibration at a frequency of 100 Hz and an amplitude of 2 mm was applied to the TA. Just after vibration the maximal amplitudes of both reflexes were measured. The ratios of reflex amplitudes after vibration to normal maximal reflex amplitudes (Hvibr/Hmax and TAvibr/TAmax) were evaluated. In all patients with hemiparesis the healthy side was used as a control. Our results revealed significantly increased amplitude ratios on the spastic side. Hence it is concluded that presynaptic inhibition is decreased in spasticity. The amplitude ratios on the healthy and the spastic side were consistent. There was good positive correlation between Hvibr/Hmax and TAvibr/TAmax ratios, suggesting that they provide similar and reliable estimates of presynaptic inhibition.

Adult↗
PubMed1996

Changes in spinal reflexes preceding a voluntary movement in young and old adults.

BACKGROUND: Age-related differences in spinal excitability during response preparation were assessed by eliciting either a 50% H-reflex or an Achilles tendon reflex preceding the onset of a right plantar flexion contraction in 20 young adults (23.1 +/- 1.64 yrs) and 20 old adults (68.5 +/- 5.53 yrs). METHODS: On each simple reaction time trial, the test reflex was elicited at a specific test interval during either the foreperiod or the response period. The foreperiod test intervals were 500, 600, 700, 800, 900, and 1000 msec after the presentation of the warning stimulus. The response period test intervals were 50, 100, 150, 200, 250, and 300 msec after the presentation of the response stimulus. Control reflexes were randomly elicited between the simple reaction time trials. RESULTS: Changes in reflex excitability were not observed during the foreperiod in either age group. During the response period, the percentage of H-reflex facilitation as compared to control H-reflexes was similar for the young (68%) and the old (61%) adults, but the magnitude of Achilles tendon reflex facilitation with respect to control reflex responses was greater in the young adults (74%) than in the old adults (38%). The time course of H- and tendon reflex facilitation was delayed in the old group during the response period. CONCLUSIONS: The results indicate that processes underlying the preparation and generation of a motor response are similar in young and old adults. However, these processes occur at a slower rate in old adults.

Achilles Tendon↗