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BMC Musculoskeletal Disorders Nov 2016Limited research suggests elite athletes may differ from non-athletes in clinical tendon tap reflex responses.
BACKGROUND
Limited research suggests elite athletes may differ from non-athletes in clinical tendon tap reflex responses.
METHODS
In this matched cohort study, 25 elite rugby league athletes were compared with 29 non-athletes to examine differences in tendon reflex responses. Relationships between reflex responses and lengths of players' careers were also examined. Biceps, triceps, patellar and Achilles tendon reflexes were clinically assessed.
RESULTS
Right and left reflexes were well correlated for each tendon (r = 0.7-0.9). The elite rugby league athletes exhibited significantly weaker reflex responses than non-athletes in all four tendons (p < 0.005). Biceps reflexes demonstrated the largest difference and Achilles reflexes the smallest difference. Moderate negative correlations (r = -0.3-0.6) were observed between reflex responses and lengths of players' careers.
CONCLUSIONS
Future research is required to further elucidate mechanisms resulting in the observed differences in tendon reflexes and to ensure clinical tendon tap examinations and findings can be interpreted appropriately in this athletic population.
Topics: Adult; Cohort Studies; Football; Humans; Male; Reflex, Stretch; Time Factors; Young Adult
PubMed: 27809816
DOI: 10.1186/s12891-016-1305-3 -
American Journal of Physiology.... Jul 2006This study was conducted to examine reflex mechanisms that mediate urinary bladder and external urethral sphincter (EUS) coordination in urethane-anesthetized female...
This study was conducted to examine reflex mechanisms that mediate urinary bladder and external urethral sphincter (EUS) coordination in urethane-anesthetized female Sprague-Dawley rats. We investigated the properties of EUS reflexes elicited by electrical stimulation of pelvic nerve afferent axons (pelvic-EUS reflex). The changes in the reflexes induced by bladder distension and administration of agonists or antagonists for glutamatergic or serotonergic receptors were examined. The reflexes consisted of an early response (ER, 18- to 22-ms latency) and a late, long-duration (>100-ms latency) response (LR), which consisted of bursts of activity at 20- to 160-ms interburst intervals. In a few experiments, a reflex with an intermediate (40- to 70-ms) latency was also identified. With the bladder empty, the ER, but not the LR, was detected in the majority of experiments. The LR was markedly enhanced when the bladder was distended. The ER remained, but the LR was abolished, after spinal cord transection at T8-T9. The ER and LR were significantly decreased 75 and 35%, respectively, by the N-methyl-D-aspartate receptor antagonist MK-801 (0.3 mg/kg iv), but only decreased 18 and 14%, respectively, by the alpha-amino-5-methylisoxazole-4-propionate receptor antagonist LY-215490 (3 mg/kg iv). The serotonin (5-HT1A) receptor agonist 8-hydroxy-2-(di-n-propylamino)-tetralin (1 mg/kg iv) enhanced spontaneous EUS activity and the pelvic-EUS reflex. WAY-100635 (0.1-1 mg/kg iv), a 5-HT1A antagonist, reversed the effect of 8-hydroxy-2-(di-n-propylamino)-tetralin and suppressed EUS activity and the pelvic-EUS reflex. These results indicate that glutamatergic and serotonergic mechanisms are important in the reflex pathways underlying bladder- sphincter coordination in rats.
Topics: 8-Hydroxy-2-(di-n-propylamino)tetralin; Animals; Evoked Potentials; Excitatory Amino Acid Agents; Female; Piperazines; Pyridines; Rats; Rats, Sprague-Dawley; Receptor, Serotonin, 5-HT1A; Receptors, Neurotransmitter; Reflex; Serotonin; Urethane; Urethra
PubMed: 16469836
DOI: 10.1152/ajpregu.00780.2005 -
Psychophysiology Feb 2018During threat of shock, the startle reflex is potentiated, suggesting modulation by defensive mobilization. To determine whether startle potentiation is specific to...
During threat of shock, the startle reflex is potentiated, suggesting modulation by defensive mobilization. To determine whether startle potentiation is specific to aversive anticipation, startle reflexes were measured in the context of either aversive or appetitive anticipation in a between-subject study. Participants wore a device on the wrist that could deliver electrical shock (n = 49), or vibrotactile stimulation indicating monetary reward (n = 48). Cues signaling "threat" or "safe" periods were presented alone, or accompanied by presentation of affective and neutral pictures on half of the trials. Results indicated that the startle reflex was significantly potentiated when anticipating either shock or reward, compared to safe periods, both when no picture was presented, as well as during picture viewing. The difference between threat and safety in both reflex magnitude and skin conductance changes was larger for those anticipating shock, suggesting that the aversive context was more motivationally engaging. The pattern of reflex modulation as a function of picture valence varied under threat and safety, but was identical in the shock and reward groups, consistent with a hypothesis that anticipation of either aversive or appetitive events prompts heightened perceptual vigilance, potentiating the acoustic startle reflex.
Topics: Anticipation, Psychological; Anxiety; Electric Stimulation; Electromyography; Emotions; Female; Galvanic Skin Response; Humans; Male; Photic Stimulation; Reflex, Startle; Reward
PubMed: 28881032
DOI: 10.1111/psyp.12989 -
Neurology Aug 2015Uncertainty in diagnosing disorders of consciousness, and specifically in determining whether consciousness has been lost or retained, poses challenging scientific and...
Uncertainty in diagnosing disorders of consciousness, and specifically in determining whether consciousness has been lost or retained, poses challenging scientific and ethical questions. Recent neuroimaging-based tests for consciousness have cast doubt on the reliability of behavioral criteria in assessing states of consciousness and generate new questions about the assumptions used in formulating coherent diagnostic criteria. The reflex, a foundational diagnostic tool, offers unique insight into these disorders; behaviors produced by unconscious patients are thought to be purely reflexive, whereas those produced by conscious patients can be volitional. Further investigation, however, reveals that reflexes cannot be reliably distinguished from conscious behaviors on the basis of any generalizable empirical characteristics. Ambiguity between reflexive and conscious behaviors undermines the capacity of the reflex to distinguish between disorders of consciousness and has implications for how these disorders should be conceptualized in future diagnostic criteria.
Topics: Consciousness; Consciousness Disorders; Humans; Reflex; Reproducibility of Results
PubMed: 26085602
DOI: 10.1212/WNL.0000000000001748 -
IEEE Transactions on Neural Systems and... Jun 2020Post-stroke flexion synergy limits arm/hand function and is also linked to hyperactive stretch reflexes or spasticity. It is implicated in the increased role of indirect...
Post-stroke flexion synergy limits arm/hand function and is also linked to hyperactive stretch reflexes or spasticity. It is implicated in the increased role of indirect motor pathways following damage to direct corticospinal projections. We hypothesized that this maladaptive neuroplasticity also affects stretch reflexes. Specifically, multi-synaptic interactions in indirect motor pathways may increase nonlinear neural connectivity and time lag between stretch and reflex muscle response. Continuous position perturbations were applied to the elbow joint when eleven participants with stroke generated two levels of shoulder abduction (SABD) torques with their paretic arm to induce synergy-related spasticity. Likewise, the perturbations were applied to eleven control subjects while performing SABD and elbow flexion levels matching the synergy torques in stroke. We quantified linear and non-linear connectivity and the corresponding time lags between perturbations and muscle activity. Enhanced nonlinear connectivity with a prolonged time lag was found in stroke as compared to controls. Non-linear connectivity and time lag also increased with the expression of the flexion synergy, as induced by greater SABD load levels, in stroke. This study provides new evidence of changes in neural connectivity and long-latency time lag in the stretch reflex response post-stroke. The results suggest the contribution of indirect motor pathways to synergy-related spasticity.
Topics: Elbow; Electromyography; Humans; Muscle, Skeletal; Range of Motion, Articular; Reflex; Reflex, Stretch; Stroke
PubMed: 32275603
DOI: 10.1109/TNSRE.2020.2986304 -
Neuroscience Apr 2020Inter-limb reflexes play an important role in coordinating behaviors involving different limbs. Previous studies have demonstrated that human elbow muscles express an...
Inter-limb reflexes play an important role in coordinating behaviors involving different limbs. Previous studies have demonstrated that human elbow muscles express an inter-limb stretch reflex at long-latency (50-100 ms), a timing consistent with a trans-cortical linkage. Here we probe for inter-limb stretch reflexes in the shoulder muscles of human participants. Unexpected torque pulses displaced one or both shoulders while participants adopted a steady posture against background torques. The results demonstrated inter-limb stretch reflexes occurring at short-latency for both shoulder extensors and flexors; the rapid timing (36-50 ms) must involve a spinal linkage for the two arms. Inter-limb stretch reflexes were also observed at long-latency yet they were opposite to the preceding short-latency; when the short-latency stretch reflex was excitatory then the long-latency stretch reflex was inhibitory and vice versa. Comparing the responses to contralateral arm displacement to those during simultaneous displacement of both arms revealed that inhibitory inter-limb stretch reflexes are independent of within-limb stretch reflexes, but that excitatory inter-limb stretch reflexes are suppressed by within-limb stretch reflexes. Our results provide the first demonstration of short-latency inter-limb stretch reflexes in the upper limb of humans and reveal interacting spinal circuits for within-limb and inter-limb stretch reflexes.
Topics: Electromyography; Humans; Muscle, Skeletal; Reflex; Reflex, Stretch; Shoulder; Torque; Upper Extremity
PubMed: 32062020
DOI: 10.1016/j.neuroscience.2020.02.007 -
The Journal of Physiology Nov 19961. Experiments were carried out to test the effect of changes in spindle resting discharge on the size of monosynaptic reflexes in the cat and on the H reflex in humans....
1. Experiments were carried out to test the effect of changes in spindle resting discharge on the size of monosynaptic reflexes in the cat and on the H reflex in humans. Resting discharge was altered by contracting the triceps surae muscle at longer (hold-long) or shorter (hold-short) lengths than that at which the reflex was tested. 2. The reflex in the cat was larger after hold-long than after hold-short conditioning, and the difference, after an initial decline, was well maintained. For the human H reflex a similar pattern was observed except that 15 s after muscle conditioning the difference in reflex size had disappeared. 3. Monosynaptic reflex depression immediately after hold-long conditioning, when most of the muscle spindles are silent, was attributed to the high level of spindle discharge during the immediately preceding hold-long period. The time course of this inhibition was too long to be accounted for by presynaptic inhibition. 4. In the cat heteronymous muscle conditioning was used to test whether presynaptic inhibition could be responsible for reflex depression using the synergist muscle pair lateral gastrocnemius-soleus and medial gastrocnemius. Conditioning one of the pair did not affect the reflex in the other, the opposite result to that expected with presynaptic inhibition. A similar experiment in which the triceps H reflex in human subjects was facilitated by a quadriceps volley gave the same result. 5. Thus this study presents evidence that monosynaptic reflexes are depressed by the on-going discharge of muscle spindles in the homonymous muscle, but that this depression does not appear to involve "classical' presynaptic inhibition.
Topics: Adult; Animals; Cats; Electric Stimulation; Electrophysiology; Evoked Potentials; Female; H-Reflex; Humans; Male; Muscle Contraction; Muscles; Reflex, Monosynaptic; Spinal Nerve Roots
PubMed: 8951729
DOI: 10.1113/jphysiol.1996.sp021767 -
The Journal of Physiology May 2001Although numerous treatments have been found to improve locomotion in spinal cord injured mammals, the underlying mechanisms are very poorly understood. Some of the main... (Review)
Review
Although numerous treatments have been found to improve locomotion in spinal cord injured mammals, the underlying mechanisms are very poorly understood. Some of the main possibilities are: (1) regeneration of axons across the injury site and the re-establishment of descending pathways needed to voluntarily initiate and maintain stepping in the hind legs, (2) enhanced effectiveness of undamaged neurons in preparations with incomplete transections of the cord, (3) non-specific facilitation of reflexes and intrinsic spinal networks by transmitters released from regenerated axons and/or by substances introduced by the treatment, and (4) enhanced trunk movements close to the injury site strengthening the mechanical coupling of the trunk to the hind legs via spinal reflexes. In addition, any procedure that even slightly improves stepping may be further enhanced by use-dependent modification of reflex pathways and interneuronal networks in the lumbar cord. The emphasis of this review is on the contribution of spinal reflexes to the patterning of motor activity for walking, and how enhancing reflex function may contribute to the improvement of locomotion by treatments aimed at restoring locomotion after complete transection of the spinal cord.
Topics: Animals; Locomotion; Recovery of Function; Reflex; Spinal Cord Injuries
PubMed: 11351015
DOI: 10.1111/j.1469-7793.2001.0075b.x -
[Clinical techniques for use in neurological physical examinations. II. Motor and reflex functions].Revista de NeurologiaThe aim of this study is to highlight the chief practical aspects of the techniques used in the neurological physical examination of the motor and reflex functions. (Review)
Review
AIMS
The aim of this study is to highlight the chief practical aspects of the techniques used in the neurological physical examination of the motor and reflex functions.
DEVELOPMENT
We recommend clinicians to carry out a brief but consistent and effective exploration in a systematic, flexible and orderly manner to check for abnormalities in the motor and reflex functions of the nervous system. Should any anomalies be detected, then a more detailed and thorough neurological exploration must be performed selectively. We present a detailed review of the practical aspects of the main techniques used in the physical examination of these neurological categories. The motor function is explored using techniques that examine muscle tone, muscle strength, muscle fatigability, hypokinesia, tremor, coordination and gait. Lastly, in this category several manoeuvres that are useful in hysterical or mimicking paralyses are also dealt with. Reflexes to examination are usually divided into: 1. Myotatic reflexes; 2. Cutaneomucous reflexes; 3. Spinal cord or defence automatism reflexes; 4. Posture and attitude reflexes. We also add the study of primitive pathological reflexes, remote reflexes, synkinesias and signs of meningeal irritation.
CONCLUSIONS
We present a detailed description of the main clinical techniques used in the neurological physical examination of motility and reflexes, as well as an approach that allows them to be performed on adult patients. In addition, we underline the importance of physically examining the nervous system in contemporary medicine and the need to continually perfect the way these techniques are performed in order to achieve an efficient clinical practice.
Topics: Humans; Motor Activity; Muscle, Skeletal; Neurologic Examination; Neuromuscular Diseases; Physical Examination; Reflex
PubMed: 15543502
DOI: No ID Found -
PloS One 2015Presynaptic inhibition (PSI) has been shown to modulate several neuronal pathways of functional relevance by selectively gating the connections between sensory inputs... (Clinical Trial)
Clinical Trial
Presynaptic inhibition (PSI) has been shown to modulate several neuronal pathways of functional relevance by selectively gating the connections between sensory inputs and spinal motoneurons, thereby regulating the contribution of the stretch reflex circuitry to the ongoing motor activity. In this study, we investigated whether a differential regulation of Ia afferent inflow by PSI may be associated with the performance of two types of plantarflexion sensoriomotor tasks. The subjects (in a seated position) controlled either: 1) the force level exerted by the foot against a rigid restraint (force task, FT); or 2) the angular position of the ankle when sustaining inertial loads (position task, PT) that required the same level of muscle activation observed in FT. Subjects were instructed to maintain their force/position at target levels set at ~10% of maximum isometric voluntary contraction for FT and 90° for PT, while visual feedback of the corresponding force/position signals were provided. Unconditioned H-reflexes (i.e. control reflexes) and H-reflexes conditioned by electrical pulses applied to the common peroneal nerve with conditioning-to-test intervals of 21 ms and 100 ms (corresponding to D1 and D2 inhibitions, respectively) were evoked in a random fashion. A significant main effect for the type of the motor task (FT vs PT) (p = 0.005, η2p = 0.603) indicated that PTs were undertaken with lower levels of Ia PSI converging onto the soleus motoneuron pool. Additionally, a significant interaction between the type of inhibition (D1 vs D2) and the type of motor task (FT vs PT) (p = 0.038, η2p = 0.395) indicated that D1 inhibition was associated with a significant reduction in PSI levels from TF to TP (p = 0.001, η2p = 0.731), whereas no significant difference between the tasks was observed for D2 inhibition (p = 0.078, η2p = 0.305). These results suggest that D1 and D2 inhibitions of the soleus H-reflex are differentially modulated during the performance of plantarflexion FT and PT. The reduced level of ongoing PSI during PT suggests that, in comparison to FT, there is a larger reliance on inputs from muscle spindles primary afferents when the neuromuscular system is required to maintain position-controlled plantarflexion contractions.
Topics: Adult; Electromyography; Female; H-Reflex; Healthy Volunteers; Humans; Male; Motor Neurons; Muscle Contraction; Muscle, Skeletal; Reflex, Stretch; Young Adult
PubMed: 26599909
DOI: 10.1371/journal.pone.0143862