scholarly journals Muscle Stiffness and Spinal Stretch Reflex Sensitivity in the Triceps Surae

2008 ◽  
Vol 43 (1) ◽  
pp. 29-36 ◽  
Author(s):  
J. Troy Blackburn ◽  
Darin A. Padua ◽  
Kevin M. Guskiewicz
Keyword(s):  
Muscle Spindle ◽  
Stretch Reflex ◽  
Motor Response ◽  
Triceps Surae ◽  
Joint Stability ◽  
High Stiffness ◽  
Reflex Latency ◽  
Low Stiffness ◽  
Spinal Stretch Reflex ◽  
Musculotendinous Stiffness

Abstract Context: Greater musculotendinous stiffness may enhance spinal stretch reflex sensitivity by improving mechanical coupling of the muscle spindle and the stretch stimulus. This heightened sensitivity would correspond with a shorter latency and higher-amplitude reflex response, potentially enhancing joint stability. Objective: To compare spinal stretch reflex latency and amplitude across groups that differed in musculotendinous stiffness. Design: Static group comparisons. Setting: Research laboratory. Patients or Other Participants: Forty physically active individuals (20 men, 20 women). Intervention(s): We verified a sex difference in musculotendinous stiffness and compared spinal stretch reflex latency and amplitude in high-stiffness (men) and low-stiffness (women) groups. We also evaluated relationships between musculotendinous stiffness and spinal stretch reflex latency and amplitude, respectively. Main Outcome Measure(s): Triceps surae musculotendinous stiffness and soleus spinal stretch reflex latency and amplitude were assessed at 30% of a maximal voluntary isometric plantar-flexion contraction. Results: The high-stiffness group demonstrated significantly greater stiffness (137.41 ± 26.99 N/cm) than the low-stiffness group did (91.06 ± 20.10 N/cm). However, reflex latency (high stiffness = 50.11 ± 2.07 milliseconds, low stiffness = 48.26 ± 2.40 milliseconds) and amplitude (high stiffness = 0.28% ± 0.12% maximum motor response, low stiffness = 0.31% ± 0.16% maximum motor response) did not differ significantly across stiffness groups. Neither reflex latency (r = .053, P = .746) nor amplitude (r = .073, P = .653) was related significantly to musculotendinous stiffness. Conclusions: A moderate level of pretension (eg, 30%) likely eliminates series elastic slack; thus, a greater change in force per unit-of-length change (ie, heightened stiffness) would have minimal effects on coupling of the muscle spindle and the stretch stimulus and, therefore, on spinal stretch reflex sensitivity. It appears unlikely that differences in musculotendinous stiffness influenced spinal stretch reflex sensitivity when initiated from a moderate level of pretension. Consequently, differences in musculotendinous stiffness did not appear to influence dynamic joint stability with respect to reflexive neuromuscular control.

Influences of experimental factors on spinal stretch reflex latency and amplitude in the human triceps surae

2006 ◽  
Vol 16 (1) ◽  
pp. 42-50 ◽  
Author(s):  
J. Troy Blackburn ◽  
Richard G. Mynark ◽  
Darin A. Padua ◽  
Kevin M. Guskiewicz
Keyword(s):  
Stretch Reflex ◽  
Triceps Surae ◽  
Reflex Latency ◽  
Human Triceps Surae ◽  
Spinal Stretch Reflex

scholarly journals Changes in stretch reflexes and muscle stiffness with age in prepubescent children

2007 ◽  
Vol 102 (6) ◽  
pp. 2352-2360 ◽  
Author(s):  
Jean-Francois Grosset ◽  
Isabelle Mora ◽  
Daniel Lambertz ◽  
Chantal Pérot
Keyword(s):  
Stretch Reflex ◽  
Motor Response ◽  
Muscle Stiffness ◽  
Triceps Surae ◽  
Reflex Response ◽  
Passive Stiffness ◽  
Hoffmann Reflex ◽  
Stretch Reflexes ◽  
T Reflex ◽  
Tendon Jerk

Musculo-articular stiffness of the triceps surae (TS) increases with age in prepubescent children, under both passive and active conditions. This study investigates whether these changes in muscle stiffness influence the amplitude of the reflex response to muscle stretch. TS stiffness and reflex activities were measured in 46 children (7–11 yr old) and in 9 adults. The TS Hoffmann reflex (H reflex) and T reflex (tendon jerk) in response to taping the Achilles tendon were evaluated at rest and normalized to the maximal motor response (Mmax). Sinusoidal perturbations of passive or activated muscles were used to evoke stretch reflexes and to measure passive and active musculoarticular stiffness. The children's Hmax-to-Mmax ratio did not change with age and did not differ from adult values. The T-to-Mmax ratio increased with age but remained significantly lower than in adults. Passive stiffness also increased with age and was correlated with the T-to-Mmax ratio. Similarly, the children's stretch reflex and active musculoarticular stiffness were significantly correlated and increased with age. We conclude that prepubescent children have smaller T reflexes and stretch reflexes than adults, and the lower musculoarticular stiffness is mainly responsible for these smaller reflexes, as indicated by the parallel increases in reflex and stiffness.

Influence of long-term spaceflight on neuromechanical properties of muscles in humans

2003 ◽  
Vol 94 (2) ◽  
pp. 490-498 ◽  
Author(s):  
Daniel Lambertz ◽  
Francis Goubel ◽  
Rustem Kaspranski ◽  
Chantal Pérot
Keyword(s):  
Elastic Properties ◽  
Stretch Reflex ◽  
Triceps Surae ◽  
Individual Data ◽  
Stretch Reflexes ◽  
Reflex Excitability ◽  
Voluntary Contractions ◽  
Musculotendinous Stiffness

Reflex and elastic properties of the triceps surae (TS) were measured on 12 male cosmonauts 28–40 days before a 3- to 6-mo spaceflight, 2 or 3 days after return (R+2/+3) and a few days later (R+5/+6). H reflexes to electrical stimulations and T reflexes to tendon taps gave the reflex excitability at rest. Under voluntary contractions, reflex excitability was assessed by the stretch reflex, elicited by sinusoidal length perturbations. Stiffness measurements concerned the musculoarticular system in passive conditions and the musculotendinous complex in active conditions. Results indicated 1) no changes ( P > 0.05) in H reflexes, whatever the day of test, and 2) increase in T reflexes ( P < 0.05) by 57%, despite a decrease ( P < 0.05) in musculoarticular stiffness (11%) on R+2/+3. T reflexes decreased ( P < 0.05) between R+2/+3 and R+5/+6 (−21%); 3) increase in stretch reflexes ( P< 0.05) on R+2/+3 by 31%, whereas it decreased ( P < 0.05) between R+2/+3 and R+5/+6 (−29%). Musculotendinous stiffness was increased ( P < 0.05) whatever the day of test (25%). Links between changes in reflex and stiffness were also studied by considering individual data. At R+2/+3, correlated changes between T reflexes and musculoarticular stiffness suggested that, besides central adaptive phenomena, musculoarticular structures took part in the reflex adaptation. This mechanical contribution was confirmed when data collected at R+2/+3 and R+5/+6 were used because correlations between changes in stretch reflexes and musculotendinous stiffness were improved. In conclusion, the present study shows that peripheral influences take part in reflex changes in gravitational unloaded muscles, but can only be revealed when central influences are reduced.

Effects of postural threat on spinal stretch reflexes: evidence for increased muscle spindle sensitivity?

2013 ◽  
Vol 110 (4) ◽  
pp. 899-906 ◽  
Author(s):  
Brian C. Horslen ◽  
Chantelle D. Murnaghan ◽  
J. Timothy Inglis ◽  
Romeo Chua ◽  
Mark G. Carpenter
Keyword(s):  
Muscle Spindle ◽  
Stretch Reflex ◽  
Sensory Information ◽  
Muscle Spindles ◽  
Support Surface ◽  
Stretch Reflexes ◽  
Postural Threat ◽  
Elevated Surface ◽  
Spinal Stretch Reflex ◽  
T Reflex

Standing balance is often threatened in everyday life. These threats typically involve scenarios in which either the likelihood or the consequence of falling is higher than normal. When cats are placed in these scenarios they respond by increasing the sensitivity of muscle spindles imbedded in the leg muscles, presumably to increase balance-relevant afferent information available to the nervous system. At present, it is unknown whether humans also respond to such postural threats by altering muscle spindle sensitivity. Here we present two studies that probed the effects of postural threat on spinal stretch reflexes. In study 1 we manipulated the threat associated with an increased consequence of a fall by having subjects stand at the edge of an elevated surface (3.2 m). In study 2 we manipulated the threat by increasing the likelihood of a fall by occasionally tilting the support surface on which subjects stood. In both scenarios we used Hoffmann (H) and tendon stretch (T) reflexes to probe the spinal stretch reflex circuit of the soleus muscle. We observed increased T-reflex amplitudes and unchanged H-reflex amplitudes in both threat scenarios. These results suggest that the synaptic state of the spinal stretch reflex is unaffected by postural threat and that therefore the muscle spindles activated in the T-reflexes must be more sensitive in the threatening conditions. We propose that this increase in sensitivity may function to satisfy the conflicting needs to restrict movement with threat, while maintaining a certain amount of sensory information related to postural control.

scholarly journals Main thoracic curve adolescent idiopathic scoliosis: association of higher rod stiffness and concave-side pedicle screw density with improvement in sagittal thoracic kyphosis restoration

2015 ◽  
Vol 22 (3) ◽  
pp. 259-266 ◽  
Author(s):  
Hui Liu ◽  
Zemin Li ◽  
Sibei Li ◽  
Kuibo Zhang ◽  
Hao Yang ◽  
...  
Keyword(s):  
High Density ◽  
Thoracic Curve ◽  
Screw Placement ◽  
Major Curve ◽  
High Stiffness ◽  
Main Thoracic ◽  
Group A ◽  
Screw Density ◽  
Low Stiffness ◽  
Group D

OBJECT The aim of this study was to evaluate the effects of rod stiffness and implant density on coronal and sagittal plane correction in patients with main thoracic curve adolescent idiopathic scoliosis (AIS). METHODS The authors conducted a retrospective study of 77 consecutive cases involving 56 female and 21 male patients with Lenke Type 1 main thoracic curve AIS who underwent single-stage posterior correction and instrumented spinal fusion with pedicle screw fixation between July 2009 and July 2012. The patients' mean age at surgery was 15.79 ± 3.21 years. All patients had at least 1 year of follow-up. Radiological parameters in the coronal and sagittal planes, including Cobb angle of the major curve, side-bending Cobb angle of the major curve, thoracic kyphosis (TK), correction rates, and screw density, were measured and analyzed. Screw densities (calculated as number of screws per fusion segment × 2) of < 0.60 and ≥ 0.60 were defined as low and high density, respectively. Titanium rods of 5.5 mm and 6.35 mm diameter were defined as low and high stiffness, respectively. Patients were divided into 4 groups based on the type of rod and density of screw placement that had been used: Group A, low-stiffness rod with low density of screw placement; Group B, low-stiffness rod with high density of screw placement; Group C, high-stiffness rod with low density of screw placement; Group D, high-stiffness rod with high density of screw placement. RESULTS The mean coronal correction rate of the major curve, for all 77 patients, was (81.45% ± 7.51%), and no significant difference was found among the 4 groups (p > 0.05). Regarding sagittal plane correction, Group A showed a significant decrease in TK after surgery (p < 0.05), while Group D showed a significant increase (p < 0.05); Group B and C showed no significant postoperative changes in TK (p > 0.05). The TK restoration rate was highest in Group D and lowest in Group A (A, −39.32% ± 7.65%; B, −0.37% ± 8.25%; C, −4.04% ± 6.77%; D, 37.59% ± 8.53%). Screw density on the concave side was significantly higher than that on the convex side in all the groups (p < 0.05). CONCLUSIONS For flexible main thoracic curve AIS, both rods with high stiffness and those with low stiffness combined with high or low screw density could provide effective correction in the coronal plane; rods with high stiffness along with high screw density on the concave side could provide better outcome with respect to sagittal TK restoration.

scholarly journals Deal Breaker: Semaphorin and Specificity in the Spinal Stretch Reflex Circuit

Neuron ◽  
2009 ◽  
Vol 63 (1) ◽  
pp. 8-11 ◽  
Author(s):  
Géraldine S. Maro ◽  
Kang Shen ◽  
Hwai-Jong Cheng
Keyword(s):  
Stretch Reflex ◽  
Spinal Stretch Reflex

scholarly journals Acquisition of a simple motor skill: task-dependent adaptation and long-term changes in the human soleus stretch reflex

2019 ◽  
Vol 122 (1) ◽  
pp. 435-446 ◽  
Author(s):  
N. Mrachacz-Kersting ◽  
U. G. Kersting ◽  
P. de Brito Silva ◽  
Y. Makihara ◽  
L. Arendt-Nielsen ◽  
...  
Keyword(s):  
Operant Conditioning ◽  
Stretch Reflex ◽  
Conditioning Session ◽  
H Reflex ◽  
Reflex Change ◽  
Reflex Pathways ◽  
Term Change ◽  
Neurologically Normal ◽  
Spinal Stretch Reflex

Changing the H reflex through operant conditioning leads to CNS multisite plasticity and can affect previously learned skills. To further understand the mechanisms of this plasticity, we operantly conditioned the initial component (M1) of the soleus stretch reflex. Unlike the H reflex, the stretch reflex is affected by fusimotor control, comprises several bursts of activity resulting from temporally dispersed afferent inputs, and may activate spinal motoneurons via several different spinal and supraspinal pathways. Neurologically normal participants completed 6 baseline sessions and 24 operant conditioning sessions in which they were encouraged to increase (M1up) or decrease (M1down) M1 size. Five of eight M1up participants significantly increased M1; the final M1 size of those five participants was 143 ± 15% (mean ± SE) of the baseline value. All eight M1down participants significantly decreased M1; their final M1 size was 62 ± 6% of baseline. Similar to the previous H-reflex conditioning studies, conditioned reflex change consisted of within-session task-dependent adaptation and across-session long-term change. Task-dependent adaptation was evident in conditioning session 1 with M1up and by session 4 with M1down. Long-term change was evident by session 10 with M1up and by session 16 with M1down. Task-dependent adaptation was greater with M1up than with the previous H-reflex upconditioning. This may reflect adaptive changes in muscle spindle sensitivity, which affects the stretch reflex but not the H reflex. Because the stretch reflex is related to motor function more directly than the H reflex, M1 conditioning may provide a valuable tool for exploring the functional impact of reflex conditioning and its potential therapeutic applications. NEW & NOTEWORTHY Since the activity of stretch reflex pathways contributes to locomotion, changing it through training may improve locomotor rehabilitation in people with CNS disorders. Here we show for the first time that people can change the size of the soleus spinal stretch reflex through operant conditioning. Conditioned stretch reflex change is the sum of task-dependent adaptation and long-term change, consistent with H-reflex conditioning yet different from it in the composition and amount of the two components.

Response to sudden torques about ankle in man. II. Postmyotatic reactions

1980 ◽  
Vol 43 (1) ◽  
pp. 86-101 ◽  
Author(s):  
G. L. Gottlieb ◽  
G. C. Agarwal
Keyword(s):  
Tibialis Anterior ◽  
Stretch Reflex ◽  
Reaction Times ◽  
Tonic Contraction ◽  
Triceps Surae ◽  
Afferent Pathways ◽  
Triggered Reaction ◽  
Applied Torque ◽  
Significant Difference ◽  
The Subject

1. Torques were applied to dorsiflex or plantarflex the ankle joint of normal human subjects who were instructed to react to them in various ways. Myoelectric and mechanical responses were recorded and analyzed. 2. Myoelectric responses in triceps surae or tibialis anterior with times of onset between 100 and 200 ms are conditional on the instruction to the subject and not the direction of the applied torque. These responses are termed postmyotatic responses. 3. The latency of the postmyotatic response is the same in both triceps surae and tibialis anterior. It is not dependent on the direction of the applied torque and consequently is not a "stretch reflex," but a triggered reaction. 4. When the subject is sitting relaxed and instructed to resist the applied torque, the magnitude of the postmyotatic response is highly and linearly correlated with the rate of ankle rotation produced by the disturbing torque. 5. Tonic contraction of the muscles prior to the onset of a stretching torque has only a slight effect on the magnitude of the postmyotatic response and usually reduces it. Prior tonic contraction of the antagonist also has a modest effect in reducing the response. 6. Instructing the subject to resist a torque as quickly and strongly as possible increases the magnitude of the postmyotatic response but has little effect on its linear functional relationship to the magnitude of the mechanical stimulus. 7. The postmyotatic response, although voluntary and kinesthetically triggered, is not completely equivalent to a visually triggered voluntary reaction because under experimental situations designed to measure simple reaction times and choice reaction times of the postmyotatic response, no significant difference is found between the two conditions. 8. It is suggested that the peripheral afferent pathways of the stretch reflex play a dual role in determining postmyotatic responses. First, they provide to supraspinal centers one early proprioceptive signal about limb perturbation that can trigger a previously selected mode of response. Second, they modulate that response by convergence, at the segmental level, of peripheral afferent signals with the descending command signals.

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