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 contraction intensity on muscle fascicle and stretch reflex behavior in the human triceps surae

2008 ◽  
Vol 105 (1) ◽  
pp. 226-232 ◽  
Author(s):  
Neil J. Cronin ◽  
Jussi Peltonen ◽  
Masaki Ishikawa ◽  
Paavo V. Komi ◽  
Janne Avela ◽  
...  
Keyword(s):  
Stretch Reflex ◽  
Force Production ◽  
Voluntary Contraction ◽  
Short Latency ◽  
Afferent Feedback ◽  
Triceps Surae ◽  
Medial Gastrocnemius ◽  
Stretch Reflexes ◽  
Muscle Fascicle ◽  
Human Triceps Surae

The aims of this study were to examine changes in the distribution of a stretch to the muscle fascicles with changes in contraction intensity in the human triceps surae and to relate fascicle stretch responses to short-latency stretch reflex behavior. Thirteen healthy subjects were seated in an ankle ergometer, and dorsiflexion stretches (8°; 250°/s) were applied to the triceps surae at different moment levels (0–100% of maximal voluntary contraction). Surface EMG was recorded in the medial gastrocnemius, soleus, and tibialis anterior muscles, and ultrasound was used to measure medial gastrocnemius and soleus fascicle lengths. At low forces, reflex amplitudes increased despite a lack of change or even a decrease in fascicle stretch velocities. At high forces, lower fascicle stretch velocities coincided with smaller stretch reflexes. The results revealed a decline in fascicle stretch velocity of over 50% between passive conditions and maximal force levels in the major muscles of the triceps surae. This is likely to be an important factor related to the decline in stretch reflex amplitudes at high forces. Because short-latency stretch reflexes contribute to force production and stiffness regulation of human muscle fibers, a reduction in afferent feedback from muscle spindles could decrease the efficacy of human movements involving the triceps surae, particularly where high force production is required.

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.

scholarly journals Altered activation patterns by triceps surae stretch reflex pathways in acute and chronic spinal cord injury

2011 ◽  
Vol 106 (4) ◽  
pp. 1669-1678 ◽  
Author(s):  
Alain Frigon ◽  
Michael D. Johnson ◽  
C. J. Heckman
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Stretch Reflex ◽  
Triceps Surae ◽  
Stretch Reflexes ◽  
Activation Patterns ◽  
Intact State ◽  
Hindlimb Muscles ◽  
Reflex Pathways ◽  
Cord Injury

Spinal reflexes are modified by spinal cord injury (SCI) due the loss of excitatory inputs from supraspinal structures and changes within the spinal cord. The stretch reflex is one of the simplest pathways of the central nervous system and was used presently to evaluate how inputs from primary and secondary muscle spindles interact with spinal circuits before and after spinal transection (i.e., spinalization) in 12 adult decerebrate cats. Seven cats were spinalized and allowed to recover for 1 mo (i.e., chronic spinal state), whereas 5 cats were evaluated before (i.e., intact state) and after acute spinalization (i.e., acute spinal state). Stretch reflexes were evoked by stretching the left triceps surae (TS) muscles. The force evoked by TS muscles was recorded along with the activity of several hindlimb muscles. Stretch reflexes were abolished in the acute spinal state due to an inability to activate TS muscles, such as soleus (Sol) and lateral gastrocnemius (LG). In chronic spinal cats, reflex force had partly recovered but Sol and LG activity remained considerably depressed, despite the fact that injecting clonidine could recruit these muscles during locomotor-like activity. In contrast, other muscles not recruited in the intact state, most notably semitendinosus and sartorius, were strongly activated by stretching TS muscles in chronic spinal cats. Therefore, stretch reflex pathways from TS muscles to multiple hindlimb muscles undergo functional reorganization following spinalization, both acute and chronic. Altered activation patterns by stretch reflex pathways could explain some sensorimotor deficits observed during locomotion and postural corrections after SCI.

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.

Spastic Equinus Foot: Multicenter Study of the Long-term Results of Tibial Neurotomy

Neurosurgery ◽  
2004 ◽  
Vol 55 (5) ◽  
pp. 1130-1137 ◽  
Author(s):  
Kevin Buffenoir ◽  
Thomas Roujeau ◽  
Françoise Lapierre ◽  
Philippe Menei ◽  
Dominique Menegalli-Boggelli ◽  
...  
Keyword(s):  
Prospective Study ◽  
Gait Analysis ◽  
Stretch Reflex ◽  
Primary Objective ◽  
Triceps Surae ◽  
Long Term Results ◽  
Functional Improvement ◽  
Claw Toes ◽  
The Mean

Abstract OBJECTIVE: Tibial neurotomy is a surgical technique widely used for the treatment of spastic equinus foot, but it has rarely been evaluated. The primary objective of this prospective study was to provide an objective quantification of the long-term results of tibial neurotomy. METHODS: This multicenter prospective study was conducted from 1999 to 2003. Fifty-five patients with spastic equinus foot were treated in five neurosurgical centers. Preoperative and postoperative clinical evaluation comprised description of the foot deformity, study of stretch reflexes, evaluation of the repercussions of the deformity, and gait analysis. Selective neurotomy was performed in all patients. RESULTS: No postoperative complications were observed. The mean postoperative follow-up was 10 months. Tibial neurotomy improved the appearance of the foot (equinus and varus deformities, claw toes); the equinus score decreased from 1.54 to 0.273 after the operation. Stretch reflex scores were decreased significantly and for a long term after surgery; the mean triceps surae stretch reflex score decreased from 2.46 to 0.47. The angle of passive dorsiflexion of the ankle increased significantly (from −0.56 degrees to +6.85 degrees). Gait analysis demonstrated a statistically significant increase in the speed of the patient's gait after surgical treatment; the time taken by the patient to walk 10 m at a normal speed in shoes decreased from a mean of 55 seconds to 35.16 seconds. Postoperatively, 92.7% of preoperative objectives had been achieved. CONCLUSION: Tibial neurotomy ensures long-term functional improvement of patients with spastic equinus foot. It provides a lasting response for these patients compared with other, more transient treatments.

Statistical Considerations When Assessing Short Latency Stretch Reflexes in the Human Soleus Muscle

Motor Control ◽  
2015 ◽  
Vol 19 (4) ◽  
pp. 253-270 ◽  
Author(s):  
Asger Roer Pedersen ◽  
Peter William Stubbs ◽  
Jørgen Feldbæk Nielsen
Keyword(s):  
Ankle Joint ◽  
Soleus Muscle ◽  
Stretch Reflex ◽  
Short Latency ◽  
Response Magnitude ◽  
Variance Heterogeneity ◽  
Stretch Reflexes ◽  
Response Characteristics ◽  
Normally Distributed

The aim was to investigate trial-by-trial response characteristics in the short-latency stretch reflex (SSR). Fourteen dorsiflexion stretches were applied to the ankle joint with a precontracted soleus muscle on 2 days. The magnitude and variability of trial-by-trial responses of the SSR were assessed. The SSR was log-normally distributed and variance heterogeneous between subjects. For some subjects, the magnitude and variance differed between days and stretches. As velocity increased, variance heterogeneity tended to decrease and response magnitude increased. The current study demonstrates the need to assess trial-by-trial response characteristics and not averaged curves. Moreover, it provides an analysis of SSR characteristics accounting for log-normally distributed and variance heterogeneous trial-by-trial responses.

Enhanced stretch reflex excitability of the soleus muscle in experienced swimmers

2008 ◽  
Vol 105 (2) ◽  
pp. 199-205 ◽  
Author(s):  
Tetsuya Ogawa ◽  
Gee Hee Kim ◽  
Hirofumi Sekiguchi ◽  
Masami Akai ◽  
Shuji Suzuki ◽  
...  
Keyword(s):  
Soleus Muscle ◽  
Stretch Reflex ◽  
Reflex Excitability

Taurine Enhances Stretch Reflex Excitability

2019 ◽  
pp. 359-365
Author(s):  
Salvatore Rotondo ◽  
Rodina Sadek ◽  
Narmin Mekawy ◽  
Monir Arnos ◽  
Abdeslem El Idrissi
Keyword(s):  
Stretch Reflex ◽  
Reflex Excitability

scholarly journals Stretch Reflex Latencies in Spastic Hemiparetic Subjects are Prolonged After Transcutaneous Electrical Nerve Stimulation

1993 ◽  
Vol 20 (2) ◽  
pp. 97-106 ◽  
Author(s):  
Christina W.Y. Hui-Chan ◽  
Mindy F. Levin
Keyword(s):  
Nerve Stimulation ◽  
Transcutaneous Electrical Nerve Stimulation ◽  
Stretch Reflex ◽  
Time Course ◽  
Dorsal Column ◽  
Electrical Nerve Stimulation ◽  
Reflex Excitability ◽  
Reflex Threshold ◽  
Repetitive Electrical Stimulation

ABSTRACT:Low-intensity repetitive electrical stimulation such as dorsal column and transcutaneous electrical nerve stimulation (TENS) reportedly decreases spasticity and improves voluntary motor control. However, the mechanisms mediating these effects are unclear. Recent findings suggest that spasticity may be characterized more appropriately by a decrease in the stretch reflex threshold than by an increase in gain. Our objectives were: (1) to examine possible changes in stretch reflex excitability following 45 min of TENS, (2) to map out the time course of possible post-stimulation effects via both latency and magnitude (amplitude or area) measurements, and (3) to determine the role of segmental versus non-segmental mechanisms involved in mediating these changes. The effects of 45 min of segmentally and heterosegmentally applied TENS on lower limb reflexes in ten spastic hemiparetic subjects were contrasted with those resulting from placebo stimulation. We found that both segmentally and heterosegmentally applied TENS caused an immediate increase in soleus H reflex latencies that was evident for up to 60 minutes post-stimulation in over 75% of the subjects. Similar increases for up to 60 and 40 minutes post-stimulation was noted for the stretch reflex latencies in 50% and 67% of the subjects respectively for segmental and heterosegmental stimulation. These results suggested that manipulation of segmental and heterosegmental afférents for 45 min may lead to a decrease of the otherwise augmented stretch reflex excitability accompanying hemiparetic spasticity.

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