Different modulation pattern of spinal stretch reflex excitability in highly trained endurance runners

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

Journal of Neurophysiology ◽

10.1152/jn.00211.2019 ◽

2019 ◽

Vol 122 (1) ◽

pp. 435-446 ◽

Cited By ~ 2

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.

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Aging effects on posture-related modulation of stretch reflex excitability in the ankle muscles in humans

Journal of Electromyography and Kinesiology ◽

10.1016/j.jelekin.2011.10.009 ◽

2012 ◽

Vol 22 (1) ◽

pp. 31-36 ◽

Cited By ~ 4

Author(s):

Hiroki Obata ◽

Noritaka Kawashima ◽

Tatsuyuki Ohtsuki ◽

Kimitaka Nakazawa

Keyword(s):

Stretch Reflex ◽

Aging Effects ◽

Reflex Excitability ◽

Ankle Muscles

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Reduced day-to-day variation accompanies adaptive plasticity in the primate spinal stretch reflex

Neuroscience Letters ◽

10.1016/s0304-3940(85)80073-2 ◽

1985 ◽

Vol 54 (2-3) ◽

pp. 165-171 ◽

Cited By ~ 5

Author(s):

Jonathan R. Wolpaw ◽

Julie A. O’Keefe ◽

Victor A. Kieffer ◽

Michael G. Sanders

Keyword(s):

Stretch Reflex ◽

Adaptive Plasticity ◽

Spinal Stretch Reflex

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Enhanced Stretch Reflex Excitability of the Soleus Muscle in Persons With Incomplete Rather Than Complete Chronic Spinal Cord Injury

Archives of Physical Medicine and Rehabilitation ◽

10.1016/j.apmr.2005.08.122 ◽

2006 ◽

Vol 87 (1) ◽

pp. 71-75 ◽

Cited By ~ 31

Author(s):

Kimitaka Nakazawa ◽

Noritaka Kawashima ◽

Masami Akai

Keyword(s):

Spinal Cord ◽

Spinal Cord Injury ◽

Soleus Muscle ◽

Stretch Reflex ◽

Chronic Spinal Cord Injury ◽

Reflex Excitability ◽

Cord Injury

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Adaptive plasticity in primate spinal stretch reflex: persistence

Journal of Neurophysiology ◽

10.1152/jn.1986.55.2.272 ◽

1986 ◽

Vol 55 (2) ◽

pp. 272-279 ◽

Cited By ~ 19

Author(s):

J. R. Wolpaw ◽

J. A. O'Keefe ◽

P. A. Noonan ◽

M. G. Sanders

Keyword(s):

Data Collection ◽

Stretch Reflex ◽

Control Mode ◽

Adaptive Plasticity ◽

Amplitude Change ◽

Absolute Value ◽

Amplitude Mode ◽

Spinal Stretch Reflex ◽

Random Times ◽

Emg Electrodes

Monkeys can gradually change the amplitude of the wholly segmental, largely monosynaptic, spinal stretch reflex (SSR) when confronted by a task requiring such change (15-19). Change develops over months and may reverse and redevelop at similarly slow rates. We investigated the persistence of SSR amplitude change over nonperformance periods of up to 38 days. Eight animals with chronic EMG electrodes learned to maintain elbow angle and a given level of biceps background EMG against constant extension torque. At random times, a brief additional extension torque pulse elicited the biceps SSR. In the control mode, reward always followed. Under the SSR increase or SSR decrease mode, reward occurred only if the absolute value of biceps EMG in the SSR interval was above or below a set value. Animals completed 3,000-6,000 trials/day over data-collection periods of 2-17 mo. Animals worked first under the control mode for up to 60 days and then under the SSR increase or SSR decrease mode for up to 274 days. Mode was switched once or twice more (SSR increase to SSR decrease or vice versa) over subsequent months. Animals responded to each SSR increase or SSR decrease mode exposure with gradual mode-appropriate change in SSR amplitude. Mode exposures were interrupted by gaps in performance of 10-38 days. Gaps produced transient 10- to 15% decreases in SSR amplitude under the control mode. This nonspecific decrease disappeared over the first week of postgap performance. Under the control mode, gaps had no other effects on SSR amplitude.(ABSTRACT TRUNCATED AT 250 WORDS)

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Muscle Stiffness and Spinal Stretch Reflex Sensitivity in the Triceps Surae

Journal of Athletic Training ◽

10.4085/1062-6050-43.1.29 ◽

2008 ◽

Vol 43 (1) ◽

pp. 29-36 ◽

Cited By ~ 15

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.

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