Muscle length: A new feature to investigate neural control of lengthening contractions

2020 ◽  
Vol 105 (6) ◽  
pp. 930-931
Author(s):  
Marc Jubeau ◽  
Valentin Doguet
Keyword(s):  
Neural Control ◽  
Muscle Length ◽  
Lengthening Contractions ◽  
New Feature

Attenuation of force deficit after lengthening contractions in soleus muscle from trained rats

2000 ◽  
Vol 88 (4) ◽  
pp. 1254-1258 ◽  
Author(s):  
Luc E. Gosselin
Keyword(s):  
Exercise Training ◽  
Exercise Intensity ◽  
Muscle Length ◽  
Training Group ◽  
Treadmill Running ◽  
Similar Degree ◽  
Lengthening Contractions ◽  
Lengthening Contraction ◽  
Old Rats

The purposes of this study were 1) to determine the extent to which endurance training reduces the functional deficit induced by lengthening contractions in the soleus (Sol) muscle and 2) to determine whether young and old rats training at a comparable relative exercise intensity would demonstrate a similar protective effect from lengthening-contraction-induced injury. Young (3-mo-old) and old (23-mo-old) male Fischer 344 rats were randomly assigned to either a control or exercise training group [young control (YC), old control (OC), young trained (YT), old trained (OT)]. Exercise training consisted of 10 wk of treadmill running (15% grade, 45 min/day, and 5 days/wk) such that by the end of training the young and old rats were exercising at 27 and 15 m/min, respectively. After training, contractile properties of the Sol muscle were measured in vitro at 26°C. The percent decrease in maximal isometric specific force (Po) was determined after a series of 20 lengthening contractions (20% strain from optimal muscle length, 1 contraction every 5 s). After the lengthening-contraction protocol, Sol muscle Po was decreased by ∼26% (19.6 vs. 14.6 N/cm2) and 28% (14.8 vs. 9.6 N/cm2) in the YC and OC rats, respectively. After exercise training, the reduction in Po was significantly ( P < 0.05) attenuated to a similar degree (∼13%) in both YT rats (18.7 vs. 16.2 N/cm2) and OT rats (15.8 vs. 13.7 N/cm2). It is concluded that exercise training attenuates the force deficit after repeated lengthening contractions to a comparable extent in young and old rats training at a similar exercise intensity.

Differential costal and crural diaphragm compensation for posture changes

1985 ◽  
Vol 58 (6) ◽  
pp. 1895-1900 ◽  
Author(s):  
E. van Lunteren ◽  
M. A. Haxhiu ◽  
N. S. Cherniack ◽  
M. D. Goldman
Keyword(s):  
Neural Control ◽  
Muscle Length ◽  
Control Mechanisms ◽  
Fine Wire ◽  
Supine Posture ◽  
Crural Diaphragm ◽  
Resting Muscle

The electromyographic (EMG) activities of the costal and crural diaphragm were recorded from bipolar fine-wire electrodes placed in the costal fibers adjacent to the central tendon and in the anterior portions of the crural fibers in 12 anesthetized cats. The EMG activities of costal and crural recordings were compared during posture changes from supine to head up and during progressive hyperoxic hypercapnia in both positions. The activity of both portions of the diaphragm was greater in the head up compared with supine posture at all levels of CO2; and increases in crural activity were greater than those in costal activity both as a result of changes in posture and with increasing CO2 stimuli. These results are consistent with the concept that diaphragm activation is modulated in response to changes in resting muscle length, and further, that neural control mechanisms allow separate regulation of costal and crural diaphragm activation.

scholarly journals Age-related changes in leg proprioception: implications for postural control

2019 ◽  
Vol 122 (2) ◽  
pp. 525-538 ◽  
Author(s):  
Mélanie Henry ◽  
Stéphane Baudry
Keyword(s):  
Postural Control ◽  
Neural Control ◽  
Body Position ◽  
Muscle Length ◽  
Functional Independence ◽  
Body Sway ◽  
Neural Pathways ◽  
Age Related ◽  
Proprioceptive Signal ◽  
Upright Standing

In addition to being a prerequisite for many activities of daily living, the ability to maintain steady upright standing is a relevant model to study sensorimotor integrative function. Upright standing requires managing multimodal sensory inputs to produce finely tuned motor output that can be adjusted to accommodate changes in standing conditions and environment. The sensory information used for postural control mainly arises from the vestibular system of the inner ear, vision, and proprioception. Proprioception (sense of body position and movement) encompasses signals from mechanoreceptors (proprioceptors) located in muscles, tendons, and joint capsules. There is general agreement that proprioception signals from leg muscles provide the primary source of information for postural control. This is because of their exquisite sensitivity to detect body sway during unperturbed upright standing that mainly results from variations in leg muscle length induced by rotations around the ankle joint. However, aging is associated with alterations of muscle spindles and their neural pathways, which induce a decrease in the sensitivity, acuity, and integration of the proprioceptive signal. These alterations promote changes in postural control that reduce its efficiency and thereby may have deleterious consequences for the functional independence of an individual. This narrative review provides an overview of how aging alters the proprioceptive signal from the legs and presents compelling evidence that these changes modify the neural control of upright standing.

Excitability at the Motoneuron Pool and Motor Cortex Is Specifically Modulated in Lengthening Compared to Isometric Contractions

2009 ◽  
Vol 101 (4) ◽  
pp. 2030-2040 ◽  
Author(s):  
M. Gruber ◽  
V. Linnamo ◽  
V. Strojnik ◽  
T. Rantalainen ◽  
J. Avela
Keyword(s):  
Motor Cortex ◽  
Neural Control ◽  
Biceps Brachii ◽  
Cortical Excitability ◽  
Motor Evoked Potentials ◽  
Isometric Contractions ◽  
Spinal Level ◽  
Lengthening Contractions ◽  
Control Of Muscle Contraction ◽  
Isometric Muscle

Neural control of muscle contraction seems to be unique during muscle lengthening. The present study aimed to determine the specific sites of modulatory control for lengthening compared with isometric contractions. We used stimulation of the motor cortex and corticospinal tract to observe changes at the spinal and cortical levels. Motor-evoked potentials (MEPs) and cervicomedullary MEPs (CMEPs) were evoked in biceps brachii and brachioradialis during maximal and submaximal lengthening and isometric contractions at the same elbow angle. Sizes of CMEPs and MEPs were lower in lengthening contractions for both muscles (by ∼28 and ∼16%, respectively; P < 0.01), but MEP-to-CMEP ratios increased (by ∼21%; P < 0.05). These results indicate reduced excitability at the spinal level but enhanced motor cortical excitability for lengthening compared with isometric muscle contractions.

Ia-afferent input to motoneurons during shortening and lengthening muscle contractions in humans

2007 ◽  
Vol 102 (1) ◽  
pp. 144-148 ◽  
Author(s):  
Nicolas T. Petersen ◽  
Jane E. Butler ◽  
Mark G. Carpenter ◽  
Andrew G. Cresswell
Keyword(s):  
Motor Unit ◽  
Muscle Length ◽  
Motor Units ◽  
Common Peroneal Nerve ◽  
Electrical Stimulus ◽  
Afferent Input ◽  
Muscle Contractions ◽  
Afferent Feedback ◽  
Lengthening Contractions ◽  
Active Motor

The central nervous system employs different strategies to execute specific motor tasks. Because afferent feedback during shortening and lengthening muscle contractions differs, the neural strategy underlying these tasks may be quite distinct. Cortical drive may be adjusted or afferent input regulated. The exact mechanisms are not clear. Here, we examine the control of synaptic transmission across the Ia synapse during shortening and lengthening muscle contractions. Subjects were instructed to maintain isolated activity in a single tibialis anterior (TA) motor unit while muscle length was varied from flexion to extension and back. At a fixed interval after a firing of the active motor unit, a single electrical stimulus was applied to the common peroneal nerve to activate Ia afferents from the TA muscle. We investigated the stimulus-induced change in firing probability of 19 individual low-threshold TA motor units during shortening and lengthening contractions. Any change in firing probability depends on both pre- and postsynaptic mechanisms. In this experiment, motoneuron firing rate was similar during both contraction types. There was no difference in the firing probability between shortening and lengthening contractions (0.23 ± 0.03 and 0.20 ± 0.02, respectively). We suggest that there is no contraction type-specific control of Ia input to the motoneurons during shortening and lengthening muscle contractions. Cortical adjustments may have occurred.

scholarly journals Neural control of lengthening contractions

2016 ◽  
Vol 219 (2) ◽  
pp. 197-204 ◽  
Author(s):  
Jacques Duchateau ◽  
Roger M. Enoka
Keyword(s):  
Neural Control ◽  
Lengthening Contractions
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