Aging of human segmental oligosynaptic reflexes for control of leg movement

Brooke, J. D.; Singh, Rasnik; Wilson, Molly; Yoon, Peel Sang; McIlroy, William E.

doi:10.1016/0197-4580(89)90009-2

Cited by 20 publications

(10 citation statements)

References 22 publications

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“…For example, Kido et al [81] reported that the soleus H-reflex (a global measurement of spinal excitability) decreased gradually with age. Others have also observed that heteronymous facilitation [82] and oligosynaptic reflexes [83] decrease with age, which provides collective evidence that there is a general decrease in the excitability of spinal reflexes with age. The end result of the morphologic and physiologic adaptations in motor units with aging is alterations in the behavioral discharge properties of motor units.…”

Section: What Are the Potential Neurophysiologic Mechanisms Of Dynapementioning

confidence: 89%

What is dynapenia?

2012

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Dynapenia (pronounced dahy-nuh-pē-nē-a, Greek translation for poverty of strength, power, or force) is the age-associated loss of muscle strength that is not caused by neurologic or muscular diseases. Dynapenia predisposes older adults to an increased risk for functional limitations and mortality. For the past several decades, the literature has largely focused on muscle size as the primary cause of dynapenia; however, recent findings have clearly demonstrated that muscle size plays a relatively minor role. Conversely, subclinical deficits in the structure and function of the nervous system and/or impairments in the intrinsic force-generating properties of skeletal muscle are potential antecedents to dynapenia. This review highlights in the contributors to dynapenia and the etiology and risk factors that predispose individuals to dynapenia. In addition, we address the role of nutrition in the muscular and neurologic systems for the preservation of muscle strength throughout the life span.

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Section: What Are the Potential Neurophysiologic Mechanisms Of Dynapementioning

confidence: 89%

What is dynapenia?

2012

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“…The latency of the H reflex in ECR was longer (age main effect, P Ͻ 0.001) for the old adults (19.0 Ϯ 1.7 ms) than the young adults (16.7 Ϯ 1.7 ms). In the absence of a difference in the height of the subjects (young: 175 Ϯ 8.7 cm; old: 169 Ϯ 10.0 cm; unpaired t-test, P ϭ 0.12), this result suggests a slowing in the nerve conduction velocity (Brooke et al 1989;Dorfman and Bosley 1979), a change synaptic transmission (Sant'Ambrogio et al 1961;Wayner and Emmers 1958), or a combination of the two adaptations. In contrast, no difference was observed in the duration of the H reflex between young (12.4 Ϯ 2.9 ms) and old adults (11.5 Ϯ 2.4 ms; P ϭ 0.16).…”

Section: R E S U L T Smentioning

confidence: 94%

Presynaptic Modulation of Ia Afferents in Young and Old Adults When Performing Force and Position Control

Baudry

Maerz

Enoka

2010

Journal of Neurophysiology

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Baudry S, Maerz AH, Enoka RM. Presynaptic modulation of Ia afferents in young and old adults when performing force and position control. J Neurophysiol 103: 623-631, 2010. First published November 25, 2009 doi:10.1152/jn.00839.2009. The present work investigated presynaptic modulation of Ia afferents in the extensor carpi radialis (ECR) when young and old adults exerted a wrist extension force either to support an inertial load (position control) or to achieve an equivalent constant torque against a rigid restraint (force control) at 5, 10, and 15% of the maximal force. H reflexes were evoked in the ECR by stimulating the radial nerve above the elbow. A conditioning stimulus was applied to the median nerve above the elbow to assess presynaptic inhibition of homonymous Ia afferents (D1 inhibition) or at the wrist (palmar branch) to assess the ongoing presynaptic inhibition of heteronymous Ia afferents that converge onto the ECR motor neuron pool (heteronymous Ia facilitation). The young adults had less D1 inhibition and greater heteronymous Ia facilitation during the position task (79 and 132.1%, respectively) compared with the force task (69.1 and 115.1%, respectively, P Ͻ 0.05). In contrast, the old adults exhibited no difference between the two tasks for either D1 inhibition (ϳ72%) or heteronymous Ia facilitation (ϳ114%). Contraction intensity did not influence the amount of D1 inhibition or heteronymous Ia facilitation for either group of subjects. The amount of antagonist coactivation was similar between tasks for young adults, whereas it was greater in the position task for old adults (P ϭ 0.02). These data indicate that in contrast to young adults, old adults did not modulate presynaptic inhibition of Ia afferents when controlling the position of a compliant load but rather increased coactivation of the antagonist muscle.

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“…Among these individuals, it is estimated that 42% have limitations in performing one or more daily tasks (e.g., walking two to three blocks, transferring from sitting to standing) that are essential for maintaining physical independence [1]. While the causes of physical disability are multifactorial, it is well established that contributing factors associated with age-related physical disability are low levels of voluntary muscle strength and power [2][3][4][5][6][7]. Indeed, over the past several decades, the scientific and medical communities have recognized that both skeletal muscle wasting and weakness are a debilitatingand even life-threatening-condition in older persons [8].…”

Section: Introductionmentioning

confidence: 99%

“…Numerous scientists and clinicians have used the term "muscle quality"-and other related terms such as specific force-to describe the relationship between voluntary muscle strength and muscle size (i.e., decreased muscle quality is indicative of lower muscle strength relative to muscle size) [2,10,[15][16][17][18][19][20][21][22][23][24]. Recent longitudinal data from the Health ABC study of more than 1,600 older adults indicate that knee extensor muscle quality-as defined above-decreases at a staggering rate of ∼2.5%/year (in contrast to muscle crosssectional area decreasing at a rate of ∼1%/year) [10].…”

Section: Introductionmentioning

confidence: 99%

Evolving concepts on the age‐related changes in “muscle quality”

Russ

Gregg-Cornell

Conaway

et al. 2012

J cachexia sarcopenia muscle

123

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The deterioration of skeletal muscle with advancing age has long been anecdotally recognized and has been of scientific interest for more than 150 years. Over the past several decades, the scientific and medical communities have recognized that skeletal muscle dysfunction (e.g., muscle weakness, poor muscle coordination, etc.) is a debilitating and life-threatening condition in the elderly. For example, the age-associated loss of muscle strength is highly associated with both mortality and physical disability. It is well-accepted that voluntary muscle force production is not solely dependent upon muscle size, but rather results from a combination of neurologic and skeletal muscle factors, and that biologic properties of both of these systems are altered with aging. Accordingly, numerous scientists and clinicians have used the term “muscle quality” to describe the relationship between voluntary muscle strength and muscle size. In this review article, we discuss the age-associated changes in the neuromuscular system—starting at the level of the brain and proceeding down to the subcellular level of individual muscle fibers—that are potentially influential in the etiology of dynapenia (age-related loss of muscle strength and power).

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Aging of human segmental oligosynaptic reflexes for control of leg movement

Cited by 20 publications

References 22 publications

What is dynapenia?

What is dynapenia?

Presynaptic Modulation of Ia Afferents in Young and Old Adults When Performing Force and Position Control

Evolving concepts on the age‐related changes in “muscle quality”

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