Quantitative evaluation of electromyogram activity in rat extensor and flexor muscles immobilized at different lengths

Hník, P; Vejsada, R.; Goldspink, David F.; Kasicki, S; Krekule, I

doi:10.1016/0014-4886(85)90067-6

Cited by 73 publications

(41 citation statements)

References 41 publications

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“…Their susceptibility may be related to a marked reduction in the normally high level of neural activation they receive for their role in postural maintenance (Hnik, Vejsada, Goldspink, Kasicki & Krekule, 1985). This hypothesis is supported by the finding that superimposing chronic lowfrequency activation, which mimics the normal discharge of slow motoneurones, prevented the atrophy of rabbit soleus during a 2 week period of immobilization (Cotter & Phillips, 1985).…”

Section: Introductionsupporting

confidence: 61%

Chronic stimulation accelerates functional recovery of immobilized soleus muscles of the rabbit

Cotter¹,

Cameron²,

Barry³

et al. 1991

Experimental Physiology

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SUMMARYUnilateral immobilization of rabbit hindlimbs was carried out for 2 weeks with an ankle angle of 90 deg. This was followed either by natural recovery for a further 2 or 4 weeks, or by chronic electrical stimulation of the soleus nerve during 2 weeks recovery using a low-frequency pattern of activation. Immobilization caused gross degeneration and functional disruption of soleus. Mean fibre area was reduced by 60 % compared with unoperated controls, twitch and tetanic tensions by 90 % and there was speeding of the rising phase of contraction. Natural recovery for 2 weeks had little effect; some regeneration occurred but muscle fibres remained atrophied and immature as indicated by the histochemical expression of both fast and slow myosin. Function continued to be grossly impaired, twitch and tetanic tensions were 66 and 79 % reduced and the time-to-peak twitch tension 31 % faster than controls. Prolonging the natural recovery period to 4 weeks increased muscle fibre area to 60 % of normal, and increased the acquisition of mature staining properties but most functional characteristics remained impaired. Stimulated muscles had normal fibre areas, mature appearance and functional improvements which matched and in most cases exceeded those seen after natural recovery for 4 weeks. Thus chronic low-frequency stimulation of soleus muscles accelerates recovery of structure and function following degenerative immobilization atrophy and may represent an important therapeutic aid in patient rehabilitation.

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Section: Introductionsupporting

confidence: 61%

Chronic stimulation accelerates functional recovery of immobilized soleus muscles of the rabbit

Cotter¹,

Cameron²,

Barry³

et al. 1991

Experimental Physiology

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“…1 Immobilization of a muscle in a shortened or neutral, but not a lengthened, position results in a decrease in neuromuscular activity. 12,15 Since the muscles are active, and the muscles are ''fixed'' at a certain length, forces will be developed when the muscles are activated, and the amount of force will be dependent on the length of the muscle (highest forces when fixed at a lengthened position, at least initially). This confounding factor makes it difficult to interpret the role of neuromuscular activity in the muscle adaptation processes associated with limb immobilization.…”

Section: Discussionmentioning

confidence: 99%

Effects of inactivity on myosin heavy chain composition and size of rat soleus fibers

Roy²,

et al. 1998

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“…This suggested that these muscles were not subjected to atrophy but the growth rate was inhibited by hindlimb suspension. However, atrophy was induced if the ankle joint was maintained in a dorsiflexed position [103,104]. Thus, it is suggested that the length or degree of loading of ankle flexors was also reduced by dorsi-flexion.…”

Section: Tension Developmentmentioning

confidence: 99%

Neuromuscular Adaptation to Microgravity Environment.

Ohira

2000

JJP

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The pattern of muscle activity influences the morphological, metabolic, and contractile properties of skeletal muscles. For example, the metabolic capacity of muscles is affected specifically by the type of exercise training [1][2][3]. Increased activity or over-loading by removing the synergists causes a compensatory hypertrophy [4][5][6][7][8][9][10][11]. Hypertrophy is also induced by the stretching of matured muscles in vivo [12,13] and cultured myotubes and fibroblasts [14][15][16][17]. Exercise-induced metabolic adaptation of muscles is lost when exercise training is stopped [18]. Further, muscle atrophy is induced by denervation [10,19], spinal cord transection [20], joint immobilization [21][22][23], tenotomy [24,25], spaceflight [26][27][28][29], and/or hindlimb suspension [29][30][31][32]. Most of these models are generally presumed to be models of reduced neuromuscular activity. But the level of use may not be the only factor involved in the atrophic process.There is a close association in the physiological, biochemical, and morphological properties between a motoneuron and the muscle fibers it innervates [1]. Studies to support this view are those in which chronic electrical stimulation at low frequency (1-10 Hz) changes the properties of fast-twitch muscles toward those of slow-twitch muscles [33][34][35][36][37][38].Some of the characteristics of muscle fibers are also altered following cross-innervation [39][40][41][42]. Buller et al. [40] suggested that the neural influence on muscle could be due to neurotrophic effect as well as via nerve impulses. Muscular Responses to Gravitational Unloading Morphological propertiesGravitational unloading by exposure to weightlessness [26][27][28][29][43][44][45][46][47] and/or its simulation model, hindlimb suspension [29][30][31][32][48][49][50][51][52][53][54][55][56], causes rapid atrophy in muscles, such as soleus and adductor longus, that are composed predominantly of slow fibers. The cross-sectional areas (CSAs) of both slow-and fasttwitch fibers of rats were less after 14 d of spaceflight and hindlimb suspension than those in the agematched controls [29]. But the degree of atrophy was greater in slow-than fast-twitch fibers [28,29]. Therefore, muscles composed of predominantly slow fibers are more susceptible to atrophy [26,28, 47]. The weights of fast-twitch ankle dorsi-flexors, such as the tibialis anterior (TA) and extensor digitorum longus (EDL), are also generally less after unloading than those of age-matched controls [31, 57]. But these were Japanese Journal of Physiology, 50, 303-314, 2000 Key words: atrophy, fiber-type transformation, contractile properties, neural responses, microgravity.Abstract: Morphological and/or functional characteristics of skeletal muscles have a greater adaptability in response to changes in environmental stimuli. For example, an atrophy associated with a shift of fiber characteristics toward fast-twitch type is a common adaptation of antigravity muscle to a microgravity environment. Neuromuscular responses and ...

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Quantitative evaluation of electromyogram activity in rat extensor and flexor muscles immobilized at different lengths

Cited by 73 publications

References 41 publications

Chronic stimulation accelerates functional recovery of immobilized soleus muscles of the rabbit

Chronic stimulation accelerates functional recovery of immobilized soleus muscles of the rabbit

Effects of inactivity on myosin heavy chain composition and size of rat soleus fibers

Neuromuscular Adaptation to Microgravity Environment.

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