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PubMed1992

The influence of handedness on the distribution of muscular weakness of the arm in facioscapulohumeral muscular dystrophy.

The strength of 10 muscle groups in both arms was measured using hand-held myometry to determine the influence of handedness on left-right differences of muscle strength in facioscapulohumeral muscular dystrophy (FSHD). Two groups of subjects were studied: 24 healthy volunteers (19 right-handed), and 53 patients (42 right-handed) with autosomal dominant FSHD. An opposite left-right difference of strength of shoulder and arm muscles was found: right-handed volunteers were stronger on the right side, right-handed patients were stronger on the left side. This opposite left-right difference was statistically significant for the supraspinatus muscle, the wrist extensors and the shoulder internal rotators. The number of left-handed subjects was too small for statistical analysis. The relation between handedness and increased muscle weakness in right-handed FSHD patients suggests that mechanical factors may play a distinct role in the progression of muscle weakness in FSHD.

Adolescent↗

PubMed2005

A Caenorhabditis elegans model of the myosin heavy chain IIa E706K [corrected] mutation.

Mutations in myosin heavy chain (MyHC) genes recently have been shown to be associated with various forms of congenital myopathies: myosin myopathies. The MyHC IIa E706K mutation is associated with congenital joint contractures, early-onset muscle weakness, and progressive course with moderate to severe muscle weakness later in life. To study the pathogenicity of this MyHC mutation, we investigated the effect of the corresponding mutation (E710K) in the major MyHC isoform (MyHC B) of the body wall muscle of the nematode Caenorhabditis elegans. Worms with null mutations in the MyHC B gene (unc-54) are severely paralyzed and depleted of thick filaments in the body wall muscle sarcomeres. unc-54 null mutants with extrachromosomal arrays of a gene construct including the entire wild-type unc-54 gene were partially rescued as determined by a motility assay and by morphological analysis of the body wall muscle. Analysis of unc-54 null mutants with extrachromosomal arrays of the unc-54 gene with the E710K mutation were severely paralyzed but showed formation of thick filaments in the body wall muscle. We conclude that the MyHC E706K (E710K in C. elegans) mutation is pathogenic and that the effect is primarily functional rather than structural because thick filaments are formed. The C. elegans model may be useful to study suspected pathogenic mutations in MyHC genes associated with human muscle diseases.

Animals↗

PubMed1997

Na+ channel and acetylcholine receptor changes in muscle at sites distant from burns do not simulate denervation.

Muscle weakness and aberrant responses to neuromuscular relaxants after burn injury are associated with upregulation of acetylcholine receptors (AChRs). Typically, these functional, pharmacological, and biochemical changes occur after denervation, in which transcriptionally mediated qualitative changes in AChRs and Na+ channels and of myogenic regulatory proteins MyoD and myogenin also occur. This study in rats, by an examination of changes in the above-enumerated proteins or their transcripts in the gastrocnemius muscle distant from the burn, verifies whether a denervation-like state exists after burns. Scatchard analysis of [3H]saxitoxin binding revealed no changes in the affinity (K(d)) and total number (B(max)) of Na+ channels between control and burn-injured animals at both 7 and 14 days after injury. The mRNA levels of the immature proteins, SkM2 of the Na+ channels and the gamma-subunits of AChRs, the increase of which is pathognomic of denervation, were assessed by Northern analysis and were unchanged. The transcripts of mature Na+ channels, SkM1, were significantly increased at day 14 after the burn (1.24 +/- 0.10 in burn-injured vs. 1.06 +/- 0.12 in sham animals, arbitrary units, P = 0.006). Although MyoD levels were increased in burn-injured animals at 14 days (0.21 +/- 0.02 vs. 0.15 +/- 0.07 arbitrary units, P = 0.05), myogenin levels were unaltered. The absence of changes in AChR transcripts, including alpha-, delta-, and gamma-subunits, indicates that the upregulation of AChR in burns is not transcriptionally mediated. The unaltered levels of transcripts of myogenin, SkM2 of Na+ channels and gamma-subunit of AChR, confirm that there is no denervation-like prejunctional (nerve-related) component to explain the muscle weakness or the upregulation of AChRs at sites distant from burns.

Animals↗

PubMed2005

Clinical and molecular features of encephalomyopathy due to the A3302G mutation in the mitochondrial tRNA(Leu(UUR)) gene.

BACKGROUND: The mitochondrial DNA mutation A3302G in the tRNA(Leu(UUR)) gene causes respiratory chain complex I deficiency. The main clinical feature appears to be a progressive mitochondrial myopathy with proximal muscle weakness. OBJECTIVE: To report on clinical and molecular features in 4 novel patients with the A3302G mutation. DESIGN: Case reports. PATIENTS: Four patients (3 of whom are from the same family) with a myopathy caused by the A3302G mitochondrial DNA mutation. MAIN OUTCOME MEASURE: Identification of the A3302G mutation by DNA sequencing. RESULTS: All 4 patients had an adult-onset progressive mitochondrial myopathy with proximal muscle weakness, resulting in exercise intolerance. In 2 unrelated patients, upper limb reflexes were absent with preservation of at least some lower limb reflexes. Other features including hearing loss, recurrent headaches, ptosis, progressive external ophthalmoplegia, and depression were present. CONCLUSION: While the dominant clinical features of the A3302G mutation were exercise intolerance and proximal muscle weakness, other features of mitochondrial encephalomyopathies, previously not described for this mutation, were present.

Adult↗

PubMedDate not supplied

Impaired ventilatory capacity after recovery from Guillain-Barré syndrome.

A 48-year-old woman who failed to disclose significant past medical history presented for laparoscopic-assisted vaginal hysterectomy with general anesthesia. After the uneventful induction of anesthesia, her trachea could not be intubated due to an extremely anterior larynx, and she was allowed to awaken. However, she developed upper airway obstruction and displayed marked muscle weakness with inadequate tidal volumes and marginal oxygen saturation. A history of prior Guillain-Barré syndrome was disclosed by the attending gynecologist. The patient's recovery was complicated by the development of postobstructive pulmonary edema and by respiratory insufficiency requiring the use of mask continuous positive airway pressure (CPAP). Despite vigorous diuresis, her respiratory status and muscle weakness did not significantly improve until she received a trial of aminophylline by infusion, after which she was able to be weaned from mask CPAP support. The patient was discharged home and returned 8 weeks later for surgery. She underwent awake fiberoptic intubation, after which general anesthesia was induced and maintained without complication. An aminophylline infusion was used in the perioperative period until the patient was successfully awakened and her trachea extubated. The frequency of residual muscle weakness after apparent full recovery from Guillain-Barré syndrome is discussed, along with the rationale for the use of aminophylline in this patient's clinical management.

Aminophylline↗

PubMed1988

Chronic progressive external ophthalmoplegia. I. A quantitative histochemical study of skeletal muscles.

This study quantitates the major morphological and cytochemical changes in limb muscle biopsies from 37 patients with the syndrome of chronic progressive external ophthalmoplegia (CPEO). The aim was to assess the value of limb muscle biopsy in the diagnosis of this syndrome; to define the myopathological changes and to determine whether there were any specific clinico-pathological correlations. Patients were divided into three clinical groups--11 patients with CPEO with facial and/or limb muscle weakness; 10 with CPEO with facial and/or limb muscle weakness and a positive family history; 16 with CPEO with one or more of the following: pigmentary retinopathy, cerebellar ataxia, pyramidal signs and peripheral neuropathy. The following parameters were measured: the proportions of histochemical fibre types, the muscle fibre areas and the percentage of muscle fibres showing increased oxidative enzyme activity. Pooled results for each of the clinical categories were compared. Statistical analysis of fibre areas and the percentage of fibres with increased oxidative enzyme activity, showed that group 2 differed from the others (p less than 0.05). Patients in group 2 showed the highest incidence of type 1 fibre hypertrophy, type 2A atrophy and the lowest incidence of fibres with increased oxidative activity. Fibre type disproportions occurred in all three groups but the differences were not significant.

Biopsy↗

PubMed1992

Pregnancy and spinal muscular atrophy.

We investigated the course and outcome of pregnancy and its influence on muscle weakness in 12 females with proximal spinal muscular atrophy (SMA) who delivered a total of 17 infants when aged 18-32 years. In 4 females the SMA clearly followed an autosomal recessive mode of inheritance. The disease was autosomal dominantly inherited in 2 patients; the other 6 were sporadic cases. Ages of onset of SMA ranged from 8 months to 29 years; all the females learned to walk, and 10 out of 12 are still ambulatory aged 30-60 years. Pregnancy and delivery were complicated in 10 out of 12 patients by premature labour (4), prolonged labour (3) and delayed postpartum recovery (6). Caesarean section was performed in 3 cases. No deleterious effects on fetal outcome could be detected. Exacerbation of muscle weakness after the second trimester of pregnancy was experienced by 8 females: 5 noticed a persistent deterioration of SMA; in 3 muscle weakness worsened temporarily during pregnancy and was followed by marked improvement in the puerperium. The psychological perceptions, in retrospect, of 10 females concerning their decision to have children were evaluated.

Adult↗

PubMedDate not supplied

High myopia and congenital myopathy with partial pachygyria in cutis laxa syndrome.

PURPOSE: Several types of inborn errors of the O-glycan biosynthesis are known, leading to clinically very distinct phenotypes. Children with O-mannosyl glycan biosynthesis defects commonly present as a severe form of congenital muscular dystrophy with decreased alpha-dystroglycan staining, congenital eye anomalies, and brain migration defects. Alpha-dystroglycan is an O-mannosylated glycoprotein with additional mucin type O-glycans. METHODS: Based on overlapping clinical features with O-mannosyl glycan defects, especially with muscle-eye-brain disease, the authors performed a muscle biopsy in a child with severe congenital hypotonia, high myopia, partial pachygyria, mental retardation, cutis laxa, and an inborn error affecting the biosynthesis of both mucin type O-glycans and N-linked glycans. RESULTS: The histology showed no signs of muscle dystrophy, but a mild myopathy with slight increase in the muscle fiber diameter variability and type I fiber predominance. No significant decrease in the alpha-dystroglycan staining was detected; therefore, in spite of the phenotypic similarities the authors could not confirm the role of abnormal dystroglycan in the etiology of the muscle weakness and the developmental anomalies. CONCLUSIONS: High myopia, muscle weakness, and cortical neuronal migration abnormalities are common in disorders of O-mannosylation and also observed in the authors' patient. However, compared to the severe generalized defect observed in mannosyl glycan defects, in this child the cerebral white matter and cerebellum were spared, and no muscle dystrophy could be confirmed. This is the first description of high myopia in cutis laxa syndrome in combination with congenital disorders of glycosylation.

Abnormalities, Multiple↗

PubMed2005

Retrospective review of the clinical manifestations and outcomes in Puerto Ricans with idiopathic inflammatory myopathies.

BACKGROUND: The idiopathic inflammatory myopathies (IIM) are a heterogeneous group of conditions characterized by chronic inflammation of muscles, resulting in skeletal muscle weakness. Racial differences are apparent in the clinical manifestations and outcome of IIM. No previous studies have been conducted to evaluate the clinical manifestations and outcome of Puerto Ricans with IIM. OBJECTIVE: The objective of this study was to describe demographic characteristics, clinical features, and functional outcome of Puerto Rican patients with IIM. METHODS: Medical records at a university medical center were reviewed retrospectively to collect data regarding demographic factors, initial presentation, diagnostic tests, serologic markers, treatment, and disease course. A Functional Grading Scale was administered to 40 of the patients with IIM to determine their functional status. RESULTS: Fifty patients with IIM were identified. Eight patients had polymyositis (PM), 23 patients had dermatomyositis (DM), 2 patients had DM/PM with coexistent malignancy, 12 patients had juvenile DM, and 5 patients had DM/PM with an associated other rheumatologic disease. At diagnosis, proximal muscle weakness was present in all patients, 15 (30%) had myalgias, 5 (10%) patients had dysphagia, and 87% had elevation of serum muscle enzymes. Visceral involvement was rare. Interstitial fibrosis was identified in only 2 patients (1 juvenile DM and 1 PM). Twenty-six patients (51%) achieved complete remission. The mean score for the Functional Grading Scale was 28.6 (maximum 30). The lowest scores were seen for patients with disease duration of less than 2 years. CONCLUSION: Puerto Ricans with IIM in this survey showed a low presence of visceral involvement, high remission rate, and low mortality.

Adolescent↗

PubMed1999

Sporadic amyotrophic lateral sclerosis of long duration mimicking spinal progressive muscular atrophy: a clinicopathological study.

We report an autopsy case of amyotrophic lateral sclerosis (ALS) clinically diagnosed as spinal progressive muscular atrophy (SPMA). The patient was a Japanese woman without hereditary burden. She developed muscle weakness of the distal part of the left lower extremity at age 42, followed by muscle weakness and atrophy of the right lower extremity and upper extremities. At age 57, she needed transient ventilatory support. Slight weakness in the facial muscles and fasciculation of the tongue appeared at age 60. At age 61, she died of sudden respiratory arrest. During the clinical course, neurological examination revealed neither Babinski signs nor hyperreflexia. The neuropathological examination revealed not only neuronal loss with gliosis in the facial nucleus, hypoglossal nucleus, and anterior horns of the spinal cord, but also loss of Betz cells and degeneration of the pyramidal tracts. Based on these clinicopathological findings and review of literature, we conclude that sporadic ALS mimicking SPMA is present.

Amyotrophic Lateral Sclerosis↗

PubMed1978

Effect of curare on maximum static PV relationships of the respiratory system.

The effect of respiratory muscle weakness on the maximum static pressure-volume (PV) characteristics of the respiratory system was studied in four healthy males infused slowly with d-tubocurarine (dtc). Inspiratory capacity (IC), expiratory reserve volume (ERV), maximum static inspiratory and expiratory mouth pressures at four lung volumes, and handgrip were measured during induction of, and recovery from muscle weakness. The maximum effect of dtc varied among the muscle groups tested; peripheral muscles were most severely affected, expiratory muscles moderately, and inspiratory muscles least affected. At each level of weakness studied, decreases of IC and ERV were proportional to decreases of maximum static mouth pressures. Vital capacity, measured at each level of weakness was much less than values predicted from the static mechanical properties of the respiratory system. Our findings suggest that the marked change in the extremes of lung volume during submaximal neuromuscular blockade (SMNB) is due, in part, to unequal distribution of muscle weakness, reflected by decreased ability to change ribcage dimensions even at modest levels of SMNB.

Abdomen↗

PubMedDate not supplied

Prolonged myasthenic syndrome after one week of muscle relaxants.

A child developed severe, generalized muscle weakness which persisted for 6 weeks, after receiving muscle relaxants for 1 week while requiring ventilator support. Electrodiagnostic studies indicated a presynaptic disorder of the neuromuscular junction which improved with high-frequency stimulation, similar to findings in Lambert-Eaton syndrome. Muscle specimens exhibited neurogenic targetoid fiber atrophy. Ultrastructure of the neuromuscular junction indicated terminal axon degeneration and atrophy with depletion of the secretory vesicles. Most reported patients with post-ventilator paresis have received steroids and muscle relaxants; muscle weakness commonly has been brief and attributed to steroids. We believe that this reversible myasthenic syndrome probably represents neurotoxicity due to high doses of steroidal nondepolarizing blocking agents; however, available data are insufficient to resolve this controversy.

Atrophy↗

PubMed2001

Massive intravenous immunoglobulin treatment in pregnancy complicated by Guillain-Barré Syndrome.

A pregnant woman developed acute demyelinating poly-neuropathy (Guillain-Barré syndrome (GBS)) in the 28th week of gestation (GW) after flu-like infection. Hypertension, liver dysfunction, and a decrease in consciousness level developed at 29GW. Blood chemical analysis revealed increased levels of liver enzymes GOT 247 IU/l and GPT 624 IU/l. Viral serological study showed a positive test for Epstein-Barr virus IgM. Weakness of bilateral facial muscles and limbs, a loss of tendon reflexes, and generalized paresthesia were detected by neurologic examinations. Over the course of 5 days, a massive dose (100g) of intravenous immunoglobulin (MIVIg) was infused in 30GW. An average manual muscle testing score by the Medical Research Council method and peak flow value began to be significantly restored during and after MIVIg infusions. Values of the liver enzymes gradually decreased, and improvement of the muscle weakness and dysbasia was observed. Her pregnancy normally ended in spontaneous vaginal delivery of a healthy infant in 37GW. This is the first report confirming the efficacy of MIVIg, without plasmapheresis, in GBS-complicated pregnancy.

Adult↗

PubMed2002

Polymyositis-like syndrome in hypothyroidism: review of cases reported over the past twenty-five years.

Polymyositis-like syndrome, with proximal muscle weakness and elevation of muscle enzymes, may be a clinical manifestation of hypothyroidism. To define the clinical, biochemical, electromyographic, and pathologic characteristics of patients with this syndrome, we identified and reviewed by MEDLINE all cases reported in the English literature from January 1, 1975 through December 31, 2000. Thirty-two cases were considered. Fifty-nine percent of the patients were male with a mean age of 54.7 +/- 22.6 years, (+/- 1 standard deviation [SD]). Weakness was described in 100% of patients. Other common clinical manifestations were: delayed tendon reflexes with slow relaxation phase (41%), muscle tenderness (25%), and muscle induration (9%). The mean creatine kinase (CK) was 2164 +/- 1954 U/L (+/- 1 SD) and the mean thyroid-stimulating hormone (TSH) was 114.8 +/- 85.6 mIU/L (+/- 1 SD). Fifty percent of patients had electromyography; half of the studies were normal while the other half showed nonspecific myopathic changes. Biopsies were performed in 80% of the patients. The most common findings were type II fiber atrophy, type I fiber hypertrophy, central nuclei disposition, necrosis, increased percentage of type I fibers, and decreased percentage of type II fibers, inflammatory infiltrate and the presence of core-like structures. The characteristics of polymyositis-like syndrome in hypothyroidism did not differ from those of nonspecific hypothyroid myopathy. Clinical judgment alone may not be sufficient to suspect and detect these patients. Serum TSH levels should be routinely determined in all patients with muscle weakness or elevation of creatine kinase.

Adult↗

PubMed2004

Early abnormalities in sciatic nerve function and structure in a rat model of Charcot-Marie-Tooth type 1A disease.

We investigated early peripheral nervous system impairment in PMP22-transgenic rats ("CMT rat"), an established animal model for Charcot-Marie-Tooth disease 1A, at postnatal day 30 (P30), when the clinical phenotype is not yet apparent. Hemizygous CMT1A rats and wildtype littermates were studied by means of behavioral examination, electrophysiology, molecular biology, and light microscopy analysis. Behavioral studies only showed, a mild, but significant, decrease in toe spread 1-5, suggesting a weakness of distal foot muscles in CMT1A rats compared with normal littermates. Nerve conduction studies disclosed a severe slowing in motor conduction velocity, a temporal dispersion and a dramatic decrease of amplitude of motor waves in P30 transgenic animals. Coherently with a demyelinating process, affected nerves showed a significant thinning of myelin. Interestingly, axonal diameter and area were unchanged, but expression of non-phosphorylated neurofilaments was increased in CMT1A rats compared with normal controls. Our results confirm the fidelity of this animal model to human disease. Similarly, in young CMT1A patients, the MCV is significantly reduced and the muscle weakness is confined to distal segments, whereas morphological and morphometrical signs of axonal atrophy are absent. However, the presence of a molecular and functional damage of the axons suggests that this may be the correct moment to start neuroprotective therapies.

Age Factors↗

PubMed1999

Paralysis in the critically ill: intermittent bolus pancuronium compared with continuous infusion.

OBJECTIVES: To compare recovery times from neuromuscular blockade between two groups of critically ill patients in whom pancuronium was administered by continuous infusion or intermittent bolus injection. To compare the mean pancuronium requirements (milligrams per kilogram per hour) and to assess the incidence of prolonged recovery times (>12 hrs) and residual muscle weakness. DESIGN: Prospective, observational cohort. SETTING: Intensive care unit in a university-affiliated hospital. PATIENTS: A total of 30 mechanically ventilated patients who required pharmacologic paralysis. Patients were excluded if they had renal failure (creatinine clearance <30 mL/min), heart rate >130 beats/min, hepatic failure, peripheral nerve disease or myopathy, stroke, spinal cord damage, or myasthenia gravis. INTERVENTIONS: Patients were assigned to receive pancuronium either by continuous infusion (n = 14) or intermittent bolus (n = 16). Depth of paralysis was titrated to maintain one or two responses to Train-of-Four stimulation with an accelerograph and desired clinical goals. Recovery time was defined as time from discontinuation of muscle relaxant until the amplitude of the fourth twitch, measured every 15-30 min using an accelerograph, was 70% the amplitude of the first twitch (Train-of-Four > or = 0.7). MEASUREMENTS AND MAIN RESULTS: These patients included the only three patients with status asthmaticus in our study. The groups were similar with respect to age, sex, weight, Acute Physiology and Chronic Health Evaluation II score, mode of ventilation, creatinine clearance, indications for paralysis, and duration of pancuronium administration. The median time for patients to recover from paralysis was 3.5 hrs (95% confidence interval, 1.82-5.18) in the infusion group vs. 6.3 hrs (95% confidence interval, 3.40-9.19) in the intermittent bolus group (p = .10). Less drug was administered in the intermittent group (mean, 0.02+/-0.01 mg/kg/hr) than by infusion (mean, 0.04+/-0.01 mg/kg/hr; p < .001). Six patients (five in the infusion group and one in the intermittent group) developed persistent severe muscle weakness. In addition, six different patients (three from each group) had prolonged recovery >12 hrs. CONCLUSIONS: Our study suggests that recovery time after paralysis with continuous infusion is faster than that after intermittent bolus injection. Although more pancuronium was administered in the continuous-infusion group, recovery time was not prolonged as a consequence. It is uncertain whether pancuronium given by infusion increases the risk of persistent muscle weakness.

APACHE↗

PubMed1993

Induction of experimental autoimmune myasthenia gravis with acetylcholine receptors using a nonionic block copolymer as adjuvant.

To induce autoimmune diseases in animals, the auto-antigen has to be emulsified in adjuvants (e.g., complete Freund's adjuvant) containing microbial products such as Mycobacterium tuberculosis. But these powerful immunoadjuvants are not without undesirable immune response to the microbial proteins and induction of adjuvant arthritis, which could interfere with the antigen specific autoimmune response to be tested. This study was performed to evaluate the requirement of microbial products in the induction of experimental autoimmune diseases, and to identify an adjuvant without unwanted immune responses. C57BL/6 mice were inoculated with Torpedo acetylcholine receptors (T-AChR) emulsified in Titermax (TM), an adjuvant containing nonionic block copolymer and no microbial products, and evaluated for experimental autoimmune myasthenia gravis (EAMG) susceptibility. Mice immunized with T-AChR in TM demonstrated characteristic myasthenic muscle weakness with electrophysiological defect, elevated serum anti-AChR antibodies, and muscle AChR loss. None of the mice that received TM alone had muscle weakness, serum anti-AChR antibodies or muscle AChR loss. The data imply that microbial products are not critical in the induction of autoimmune diseases like myasthenia gravis in mice. Further, nonionic block copolymer could be an ideal adjuvant in the induction of autoimmune diseases in animals.

Adjuvants, Immunologic↗

PubMed1989

Skeletal muscle disorders and associated factors that limit exercise performance.

The study of skeletal muscle disorders is providing potentially important insights into regulatory mechanisms in human exercise and fatigue and information useful for diagnostic and treatment purposes. This review primarily concerned the general metabolic and physiological factors which set upper limits to performance of various types of exercise in patients with a variety of muscle disorders. From the standpoint of exercise performance, skeletal muscle diseases can be classified into three major groups. One group consists of primary disorders of muscle energy metabolism, including defects in muscle carbohydrate and lipid metabolism, disorders of mitochondrial electron transport, and abnormalities of purine nucleotide metabolism. Exercise performance largely reflects the capacity for ATP resynthesis. Oxidative phosphorylation is the dominant quantitative source of energy for ATP resynthesis under most exercise conditions. Consequently, patients with disordered oxidative metabolism (i.e., patients with defects in the availability or utilization of oxidizable substrate, such as those with phosphorylase or PFK deficiency or those with defects in mitochondrial electron transport) typically demonstrate severely impaired exercise performance. Intolerance to sustained exercise and premature fatigability are salient features of muscle oxidative disorders. Maximal oxygen uptake and maximal a-v O2 difference are markedly subnormal related to an attenuated muscle oxygen extraction. Muscle weakness and atrophy are less common. Anaerobic muscle performance is dramatically limited in patients with virtually complete defects of glycogenolysis/glycolysis but appears relatively normal in those with electron transport defects. A second major group of disorders includes patients with decreased muscle mass due to muscle necrosis, atrophy, and replacement of muscle by fat and connective tissue. These disorders are exemplified by the various muscular dystrophies (Duchenne's dystrophy, Becker's dystrophy, LG dystrophy, FSH dystrophy, and myotonic dystrophy) in which exercise performance is severely impaired due to muscle wasting and weakness in spite of largely normal pathways for muscle ATP resynthesis. In muscular dystrophy patients, the degree to which maximal oxygen uptake and anaerobic muscle performance are impaired appears to be a function of the severity of muscle weakness and atrophy. A third group of disorders includes patients with impaired activation of muscle contraction or relaxation. These disorders may be considered in two subcategories. In the first, impaired activation or relaxation of contractile activity is due to intrinsic muscle dysfunction (e.g., diseases associated with myotonia or periodic paralysis). In the second subcategory, there is impaired muscle activation due to a primary abnormality in the central nervous system, motor nerves, or neuromuscular junction.(ABSTRACT TRUNCATED AT 400 WORDS)

Efficiency↗