Muscle fibre characteristics and lactate responses to exercise in chronic fatigue syndrome

OBJECTIVES—To examine the proportions of type 1 and type 2 muscle fibres and the degree of muscle fibre atrophy andhypertrophy in patients with chronic fatigue syndrome in relation tolactate responses to exercise, and to determine to what extent anyabnormalities found might be due to inactivity.
METHODS—Quadriceps needle muscle biopsies wereobtained from 105 patients with chronic fatigue syndrome and theproportions of type 1 and 2 fibres and fibre atrophy and hypertrophyfactors were determined from histochemical preparations, using asemiautomated image analysis system. Forty one randomly selectedbiopsies were also examined by electron microscopy. Lactate responsesto exercise were measured in the subanaerobic threshold exercise test (SATET).
RESULTS—Inactivity would be expected to result ina shift to type 2 fibre predominance and fibre atrophy, but type 1 predominance (23%) was more common than type 2 predominance (3%), andfibre atrophy was found in only 10.4% of cases. Patients withincreased lactate responses to exercise did have significantly fewertype 1 muscle fibres (p<0.043 males, p<0.0003 females), but there was no evidence that this group was less active than the patients withnormal lactate responses. No significant ultrastructural abnormalitieswere found.
CONCLUSION—Muscle histometry in patients withchronic fatigue syndrome generally did not show the changes expected asa result of inactivity. However, patients with abnormal lactateresponses to exercise had a significantly lower proportion ofmitochondria rich type 1 muscle fibres.

     

Cortical and motor responses to acute forced exercise in Parkinson's disease

IntroductionStudies in animal models of Parkinson's disease (PD) have suggested that the rate of exercise performance is important in treatment efficacy and neuroprotection. In humans with PD, lower-extremity forced-exercise (FE) produced global improvements in motor symptoms based on clinical ratings and biomechanical measures of upper extremity function.MethodsfMRI was used to compare the underlying changes in brain activity in PD patients following the administration of anti-parkinsonian medication and following a session of FE.ResultsNine individuals with PD completed fMRI scans under each condition: off anti-PD medication, on anti-PD medication, and off medication + FE. Unified Parkinson's Disease Rating Motor Scale scores improved by 50% in the FE condition compared to the off-medication condition. The pattern of fMRI activation after FE was similar to that seen with anti-PD medication. Direct comparison of the fMRI activation patterns showed high correlation between FE and anti-PD medication.ConclusionThese findings suggest that medication and FE likely utilize the same pathways to produce symptomatic relief in individuals with PD.     

Norepinephrine and cardiovascular responses to maximal exercise in Parkinson's disease on and off medication

The aim of this experiment is to understand how Parkinson's disease (PD) medication affects the autonomic responses of individuals during an acute exercise stress test. Fourteen people with PD and fifteen healthy individuals age‐matched between 50 and 80 years performed a modified Bruce protocol. Subjects with PD performed the test once off medication (PD‐off) and then 1 week later on medication (PD‐on). Heart rate (HR), blood pressure (BP), VO₂, and norepinephrine (NE) levels were taken at rest and at peak exercise. At peak exercise HR, BP, and NE values for the PD‐on and PD‐off group were all significantly lower than healthy controls, regardless of whether subjects were on their medication. Autonomic abnormalities during exercise in this population appear to be disease manifested and not impactedby medications used to treat PD. We can assume, both on and off medication, this population will show markedly lower BP, HR, and NE responses. © 2009 Movement Disorder Society     

Muscle weakness and intolerance to exercise in mitochondrial myopathies

Muscle weakness and intolerance to exercise are two of the main features commonly shown by patients affected by mitochondrial myopathies. In order to obtain an objective and quantitative evaluation of muscle weakness and endurance, we studied an evaluation protocol devoted to the assessment of 1) muscle strength by the isokinetic ergometer and 2) the metabolic aspects of exercise by means of Maximal Oxygen Consumption and endurance by a Steady State Submaximal exercise evaluation. The protocol has been applied to the study of patients affected by mitochondrial diseases and proved to be a reliable method to quantitate the defect in the oxidation pathways, either before or during the therapeutic follow-up.     

Muscle chemoreflexes and exercise in humans

This review focuses on the role afferent nerves from the contracting muscles play in linking muscle metabolism to the cardiovascular adjustments during exercise by means of a muscle chemoreflex. In the 1930s Alam and Smirk provided the first clear evidence that human (and animal) skeletal muscles are innervated by chemosensitive afferents that can evoke increases in arterial blood pressure. They proposed that the purpose of the increase in pressure was to improve blood flow to the active muscles. Subsequent studies have identified the slowly conducting group IV afferents as the major class of fibres participating in the sensory arm of this reflex. Most of these fibres travel via the dorsal roots to the ipsilateral spinal cord where they synapse in the substantia gelatinosa and release substance P or other peptide transmitters. The second order (or higher) neurons cross to the contralateral side of the spinal cord and travel rostrally to stimulate brainstem cardiovascular centres and increase arterial pressure. Current evidence favours the concept that substances associated with muscle acidosis provide the stimulus to the afferents. In humans, chemosensitive afferent activation causes a marked increase in vasoconstrictor efferent muscle sympathetic nerve activity. It is unclear if the muscle chemoreflex improves blood flow to underperfused active muscles by augmenting arterial pressure, or if the increase in sympathetic outflow restrains metabolic vasodilatation to regulate arterial blood pressure during activities like running or cycling.     

Hormonal responses to exercise in chronic fatigue syndrome

Chronic fatigue syndrome (CFS) is a debilitating disease characterized by severe, unexplained fatigue and postexertional exacerbation of symptoms. We examined basal endocrine function in a group of CFS patients and a carefully matched group of sedentary controls. The subjects then completed a graded, maximal exercise test on a treadmill, and additional blood samples were drawn 4 min and a day after the end of exercise. There were no differences in basal hormone levels before exercise. Plasma adrenocorticotropin, epinephrine, prolactin and thyrotropin responses 4 min after exercise were lower in the CFS group, but the growth hormone response may have been exaggerated, and the plasma norepinephrine response was similar to that in controls. The next day, there were no differences in hormone levels between the groups, which suggests that long-term changes in endocrine function are unlikely to be a cause of the prolonged fatigue that occurs in CFS patients after a bout of exertion.     

肌肉运动与骨骼肌细胞的凋亡

背景：不少医学研究表明,细胞凋亡能导致大量自由基增多、Ca2+浓度升高、线粒体膜电位下降引起运动能力的下降。因此,研究细胞凋亡与运动训练的关系意义重要。 目的：总结与探索关于肌肉运动与骨骼肌细胞凋亡的相关问题。 方法：计算机检索中国期刊全文数据(网址http://dlib.cnki.net/kns50/index.aspx)及PubMed数据库(网址http://www.ncbi.nlm.nih.gov/pubmed/ )1990-01/2009-06期间的相关文章,检索词为“肌肉运动,骨骼肌细胞凋亡,muscle exercise,apoptosis in the skeletal muscle”。纳入与肌肉运动与骨骼肌细胞的凋亡研究现状与发展密切相关。①有关骨骼肌细胞凋亡的研究。②运动与骨骼肌细胞凋亡研究。③运动诱发骨骼肌细胞凋亡的基因调控研究。④骨骼肌细胞凋亡的分子机制研究。⑤同一领域选择近期发表或在权威杂志上发表的文章。排除重复性研究。 结果与结论：运动后,正常肌肉中或是病理状态下的肌肉中骨骼肌细胞都会出现凋亡,凋亡的形态学表现与普通凋亡细胞相似,即核固缩、质膜发泡、细胞器紧缩,凋亡小体形成,其凋亡过程大致可分为3个阶段,即启始阶段、效应阶段和降解阶段。骨骼肌细胞凋亡的增加是导致运动性疲劳的重要原因。目前国内外对骨骼肌细胞凋亡的基因调控研究主要是从 凋亡调控因子Bcl-2蛋白、肿瘤坏死因子α及死亡蛋白酶半胱氨酸天冬氨酸酶着手。bcl-2基因蛋白的抗凋亡作用主要是通过阻止线粒体通透性转换孔的开放,阻止线粒体释放促凋亡蛋白、防止线粒体膜脂质过氧化以及线粒体基质Ca2+释放实现的。肿瘤坏死因子家族在启动死亡因子及其受体途径中起重要作用,此途径的启动依赖于死亡配体与死亡受体相结合,激活半胱氨酸天冬氨酸酶,导致细胞凋亡。通过研究探索运动强度与骨骼肌细胞凋亡及坏死的界限关系,有利于在运动中认识运动性疲劳产生的机制及有效消除疲劳。     

Early inflammatory and myogenic responses to resistance exercise in the elderly

Introduction and Methods: This study compared changes in myokine and myogenic genes following resistance exercise (3 sets of 12 repetitions of maximal unilateral knee extension) in 20 elderly men (67.8 ± 1.0 years) and 15 elderly women (67.2 ± 1.5 years). Results: Monocyte chemotactic protein (MCP)-1, macrophage inhibitory protein (MIP)-1β, interleukin (IL)-6 and MyoD mRNA increased significantly (P < 0.05), whereas myogenin and myostatin mRNA decreased significantly after exercise in both groups. Macrophage-1 (Mac-1) and MCP-3 mRNA did not change significantly after exercise in either group. MIP-1β, Mac-1 and myostatin mRNA were significantly higher before and after exercise in men compared with women. In contrast, MCP-3 and myogenin mRNA were significantly higher before and after exercise in the women compared with the men. Conclusions: In elderly individuals, gender influences the mRNA expression of certain myokines and growth factors, both at rest and after resistance exercise. These differences may influence muscle regeneration following muscle injury. Muscle Nerve 46: 407-412, 2012.     

The effect of COMT inhibition with entacapone on cardiorespiratory responses to exercise in patients with Parkinson's disease

The inhibition of catechol-O-methyltransferase (COMT) may impair catecholamine clearance resulting in unwanted cardiac and hemodynamic events. We therefore studied the effects of entacapone, an inhibitor of peripheral COMT, on cardiorespiratory and plasma noradrenaline (NA) responses to exercise and on respiratory muscle strength in l-dopa treated patients with Parkinson's disease (PD). A randomized, double-blind, cross-over study with two 1week treatment periods was performed in 15 PD patients. The test battery included analysis of hemodynamics, gas exchange parameters and plasma NA during a maximal exercise test, assessment of maximal static airway pressures and pre- and post-exercise motor scores of the Unified Parkinson's Disease Rating Scale (UPDRS). The first test was done after withholding l-dopa overnight ('run-in' test, off-phase). The second and third tests were done in on-phase after 1week treatment with either entacapone 200mg or placebo given with each dose of l-dopa. No differences in maximal work load, plasma NA, or in cardiorespiratory responses to either maximal or work rate standardized submaximal exercise were observed between entacapone and placebo, except for O(2) pulse, which was slightly lower (p < 0.05) after entacapone at submaximal exercise level. Maximal airway pressures were similar between the study treatments and run-in. Exercise had no effect on motor UPDRS after either study treatment or during the run-in test. No serious adverse events were observed. The results of this study suggest that entacapone does not change the work capacity, work efficiency or respiratory muscle strength in l-dopa treated PD patients with mild to moderate disease severity, and that its use with l-dopa seems to be safe in conditions of maximal physical effort. However, data from the long-term use of COMT inhibitors are needed to confirm these findings.     

Cardiopulmonary and metabolic responses to maximum exercise and aerobic capacity in hemiplegic patients

This study evaluated cardiopulmonary and metabolic responses to maximum exercise and aerobic capacity in hemiplegic patients and clarified the relationship between the resulting data and motor disability. Twenty patients with stroke and fifteen healthy controls were included in the study. Cardiopulmonary and metabolic responses to maximum exercise were investigated with an electronically braked arm crank ergometer. Vital capacity, forced expiratory volume in 1 second, peak expiratory flow rate, forced vital capacity, maximum voluntary ventilation, peak power output, respiratory exchange ratio, and exercise time were reduced in stroke patients when compared with the controls. No relationship was found between these data and motor disability. The hemiplegic patients showed a significant respiratory dysfunction and reduced exercise tolerance. These findings suggest that a program of ventilatory and aerobic training should be considered early after stroke to avoid cardiorespiratory problems and deconditioning.     

Neuroendocrine responses to physostigmine in Alzheimer's disease

To assess central nervous system cholinergic neuroendocrine regulation in Alzheimer's disease (AD), we measured plasma arginine vasopressin, beta-endorphin, and epinephrine responses to a cholinergic challenge elicited by intravenous administration of the acetylcholinesterase inhibitor physostigmine (0.0125 mg/kg) in male patients with AD (n = 12) and compared their responses with those of age-matched normal control subjects (n = 12). Physostigmine promptly increased plasma arginine vasopressin (tenfold), beta-endorphin (twofold to threefold) and epinephrine (threefold) levels in elderly control subjects. In contrast, patients with AD showed attenuated responses to physostigmine. When controls and patients with AD who experienced nausea (n = 2 and n = 6, respectively) were excluded, the arginine vasopressin, beta-endorphin, and epinephrine responses of patients with AD were significantly less than those of control subjects. These data suggest that the central nervous system cholinergic deterioration of AD results in decreased responsiveness of neuroendocrine systems that are regulated by central cholinergic mechanisms.     

Muscle metabolic economy is inversely related to exercise intensity and type II myofiber distribution

It is not known what causes the well-established inverse relationship between whole-body exercise economy and exercise intensity. The purpose of this study was to: (1) evaluate muscle exercise economy at 45%, 70%, and maximum isometric strength using 31P magnetic resonance spectroscopy (31P-MRS); and (2) determine the relationship between percent type II muscle fiber cross-section, whole-body exercise economy, and muscle exercise economy. Subjects included 32 premenopausal women. Muscle exercise economy was significantly different across the three exercise intensities (28.1 +/- 10.4, 24.8 +/- 8.2, and 20.2 +/- 7.5 N/cm2. mmol/L adenosine triphosphate [ATP] for the 45%, 70%, and maximum intensities, respectively). Percent type II muscle area was significantly related to whole-body metabolic economy during activities of daily living (r = -0.68) and 31P-MRS muscle metabolic economy during isometric plantar flexion (r = -0.53). These data suggest that skeletal muscle becomes less economical as force production increases, and that these decreases in metabolic economy may be related to increased dependence on inefficient type II muscle.     

Muscle sympathetic responses during orthostasis in heat-stressed individuals

Purpose  

Whole-body heat stress compromises the control of blood pressure during an orthostatic challenge, although the extent to which this occurs can vary greatly between individuals. The mechanism(s) responsible for these varying responses remain unclear. This study tested the hypothesis that the individuals who are best able to tolerate an orthostatic challenge while heat stressed are the ones with the largest increase in sympathetic activity during orthostasis, indexed from recordings of muscle sympathetic nerve activity (MSNA).     

Prothrombotic responses to exercise are little influenced by clopidogrel treatment

AIMS: Adenosine diphosphate (ADP) is involved in shear-induced platelet activation, which may be important for platelet responses to stress. We therefore tested the hypothesis that ADP receptor antagonism by clopidogrel treatment would attenuate exercise-induced platelet activation. METHODS AND RESULTS: Fifteen healthy volunteers performed exhaustive exercise without and with clopidogrel pretreatment (75 mg/day; 7 days) in a randomised crossover study. Filtragometry readings (reflecting platelet aggregability in vivo) and 11-dehydro-thromboxane B(2) (TxM) in plasma were determined before and after exercise. Platelet and leukocyte activity, platelet-platelet (PPA), and platelet-leukocyte aggregates (PLAs) in vivo and their responsiveness to agonist stimulation in vitro were assessed by flow cytometry. Clopidogrel treatment inhibited ADP-induced platelet P-selectin expression by 72% (54-85%). Exercise increased platelet aggregation (filtragometry and PPAs), elevated plasma TxM, increased single platelet P-selectin expression, elevated circulating PLAs, and enhanced ADP and thrombin-stimulated P-selectin expression. Clopidogrel prolonged filtragometry readings and attenuated agonist stimulated P-selectin expression at rest, but did not influence TxM in plasma or urine or attenuate platelet or leukocyte responses to exercise. Clopidogrel treatment did not influence plasma CD40L (ligand) at rest or after exercise. CONCLUSION: Clopidogrel treatment attenuates platelet activity in vivo at rest, but exercise counteracts the platelet stabilizing effects of clopidogrel. The hypothesis that ADP is involved in stress-induced platelet activation was not supported.     

Technology-aided programs to support exercise of adaptive head responses or leg-foot and hands responses in children with multiple disabilities

Objective: Assessing the effectiveness of technology-aided programs to help three children with multiple disabilities exercise adaptive head or leg-foot and hands responses independently.

Method: The response selected for the two children included in Study I was head rotation (i.e. movements of at least 25 degrees to the left that could start from a full right position as well as from other positions). The responses selected for the child included in Study II involved forward movement of the left leg-foot and forward movement of his hand(s) to touch objects. Tilt or optic microswitches were used to monitor the responses and a computer system regulated the stimuli contingent on them.

Results: The responses targeted in the two studies showed large frequency increases during the intervention phases of the studies (i.e. when followed by stimulation).

Conclusion: Technology-aided programs can be a useful resource to help children with multiple disabilities exercise relevant responses independently.