Página 11 dos resultados de 35240 itens digitais encontrados em 0.015 segundos

Exercise induces expression of leukaemia inhibitory factor in human skeletal muscle

Broholm, Christa; Mortensen, Ole Hartvig; Nielsen, Søren; Akerstrom, Thorbjorn; Zankari, Alaa; Dahl, Benny; Pedersen, Bente Klarlund
Fonte: Blackwell Science Inc Publicador: Blackwell Science Inc
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
36.54%
The leukaemia inhibitory factor (LIF) belongs to the interleukin (IL)-6 cytokine superfamily and is constitutively expressed in skeletal muscle. We tested the hypothesis that LIF expression in human skeletal muscle is regulated by exercise. Fifteen healthy young male volunteers performed either 3 h of cycle ergometer exercise at ∼60% of (n = 8) or rested (n = 7). Muscle biopsies were obtained from the vastus lateralis prior to exercise, immediately after exercise, and at 1.5, 3, 6 and 24 h post exercise. Control subjects had biopsy samples taken at the same time points as during the exercise trial. Skeletal muscle LIF mRNA increased immediately after the exercise and declined gradually during recovery. However, LIF protein was unchanged at the investigated time points. Moreover, we tested the hypothesis that LIF mRNA and protein expressions are modulated by calcium (Ca2+) in primary human skeletal myocytes. Treatment of myocytes with the Ca2+ ionophore, ionomycin, for 6 h resulted in an increase in both LIF mRNA and LIF protein levels. This finding suggests that Ca2+ may be involved in the regulation of LIF in endurance-exercised skeletal muscle. In conclusion, primary human skeletal myocytes have the capability to produce LIF in response to ionomycin stimulation and LIF mRNA levels increase in skeletal muscle following concentric exercise. The finding that the increase in LIF mRNA levels is not followed by a similar increase in skeletal muscle LIF protein suggests that other exercise stimuli or repetitive stimuli are necessary in order to induce a detectable accumulation of LIF protein.

Exercise promotes α7 integrin gene transcription and protection of skeletal muscle

Boppart, Marni D.; Volker, Sonja E.; Alexander, Nicole; Burkin, Dean J.; Kaufman, Stephen J.
Fonte: American Physiological Society Publicador: American Physiological Society
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
36.54%
The α7β1 integrin is increased in skeletal muscle in response to injury-producing exercise, and transgenic overexpression of this integrin in mice protects against exercise-induced muscle damage. The present study investigates whether the increase in the α7β1 integrin observed in wild-type mice in response to exercise is due to transcriptional regulation and examines whether mobilization of the integrin at the myotendinous junction (MTJ) is a key determinant in its protection against damage. A single bout of downhill running exercise selectively increased transcription of the α7 integrin gene in 5-wk-old wild-type mice 3 h postexercise, and an increased α7 chain was detected in muscle sarcolemma adjacent to tendinous tissue immediately following exercise. The α7B, but not α7A isoform, was found concentrated and colocalized with tenascin-C in muscle fibers lining the MTJ. To further validate the importance of the integrin in the protection against muscle damage following exercise, muscle injury was quantified in α7−/− mice. Muscle damage was extensive in α7−/− mice in response to both a single and repeated bouts of exercise and was largely restricted to areas of high MTJ concentration and high mechanical force near the Achilles tendon. These results suggest that exercise-induced muscle injury selectively increases transcription of the α7 integrin gene and promotes a rapid change in the α7β integrin at the MTJ. These combined molecular and cellular alterations are likely responsible for integrin-mediated attenuation of exercise-induced muscle damage.

Age-related differences in the dose–response relationship of muscle protein synthesis to resistance exercise in young and old men

Kumar, Vinod; Selby, Anna; Rankin, Debbie; Patel, Rekha; Atherton, Philip; Hildebrandt, Wulf; Williams, John; Smith, Kenneth; Seynnes, Olivier; Hiscock, Natalie; Rennie, Michael J
Fonte: Blackwell Science Inc Publicador: Blackwell Science Inc
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
36.54%
We investigated how myofibrillar protein synthesis (MPS) and muscle anabolic signalling were affected by resistance exercise at 20–90% of 1 repetition maximum (1 RM) in two groups (25 each) of post-absorptive, healthy, young (24 ± 6 years) and old (70 ± 5 years) men with identical body mass indices (24 ± 2 kg m−2). We hypothesized that, in response to exercise, anabolic signalling molecule phosphorylation and MPS would be modified in a dose-dependant fashion, but to a lesser extent in older men. Vastus lateralis muscle was sampled before, immediately after, and 1, 2 and 4 h post-exercise. MPS was measured by incorporation of [1,2-13C] leucine (gas chromatography–combustion–mass spectrometry using plasma [1,2-13C]α-ketoisocaparoate as surrogate precursor); the phosphorylation of p70 ribosomal S6 kinase (p70s6K) and eukaryotic initiation factor 4E binding protein 1 (4EBP1) was measured using Western analysis with anti-phosphoantibodies. In each group, there was a sigmoidal dose–response relationship between MPS at 1–2 h post-exercise and exercise intensity, which was blunted (P < 0.05) in the older men. At all intensities, MPS fell in both groups to near-basal values by 2–4 h post-exercise. The phosphorylation of p70s6K and 4EBP1 at 60–90% 1 RM was blunted in older men. At 1 h post-exercise at 60–90% 1 RM...

Exercise and adrenaline increase PGC-1α mRNA expression in rat adipose tissue

Sutherland, Lindsey N; Bomhof, Marc R; Capozzi, Lauren C; Basaraba, Susan A U; Wright, David C
Fonte: Blackwell Science Inc Publicador: Blackwell Science Inc
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
36.54%
The purpose of the present investigation was to explore the effects of exercise and adrenaline on the mRNA expression of PGC-1α, a master regulator of mitochondrial biogenesis, in rat abdominal adipose tissue. We hypothesized that (1) exercise training would increase PGC-1α mRNA expression in association with increases in mitochondrial marker enzymes, (2) adrenaline would increase PGC-1α mRNA expression and (3) the effect of exercise on PGC-1α mRNA expression in white adipose tissue would be attenuated by a β-blocker. Two hours of daily swim training for 4 weeks led to increases in mitochondrial marker proteins and PGC-1α mRNA expression in epididymal and retroperitoneal fat depots. Additionally, a single 2 h bout of exercise led to increases in PGC-1α mRNA expression immediately following exercise cessation. Adrenaline treatment of adipose tissue organ cultures led to dose-dependent increases in PGC-1α mRNA expression. A supra-physiological concentration of adrenaline increased PGC-1α mRNA expression in epididymal but not retroperitoneal adipose tissue. β-Blockade attenuated the effects of an acute bout of exercise on PGC-1α mRNA expression in epididymal but not retroperitoneal fat pads. In summary, this is the first investigation to demonstrate that exercise training...

Sympathetic restraint of muscle blood flow during hypoxic exercise

Stickland, Michael K.; Smith, Curtis A.; Soriano, Benjamin J.; Dempsey, Jerome A.
Fonte: American Physiological Society Publicador: American Physiological Society
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
36.54%
Control of exercising muscle blood flow is a balance between local vasodilatory factors and the increase in global sympathetic vasoconstrictor outflow. Hypoxia has been shown to potentiate the muscle sympathetic nerve response to exercise, potentially limiting the increase in muscle blood flow. Accordingly, we investigated sympathetic restraint to exercising muscle during whole body exercise in hypoxia. Six dogs chronically instrumented with ascending aortic and hindlimb flow probes and a terminal aortic catheter were studied at rest and mild [2.5 miles/h (mph), 5% grade] and moderate (4.0 mph, 10% grade) exercise while breathing room air or hypoxia (PaO2 ∼45 mmHg) in the intact control condition and following systemic α-adrenergic blockade (phentolamine). Hypoxia caused an increase in cardiac output (CO), hindlimb flow (FlowL), and blood pressure (BP), while total (CondT) and hindlimb conductance (CondL) were unchanged at rest and mild exercise but increased with moderate exercise. During both mild and moderate exercise, α-blockade in normoxia resulted in significant vasodilation as evidenced by increases in CO (10%), FlowL (17%), CondT (33%), CondL (43%), and a decrease in BP (−18%), with the increase in CondL greater than the increase in CondT during mild exercise. Compared with the normoxic response...

Reduced muscle activation during exercise related to brain oxygenation and metabolism in humans

Rasmussen, P; Nielsen, J; Overgaard, M; Krogh-Madsen, R; Gjedde, A; Secher, N H; Petersen, N C
Fonte: Blackwell Science Inc Publicador: Blackwell Science Inc
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
36.54%
Maximal exercise may be limited by central fatigue defined as an inability of the central nervous system to fully recruit the involved muscles. This study evaluated whether a reduction in the cerebral oxygen-to-carbohydrate index (OCI) and in the cerebral mitochondrial oxygen tension relate to the ability to generate a maximal voluntary contraction and to the transcranial magnetic stimulated force generation. To determine the role of a reduced OCI and in central fatigue, 16 males performed low intensity, maximal intensity and hypoxic cycling exercise. Exercise fatigue was evaluated by ratings of perceived exertion (RPE), arm maximal voluntary force (MVC), and voluntary activation of elbow flexor muscles assessed with transcranial magnetic stimulation. Low intensity exercise did not produce any indication of central fatigue or marked cerebral metabolic deviations. Exercise in hypoxia ( 0.10) reduced cerebral oxygen delivery ∼25% and decreased 11 ± 4 mmHg (P < 0.001) together with OCI (6.2 ± 0.7 to 4.8 ± 0.5, P < 0.001). RPE increased while MVC and voluntary activation were reduced (P < 0.05). During maximal exercise declined 8 ± 4 mmHg (P < 0.05) and OCI to 3.8 ± 0.5 (P < 0.001). RPE was 18.5, and MVC and voluntary activation were reduced (P < 0.05). We observed no signs of muscular fatigue in the elbow flexors and all control MVCs were similar to resting values. Exhaustive exercise provoked cerebral deoxygenation...

Resistance exercise volume affects myofibrillar protein synthesis and anabolic signalling molecule phosphorylation in young men

Burd, Nicholas A; Holwerda, Andrew M; Selby, Keegan C; West, Daniel W D; Staples, Aaron W; Cain, Nathan E; Cashaback, Joshua G A; Potvin, James R; Baker, Steven K; Phillips, Stuart M
Fonte: Blackwell Science Inc Publicador: Blackwell Science Inc
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
36.54%
We aimed to determine if any mechanistic differences exist between a single set (1SET) and multiple sets (i.e. 3 sets; 3SET) of resistance exercise by utilizing a primed constant infusion of [ring-13C6]phenylalanine to determine myofibrillar protein synthesis (MPS) and Western blot analysis to examine anabolic signalling molecule phosphorylation following an acute bout of resistance exercise. Eight resistance-trained men (24 ± 5 years, BMI = 25 ± 4 kg m−2) were randomly assigned to perform unilateral leg extension exercise at 70% concentric one repetition maximum (1RM) until volitional fatigue for 1SET or 3SET. Biopsies from the vastus lateralis were taken in the fasted state (Fast) and fed state (Fed; 20 g of whey protein isolate) at rest, 5 h Fed, 24 h Fast and 29 h Fed post-exercise. Fed-state MPS was transiently elevated above rest at 5 h for 1SET (2.3-fold) and returned to resting levels by 29 h post-exercise. However, the exercise induced increase in MPS following 3SET was superior in amplitude and duration as compared to 1SET at both 5 h (3.1-fold above rest) and 29 h post-exercise (2.3-fold above rest). Phosphorylation of 70 kDa S6 protein kinase (p70S6K) demonstrated a coordinated increase with MPS at 5 h and 29 h post-exercise such that the extent of p70S6K phosphorylation was related to the MPS response (r = 0.338...

Influence of exercise intensity on skeletal muscle blood flow, O2 extraction and O2 uptake on-kinetics

Jones, Andrew M; Krustrup, Peter; Wilkerson, Daryl P; Berger, Nicolas J; Calbet, José A; Bangsbo, Jens
Fonte: Blackwell Science Inc Publicador: Blackwell Science Inc
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
36.54%
Following the start of low-intensity exercise in healthy humans, it has been established that the kinetics of skeletal muscle O2 delivery is faster than, and does not limit, the kinetics of muscle O2 uptake (). Direct data are lacking, however, on the question of whether O2 delivery might limit kinetics during high-intensity exercise. Using multiple exercise transitions to enhance confidence in parameter estimation, we therefore investigated the kinetics of, and inter-relationships between, muscle blood flow (), a– difference and following the onset of low-intensity (LI) and high-intensity (HI) exercise. Seven healthy males completed four 6 min bouts of LI and four 6 min bouts of HI single-legged knee-extension exercise. Blood was frequently drawn from the femoral artery and vein during exercise and , a– difference and were calculated and subsequently modelled using non-linear regression techniques. For LI, the fundamental component mean response time (MRTp) for kinetics was significantly shorter than kinetics (mean ± SEM, 18 ± 4 vs. 30 ± 4 s; P < 0.05), whereas for HI, the MRTp for and was not significantly different (27 ± 5 vs. 29 ± 4 s, respectively). There was no difference in the MRTp for either or between the two exercise intensities; however...

Effect of resistance exercise contraction mode and protein supplementation on members of the STARS signalling pathway

Vissing, Kristian; Rahbek, Stine K; Lamon, Severine; Farup, Jean; Stefanetti, Renae J; Wallace, Marita A; Vendelbo, Mikkel H; Russell, Aaron
Fonte: Blackwell Science Inc Publicador: Blackwell Science Inc
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
36.54%
The striated muscle activator of Rho signalling (STARS) pathway is suggested to provide a link between external stress responses and transcriptional regulation in muscle. However, the sensitivity of STARS signalling to different mechanical stresses has not been investigated. In a comparative study, we examined the regulation of the STARS signalling pathway in response to unilateral resistance exercise performed as either eccentric (ECC) or concentric (CONC) contractions as well as prolonged training; with and without whey protein supplementation. Skeletal muscle STARS, myocardian-related transcription factor-A (MRTF-A) and serum response factor (SRF) mRNA and protein, as well as muscle cross-sectional area and maximal voluntary contraction, were measured. A single-bout of exercise produced increases in STARS and SRF mRNA and decreases in MRTF-A mRNA with both ECC and CONC exercise, but with an enhanced response occurring following ECC exercise. A 31% increase in STARS protein was observed exclusively after CONC exercise (P < 0.001), while pSRF protein levels increased similarly by 48% with both CONC and ECC exercise (P < 0.001). Prolonged ECC and CONC training equally stimulated muscle hypertrophy and produced increases in MRTF-A protein of 125% and 99%...

Treadmill exercise improves spatial learning ability by enhancing brain-derived neurotrophic factor expression in the attention-deficit/hyperactivity disorder rats

Jeong, Hye Im; Ji, Eun-Sang; Kim, Su-Hyun; Kim, Tae-Wook; Baek, Sang-Bin; Choi, Seung Wook
Fonte: Korean Society of Exercise Rehabilitation Publicador: Korean Society of Exercise Rehabilitation
Tipo: Artigo de Revista Científica
Publicado em 30/06/2014 Português
Relevância na Pesquisa
36.54%
Attention-deficit/hyperactivity disorder (ADHD) patients show learning difficulty and impulsiveness. Exercise is known to improve learning ability and memory function. In the present study, we investigated the duration-dependence of the effect of treadmill exercise on spatial learning ability in relation with brain-derived neurotrophic factor (BDNF) expression in ADHD rats. For this study, radial 8-arm maze test and western blot for BDNF and tyrosine kinase B (TrkB) were performed. Spontaneous hypertensive rats were used as the ADHD rats and Wistar-Kyoto rats were used as the control rats. The rats in the exercise groups were forced to run on a treadmill for 10 min, 30 min, and 60 min once a day for 28 consecutive days. ADHD rats displayed impairment of spatial learning ability, in contrast treadmill exercise ameliorated impairment of spatial learning ability. Treadmill exercise for 30 min per day showed most potent ameliorating effect on impairment of spatial learning ability. BDNF and TrkB expressions in the hippocampus were decreased in the ADHD rats, in contrast treadmill exercise enhanced BDNF and TrkB expressions. Treadmill exercise for 30 min and for 60 min per day showed enhancing effects on BDNF and TrkB expressions. Treadmill exercise alleviated deficits in the spatial learning ability through enhancing BDNF and TrkB expressions in the ADHD rats. Treadmill exercise for 30 min per day can be considered as the most effective therapeutic modality for the ADHD symptoms.

Treadmill exercise prevents GABAergic neuronal loss with suppression of neuronal activation in the pilocarpine-induced epileptic rats

Lim, Baek-Vin; Shin, Mal-Soon; Lee, Jae-Min; Seo, Jin-Hee
Fonte: Korean Society of Exercise Rehabilitation Publicador: Korean Society of Exercise Rehabilitation
Tipo: Artigo de Revista Científica
Publicado em 30/04/2015 Português
Relevância na Pesquisa
36.54%
Epilepsy is a common neurological disorder characterized by seizure and loss of neuronal cells by abnormal rhythmic firing of neurons in the brain. In the present study, we investigated the effect of treadmill exercise on gamma-aminobutyric acid (GABA)ergic neuronal loss in relation with neuronal activation using pilocarpine-induced epileptic rats. The rats were divided into four groups: control group, control and treadmill exercise group, pilocarpine-induced epilepsy group, and pilocarpine-induced epilepsy and treadmill exercise group. Epilepsy was induced by intraperitoneal injection of 320 mg/kg pilocarpine hydrochloride. The rats in the exercise groups were forced to run on a motorized treadmill for 30 min once a day for 2 weeks. In the present results, neuronal loss in the hippocampal CA1 region was increased after pilocarpine-induced seizure. Treadmill exercise inhibited hippocampal neuronal loss in the epileptic rats. Glutamic acid decarboxylase (GAD67) expression in the hippocampal CA1 region was reduced by pilocarpine-induced seizure. Treadmill exercise increased GAD67 expression in the epileptic rats. c-Fos expression in the hippocampal CA1 region was increased in response to epileptic seizure. Treadmill exercise inhibited c-Fos expression in the epileptic rats. Epileptic seizure increased brain-derived neurotrophic factor (BDNF) and tyrosine kinase receptor B (TrkB) expressions in the hippocampus. Treadmill exercise suppressed BDNF and TrkB expressions in the epileptic rats. In the present study...

Tai chi mind-body exercise in patients with COPD: study protocol for a randomized controlled trial

Yeh, Gloria Y; Wayne, Peter M; Litrownik, Daniel; Roberts, David H; Davis, Roger B; Moy, Marilyn L
Fonte: BioMed Central Publicador: BioMed Central
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
36.54%
Background: Chronic obstructive pulmonary disease (COPD) is a chronic, progressively debilitating condition that is prevalent in the US and worldwide. Patients suffer from progressive dyspnea and exercise intolerance. Physical exercise is beneficial, but conventional pulmonary rehabilitation programs are underutilized. There remains a need for novel interventions that improve symptoms, quality-of-life, and functional capacity. Tai chi is an increasingly popular mind-body exercise that includes physical exercise, breathing training, mindful awareness, and stress management--components that are essential to the self-management of COPD. There are, however, limited data on the effectiveness of tai chi as a therapeutic intervention in this population. Methods/Design The Primary Aims are to evaluate the efficacy, safety, and feasibility of a 12-week tai chi program for patients with COPD. We utilize a randomized controlled trial design, with participants assigned in a 2:1 ratio to either a group tai chi program (N = 63) or a time/attention-matched education control (N = 31). Our primary outcomes are COPD-specific quality-of-life and exercise capacity. Secondary outcomes include dyspnea, mood, functional status, self-efficacy, and lung function. Cardiopulmonary exercise testing is done in a subset of patients (N = 50). To explore optimal training duration...

Reduced plasma free fatty acid availability during exercise: effect on gene expression

Tunstall, R.; McAinch, A.; Hargreaves, M.; van Loon, L.; Cameron-Smith, D.
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em //2007 Português
Relevância na Pesquisa
36.54%
Endurance exercise transiently increases the mRNA of key regulatory proteins involved in skeletal muscle metabolism. During prolonged exercise and subsequent recovery, circulating plasma fatty acid (FA) concentrations are elevated. The present study therefore aimed to determine the sensitivity of key metabolic genes to FA exposure, assessed in vitro using L6 myocytes and secondly, to measure the expression of these same set of genes in vivo, following a single exercise bout when the post-exercise rise in plasma FA is abolished by acipimox. Initial studies using L6 myotubes demonstrated dose responsive sensitivity for both PDK4 and PGC-1α mRNA to acute FA exposure in vitro. Nine active males performed two trials consisting of 2 h exercise, followed by 2 h of recovery. In one trial, plasma FA availability was reduced by the administration of acipimox (LFA), a pharmacological inhibitor of adipose tissue lipolysis, and in the second trial a placebo was provided (CON). During the exercise bout and during recovery, the rise in plasma FA and glycerol was abolished by acipimox treatment. Following exercise the mRNA abundance of PDK4 and PGC-1α were elevated and unaffected by either acipimox or placebo. Further analysis of skeletal muscle gene expression demonstrated that the CPT I gene was suppressed in both trials...

Effect of cocoa flavanols and exercise on cardiometabolic risk factors in overweight and obese subjects

Davison, K.; Coates, A.; Buckley, J.; Howe, P.
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em //2008 Português
Relevância na Pesquisa
36.54%
Objective: Impaired endothelial function in obesity may reduce blood flow to sites of metabolism, contributing to impaired fat oxidation and insulin resistance. This study investigated the effects of cocoa flavanols and regular exercise, interventions known to improve endothelial function, on cardiometabolic function and body composition in obese individuals. Design: Overweight and obese adults were randomly assigned to high-flavanol cocoa (HF, 902 mg flavanols), HF and exercise, low-flavanol cocoa (LF, 36 mg flavanols), or LF and exercise for 12 weeks (exercise duration was 3 times 45 min per week at 75% of age-predicted maximum heart rate). Body composition was assessed by dual-energy X-ray absorptiometry at 0 and 12 weeks. Brachial artery flow-mediated dilatation (FMD), supine blood pressure (BP) and fasting plasma insulin, and glucose levels were assessed at 0, 6 and 12 weeks, respectively. Insulin sensitivity/resistance was determined using the modified homeostasis model assessment of insulin resistance (HOMA2). Results: A total of 49 subjects (M=18; F=31) completed the intervention. Baseline averages were as follows: body mass index=33.5 kg/m2; BP=123/76 mm Hg; HOMA2=2.4; FMD=4.3%; rate of fat oxidation during exercise=0.34 g min-1; abdominal fat=45.7% of total abdominal mass. Compared to LF...

Low-frequency fatigue and neuromuscular performance after exercise-induced damage to elbow flexor muscles.

Dundon, J.; Cirillo, J.; Semmler, J.
Fonte: Amer Physiological Soc Publicador: Amer Physiological Soc
Tipo: Artigo de Revista Científica
Publicado em //2008 Português
Relevância na Pesquisa
36.54%
The purpose of this study was to quantify the association between low-frequency fatigue (LFF) and the increase in EMG and force fluctuations after eccentric exercise of elbow flexor muscles. Ten subjects performed two tasks involving voluntary isometric contractions of elbow flexors: a maximum voluntary contraction (MVC) and a constant-force task at five submaximal target forces (5, 10, 20, 40, 60% MVC) while EMG was recorded from biceps and triceps brachii. A third task involved electrical stimulation of biceps brachii at 12 frequencies (1-100 Hz). These tasks were performed before, after, and 2 h and 24 h after concentric or eccentric exercise. MVC force declined after eccentric exercise (34% decline) and remained depressed 24 h later (22% decline), whereas the reduced force following concentric exercise (32%) was recovered 2 h later. Biceps brachii EMG and force fluctuations during the submaximal voluntary contractions increased after eccentric exercise (both approximately 2x greater) with the greatest effect at low forces. LFF was equivalent immediately after both types of exercise (50-60% reduction in 20:100 Hz force) with a slower recovery following eccentric exercise. A significant association was found between the change in LFF and EMG (r(2) values up to 0.52)...

Motor Unit Synchronization is Increased in Biceps Brachii after Exercise-Induced Damage to Elbow Flexor Muscles

Dartnall, T.; Nordstrom, M.; Semmler, J.
Fonte: Amer Physiological Soc Publicador: Amer Physiological Soc
Tipo: Artigo de Revista Científica
Publicado em //2008 Português
Relevância na Pesquisa
36.54%
The purpose of this study was to determine the effect of eccentric exercise on correlated motor unit discharge (motor unit synchronization and coherence) during low-force contractions of the human biceps brachii muscle. Eight subjects (age, 25 ± 7 yr) performed three tasks involving isometric contraction of elbow flexors while EMG (surface and intramuscular) records were obtained from biceps brachii. Tasks were 1) maximum voluntary contraction (MVC); 2) constant-force contraction at various submaximal targets; and 3) sustained discharge of pairs of concurrently active motor units for 2–5 min. These tasks were performed before, immediately after, and 24 h after fatiguing eccentric exercise. MVC force declined 46% immediately after eccentric exercise and remained depressed (31%) 24 h later, which is indicative of muscle damage. For the constant-force task, biceps brachii EMG (~100% greater) and force fluctuations (~75% greater) increased immediately after exercise, and both recovered by ~50% 24 h later. Motor unit synchronization, quantified by cross-correlation of motor unit pairs during low-force (1–26% MVC) contractions, was 30% greater immediately after (n = 105 pairs) and 24 h after exercise (n = 92 pairs) compared with before exercise (n = 99 pairs). Similarly...

Effects of a low carbohydrate weight loss diet on exercise capacity and tolerance in obese subjects

Brinkworth, G.; Noakes, M.; Clifton, P.; Buckley, J.
Fonte: North Amer Assoc Study Obesity Publicador: North Amer Assoc Study Obesity
Tipo: Artigo de Revista Científica
Publicado em //2009 Português
Relevância na Pesquisa
36.54%
Dietary restriction and increased physical activity are recommended for obesity treatment. Very low carbohydrate diets are used to promote weight loss, but their effects on physical function and exercise tolerance in overweight and obese individuals are largely unknown. The aim of this study was to compare the effects of a very low carbohydrate, high fat (LC) diet with a conventional high carbohydrate, low fat (HC) diet on aerobic capacity, fuel utilization during submaximal exercise, perceived exercise effort (RPE) and muscle strength. Sixty subjects (age: 49.2+/-1.2 years; BMI: 33.6+/-0.5 kg/m2) were randomly assigned to an energy restricted (approximately 6-7 MJ, 30% deficit), planned isocaloric LC or HC for 8 weeks. At baseline and week 8, subjects performed incremental treadmill exercise to exhaustion and handgrip and isometric knee extensor strength were assessed. Weight loss was greater in LC compared with HC (8.4+/-0.4% and 6.7+/-0.5%, respectively; P=0.01 time x diet). Peak oxygen uptake and heart rate were unchanged in both groups (P>0.17). Fat oxidation increased during submaximal exercise in LC but not HC (P<0.001 time x diet effect). On both diets, perception of effort during submaximal exercise and handgrip strength decreased (P

Effects of exercise and cocoa flavanol supplementation on cardiometabolic function.

Davison, Kade
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2010 Português
Relevância na Pesquisa
36.54%
The link between excess adipose tissue and an increased risk of developing various pathologies, including cardiovascular (CV) diseases and type 2 diabetes, is now well accepted. There is increasing evidence supporting impaired arterial function (AF) as a causal link in this process. It can therefore be postulated that interventions aimed at improving AF may attenuate or prevent this progression from overweight/obesity to CV and metabolic disease. Exercise has been shown to improve AF in various pathologies. A limitation in the evidence for exercise or increased fitness in an obese population is the differentiation of effects of obesity and fitness or exercise on CV function and risk. To investigate this, a cross sectional study was done to compare cardiorespiratory fitness (CRF; predicted VO₂max) and markers of AF (brachial flow mediated dilatation (FMD), arterial compliance (AC) and blood pressure (BP)) in sedentary obese (N=27) and sedentary lean (N=26) volunteers. The obese group had more whole body fat and abdominal fat (43.5 ± 1.2% vs. 27.2 ± 1.6%; p<0.001 and 48.6 ± 0.9% vs. 28.9 ± 1.8%; p<0.001 respectively) and lower FMD (3.2 ± 0.4% vs. 5.7 ± 0.7%; p<0.01) than the lean subjects but there was no difference in AC. FMD correlated with whole body fat (R = 0.28; p<0.05) and abdominal fat (R = 0.34; p<0.05) but not with CRF. By comparison AC in large arteries was positively associated with CRF (R = 0.5; p<0.01) but not with fatness. These results suggest a differential influence of fitness and fatness on AF. Flavanols from cocoa have been shown to positively influence AF in a variety of CV risk groups...

Bedeutung der Belastungsechokardiographie als zusätzliches Untersuchungsverfahren bei Aortenisthmusstenosen im Kindesalter; The importance of exercise stress echocardiography as an additional examination technique in the case of coarctation of the aorta in childhood

Holzäpfel, Christoph
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
Português
Relevância na Pesquisa
36.54%
Einleitung: Bei grenzwertigen Restenosen nach operativer oder interventioneller Therapie einer Aortenisthmusstenose (ISTA) ist die Indikation zur weiteren Diagnostik und Therapie nicht immer einfach zu stellen. Der Stellenwert der Belastungsechokardiographie im Kindesalter sollte untersucht werden. Methodik: Im Zeitraum von April 2000 bis Dezember 2001 wurden 31 Patienten nach operativer Korrektur einer Aortenisthmusstenose auf einem Liegefahrradergometer mit Steigerung des Pedalwiderstands um 0,5 Watt/kg Körpergewicht alle 2 min bis zur subjektiven körperlichen Erschöpfung belastet (Gruppe 1). Die echokardiographischen Daten wurden mit vorhandenen Magnetresonanztomographie- und Herzkatheterdaten korreliert. Bei 5 dieser Patienten erfolgte eine invasive Therapie und im Abstand von 3 Monaten eine erneute Belastungsechokardiographie (Gruppe 3). Zusätzlich wurden 19 herzgesunde Personen als Kontrollgruppe (Gruppe 2) untersucht. Ergebnisse: Die Flussgeschwindigkeit in der Aorta descendens unterscheidet sich bereits in Ruhe zwischen Gruppe 1 (2,66 ± 0,56 m/s) und der Kontrollgruppe (1,5 ± 0,17 m/s) signifikant. Der systolische Blutdruck ist in Ruhe in der Gruppe 1 und 2 im Mittel gleich. Der Blutdruckgradient zwischen den oberen und unteren Extremitäten ist in der Gruppe 2 mit –21 mmHg deutlich größer als in der Gruppe 1 (Mittelwert –1). Bei maximaler Belastung steigt die Flussgeschwindigkeit in der Aorta descendens in beiden Gruppen an (3...

Messung des Atemgasflow unter Laufbandbelastung als diagnostisches Verfahren bei Belastungsasthma (EIA); Determination of the flow of respiratory gases under treadmill ergometer exertion as diagnosis for exercise-induced asthma (EIA)

Wolters, Roman
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
Português
Relevância na Pesquisa
36.54%
"Belastungsasthma", im angloamerikanischen auch als "exercise-induced asthma (EIA)" oder "exercise-induced bronchoconstriction (EIB)" bezeichnet, ist mit einer Prävalenz von 4-20% der Normalbevölkerung und 10-50% unter Sportlern eine weit verbreitete Erkrankung. Die Diagnosestellung des EIA bereitet immer noch Probleme, da sich bis dato bei allen gängigen Testverfahren die Bronchokonstriktion mit der auslösenden Belastung nur indirekt in Zusammenhang bringen lässt, d.h. der Nachweis der Bronchokonstriktion gelingt entweder erst nach der Belastung oder es wird gar nicht die Belastung selbst simuliert sondern ein anderer auslösender Faktor (medikamentöse Provakationstests). Zudem ist der Nachweis einer Bronchokonstriktion mittels eines Lungenfunktionstests immer von der Motivation der zu untersuchenden Person abhängig. Ziel der vorliegenden Arbeit war es, die Bronchokonstriktion zum Zeitpunkt ihrer Entstehung mittels Lungenfunktionsdiagnostik noch während einer hochintensiven Ausdauerbelastung nachzuweisen und somit ein objektives Diagnoseverfahren für EIA zu entwickeln. Hierfür wurde eine Personengruppe (n=10) mit vordiagnostiziertem Belastungsasthma, sowie eine Kontrollgruppe (n=10) einem hochintensiven Ausdauerbelastungstest unterzogen. Dabei wurden vor und nach der Belastung Lungenfunktionstests mit Bestimmung der Einsekundenkapazität (FEV1) durchgeführt. Während der Ausdauerbelastung wurde die Atemstromgeschwindigkeit kontinuierlich aufgezeichnet. Die Ergebnisse der vorliegenden Arbeit können wie folgt zusammengefasst werden: - Die Verringerung des exspiratorischen Peakflow zu 80 und 93% einer erschöpfenden hochintensiven Ausdauerbelastung um mehr als 3% stimmt signifikant mit einer Verringerung des FEV1 um >10% vor und nach Belastung überein und kann somit als Grundlage eines neues...