A densidade como uma nova métrica da quantificação de cargas no treinamento de força / Density as a new metric to quantify strength training loads

O objetivo do estudo foi realizar um breve comunicado sobre a adoção da densidade com uma nova métrica de quantificação de cargas no treinamento de força. Descrevemos como quantificá-la e destacamos as possíveis implicações da sua manipulação. Uma vez que considera o intervalo de recuperação entre as séries - onde podem ocorrer processos metabólicos importantes, como a ressíntese de fosfocreatina - a densidade pode ser um parâmetro representativo da magnitude do estresse metabólico induzido pelas sessões. Recomendamos que treinadores e pesquisadores da área de ciências do esporte passem a reportar quantificar e reportar a densidade dos treinos. Técnicas de treinamento que manipulam as pausas entre as séries, repetições e exercícios, como os treinos em circuito, o restpause, cluster training, intra-set rest e/ou inter-repetion rest, podem ter novas análises e, consequentemente, resultados interessantes a serem reportados.(AU)

The aim of the study was to provide a short communication about the adoption of density as a new metric to quantify strength training loads. We describe how quantify and highlighted the possible implications of density manipulation. Since considers the rest interval between sets - where important metabolic process such as phosphocreatine resynthesizes may occurs ­ density may represent the magnitude of metabolic stress induced by training session. In this sense, is recommended that sports sciences coach's and researchers report the training density. Training techniques that manipulate the rest intervals between sets, repetitions, and exercises, such as circuit tra ining, rest pause, cluster training, intra-set rest, and/or inter-repetition rest may have new analysis, and consequently interesting results to be reported.(AU)

Comparação do número máximo de repetições em séries múltiplas entre indivíduos com diferentes tempos de experiência no treinamento de força / Comparison of the maximum number of repetitions in multiple series between individuals with different times of experience in resistance training

O treinamento de força (TF) proporciona adaptações centrais e morfológicas que influenciam no processo de produção de força. Em função destas adaptações é esperado que ocorram diferenças no desempenho de força entre homens com diferentes tempos de experiência no TF quanto testados em séries múltiplas. Assim, este estudo teve como objetivo comparar o número máximo de repetições (NMR) realizadas em 3 séries entre indivíduos com diferentes tempos de experiência no TF. Para isso, vinte e dois homens foram divididos em dois grupos de acordo com o tempo de experiência no TF. O Grupo Muito Experiente (GME) foi representado por homens com mais de 5 anos no TF. O Grupo Pouco Experiente (GPE) foi composto por homens com 1 a 6 meses de experiência no TF. Os grupos foram submetidos à realização do maior número de repetições em três séries a 80% de 1RM no exercício supino reto. Além disso, a duração média da repetição (DMR) foi registrada e comparada em cada série intra e inter grupos. Para as comparações foram utilizadas duas ANOVAs com única variável (NMR ou DMR) e dois fatores (fator 1 = experiência, fator 2 = série). Na análise do NMR foi detectada uma interação entre os fatores, sendo que o número máximo de repetições realizado pelo GME foi maior do que o GPE apenas na primeira série (p = 0,017). Quanto à DMR, não foram encontradas diferenças entre os grupos (p = 0,80) e séries (p= 0,06). Conclui-se que o tempo de experiência no TF interferiu na realização do número máximo de repetições apenas na primeira série... (AU)

Strength training (TF) provides central and morphological adaptations that influence the process of force production. Due to these adaptations, it is expected that differences in force performance occurred between men with different times of experience in the TF when tested in multiple series. Thus, this study had as objective to compare the maximum number of repetitions (NMR) performed in 3 sets between individuals with different times of experience in the TF. For this, twenty-two men were split into two groups according to the time of experience in the TF. The Very Experienced Group (GME) was represented by men older with at least 5 years in TF. The Little Experienced Group (GPE) was composed of men with 1 to 6 months of experience in TF. The groups were submitted to perform the highest number of repetitions in three sets at 80% of 1RM in the bench press exercise. In addition, mean repetition duration (DMR) was recorded and compared in each set and group. For the comparison, two ANOVAs with a single variable (NMR or DMR) and two factors (factor 1 = experience, factor 2 = set) were used. In the NMR analysis, an interaction between the factors was detected, and the NMR performed by the GME was higher than the GPE only at the first set (p = 0.017). Regarding DMR, no differences were found between groups (p = 0.80) and sets (p = 0,06). It is concluded that the time of experience in the TF interfered in the Performance of the maximum number of repetitions only at the first set...(AU)

Efficacy of phosphocreatine pre-administration on XIAP and Smac in ischemic penumbra of rats with focal cerebral ischemia reperfusion injury

Abstract Purpose: To observe the efficacy of phosphocreatine pre-administration (PCr-PA) on X-linked inhibitor of apoptosis protein (XIAP), the second mitochondia-derived activator of caspase (Smac) and apoptosis in the ischemic penumbra of rats with focal cerebral ischemia-reperfusion injury (CIRI). Methods: A total of 60 healthy male Sprague Dawley (SD) rats were randomly divided into three groups (n=20): group A (the sham operation group), group B <intraperitoneally injected with 20 mg/kg (10 mg/ml) of saline before preparing the ischemia-reperfusion (IR) model>, and group C <intraperitoneally injected with 20 mg/kg (10 mg/ml) of PCr immediately before preparing the IR model>. After 24 h for reperfusion, the neurological function was evaluated and the tissue was sampled to detect expression of XIAP, Smac and caspase-3 positive cells in the ischemic penumbra so as to observe the apoptosis. Results: Compared with group B, neurological deficit scores, numbers of apoptotic cells, expression of Smac,caspase-9 and the numbers of Caspase-3 positive cells were decreased while expression of XIAP were increased in the ischemic penumbra of group C. Conclusions: Phosphocreatine pre-administration may elicit neuroprotective effects in the brain by increasing expression of X-linked inhibitor of apoptosis protein, reducing expression of second mitochondia-derived activator of caspase, and inhibiting the apoptosis in the ischemic penumbra.

Skeletal Muscle Glycogen Breakdown According to Duration of Endurance Training / 대한스포츠의학회지

Endurance exercise training such as marathon can increase the ability of exercise performance. Muscle glycogen is associated with an exercise performance, because glycogen depletion is primary causes of muscle fatigue. This review summarizes the glycogen saving effect according to duration of endurance exercise training. Long-term endurance exercise-induced mitochondrial biogenesis contributes to glycogen saving effect that is reduced glycogen breakdown and lactate accumulation. Glycogen sparing is due to a smaller decrease in adenosine triphosphate and phosphocreatine and a smaller increase in inorganic phosphate in the working muscles. It takes required endurance exercise training for about 4 weeks or more. Single bout or short-term endurance exercise is not sufficient to bring an increase in functional mitochondria. But peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) increases rapidly after single bout of endurance exercise. PGC-1α downregulates glycogenolytic and glycolytic enzymes to reduce muscle glycogen breakdown and lactic acid accumulation after short-term endurance exercise.

Role of the phosphocreatine system on energetic homeostasis in skeletal and cardiac muscles / Papel do sistema da fosfocreatina na homeostase energética das musculaturas esquelética e cardíaca

Adenosine triphosphate is the present energy currency in the body, and is used in various cellular and indispensable processes for the maintenance of cell homeostasis. The regeneration mechanisms of adenosine triphosphate, from the product of its hydrolysis – adenosine diphosphate – are therefore necessary. Phosphocreatine is known as its quickest form of regeneration, by means of the enzyme creatine kinase. Thus, the primary function of this system is to act as a temporal energy buffer. Nevertheless, over the years, several other functions were attributed to phosphocreatine. This occurs as various isoforms of creatine kinase isoforms have been identified with a distinct subcellular location and functionally coupled with the sites that generate and use energy, in the mitochondria and cytosol, respectively. The present study discussed the central and complex role that the phosphocreatine system performs in energy homeostasis in muscle cells, as well as its alterations in pathological conditions.

A adenosina trifosfato é a moeda corrente de energia no organismo, sendo utilizada em diversos processos celulares e indispensável para a manutenção da homeostase celular. Mecanismos de regeneração da adenosina trifosfato, a partir de seu produto de hidrólise – a adenosina difosfato – são, dessa forma, necessários. A fosfocreatina é conhecidamente sua fonte mais rápida de regeneração, por meio da enzima creatina quinase. Assim, a principal função desse sistema é atuar como um tampão temporal de energia. Entretanto, ao longo dos anos, diversas outras funções foram atribuídas à fosfocreatina. Isso ocorreu à medida que foram identificadas diversas isoformas da creatina quinase com localização subcelular distinta e acopladas de forma funcional aos sítios geradores e utilizadores de energia, na mitocôndria e citosol, respectivamente. O presente trabalho discutiu o papel central e complexo que o sistema da fosfocreatina desempenha na homeostase energética nas células musculares, bem como suas alterações em quadros patológicos.

Thalamic metabolic abnormalities in patients with Huntington's disease measured by magnetic resonance spectroscopy

Huntington's disease (HD) is a neurologic disorder that is not completely understood; its fundamental physiological mechanisms and chemical effects remain somewhat unclear. Among these uncertainties, we can highlight information about the concentrations of brain metabolites, which have been widely discussed. Concentration differences in affected, compared to healthy, individuals could lead to the development of useful tools for evaluating the progression of disease, or to the advance of investigations of different/alternative treatments. The aim of this study was to compare the thalamic concentration of metabolites in HD patients and healthy individuals using magnetic resonance spectroscopy. We used a 2.0-Tesla magnetic field, repetition time of 1500 ms, and echo time of 135 ms. Spectra from 40 adult HD patients and 26 control subjects were compared. Quantitative analysis was performed using the LCModel method. There were statistically significant differences between HD patients and controls in the concentrations of N-acetylaspartate+N-acetylaspartylglutamate (NAA+NAAG; t-test, P<0.001), and glycerophosphocholine+phosphocholine (GPC+PCh; t-test, P=0.001) relative to creatine+phosphocreatine (Cr+PCr). The NAA+NAAG/Cr+PCr ratio was decreased by 9% and GPC+PCh/Cr+PCr increased by 17% in patients compared with controls. There were no correlations between the concentration ratios and clinical features. Although these results could be caused by T1 and T2 changes, rather than variations in metabolite concentrations given the short repetition time and long echo time values used, our findings point to thalamic dysfunction, corroborating prior evidence.

Treatment of myocardial damage with creatine phosphate following neonatal asphyxia: a meta-analysis / 中国当代儿科杂志

<p><b>OBJECTIVE</b>To evaluate the effects of creatine phosphate (CP) in the treatment of myocardial damage following neonatal asphyxia.</p><p><b>METHODS</b>Medical databases were searched for a systematic literature review and meta-analysis of randomized and quasi-randomized trials on the treatment of myocardial damage with CP following neonatal asphyxia. The data was analyzed using Review Manager 5.1.</p><p><b>RESULTS</b>Six trials involving 400 patients (CP treatment/control: 202/198) were included in the survey. The meta-analysis indicated that CP treatment for 7 days decreased serum myocardial enzyme levels (CK, CK-MB, LDH, HBDH and cTnI levels). Both the total effective rate (RR: 1.29; 95% CI: 1.12, 1.48) and the significantly effective rate (RR: 1.78; 95% CI: 1.32, 2.41) in the CP treatment group were significantly higher than in the control group. CP treatment reduced the hospitalization period by 4.07 days compared with the control group (95% CI: -5.25, -2.89).</p><p><b>CONCLUSIONS</b>CP treatment appears to be more effective than routine treatment alone for myocardial damage following neonatal asphyxia. It appears to be safe and it can both decrease serum myocardial enzyme levels and shorten the period of hospitalization. However, as the evidence obtained in this study is not robust due to the poor quality of current studies, further studies of high-quality, large-scale trails are needed.</p>

Value of dynamic ³¹P magnetic resonance spectroscopy technique in in vivo assessment of the skeletal muscle mitochondrial function in type 2 diabetes / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Phosphorous magnetic resonance spectroscopy ((31)P-MRS) has been successfully applied to study intracellular membrane compounds and high-energy phosphate metabolism. This study aimed to evaluate the capability of dynamic (31)P-MRS for assessing energy metabolism and mitochondrial function in skeletal muscle from type 2 diabetic patients.</p><p><b>METHODS</b>Dynamic (31)P-MRS was performed on 22 patients with type 2 diabetes and 26 healthy volunteers. Spectra were acquired from quadriceps muscle while subjects were in a state of rest, at exercise and during recovery. The peak areas of inorganic phosphate (Pi), phosphocreatine (PCr), and adenosine triphosphate (ATP) were measured. The concentration of adenosine diphosphate (ADP) and the intracellular pH value were calculated from the biochemistry reaction equilibrium. The time constant and recovery rates of Pi, PCr, and ADP were analyzed using exponential curve fitting.</p><p><b>RESULTS</b>As compared to healthy controls, type 2 diabetes patients had significantly lower skeletal muscle concentrations of Pi, PCr and β-ATP, and higher levels of ADP and Pi/PCr. During exercise, diabetics experienced a significant Pi peak increase and PCr peak decrease, and once the exercise was completed both Pi and PCr peaks returned to resting levels. Quantitatively, the mean recovery rates of Pi and PCr in diabetes patients were (10.74 ± 1.26) mmol/s and (4.74 ± 2.36) mmol/s, respectively, which was significantly higher than in controls.</p><p><b>CONCLUSIONS</b>Non-invasive quantitative (31)P-MRS is able to detect energy metabolism inefficiency and mitochondrial function impairment in skeletal muscle of type 2 diabetics.</p>

Pharmacokinetics and metabolic disposition of exogenous phosphocreatine in rats / 药学学报

This article is report the study of the pharmacokinetics and metabolic disposition of exogenous phosphocreatine (PCr) in rats by means of an ion-pair HPLC-UV assay. PCr and its metabolite creatine (Cr) and related-ATP in rat plasma and red blood cell (RBC) were simultaneously determined. A blank plasma and RBC were initially run for baseline subtraction. Plasma and RBC samples were deproteinized with 6% PCA prior to HPLC. Following i.v. administration of PCr 500 mg x kg(-1) and 1 000 mg x kg(-1) the C-T curve could be described by the two-compartment model with t1/2beta 22.5-23.3 min, V(d) 0.956 4-0.978 6 L x kg(-1), CL 0.029 L. kg(-1) x min(-1). The Cr as PCr degraded product appeared as early as 2 min post i.v. dosing with t(max) 20 min, t1/2kappa (m) 40.6-42.7 min and f(m) 60%-76%. After po administration of PCr, the parent drug in plasma was undetectable, but the metabolite Cr was detected with t(max) 65-95 min, t1/2kappa (m) 56.0-57.7 min, metabolite-based bioavailability F(m) 55.02%-62.31%. PCr i.v. administration resulted in significant elevation of ATP level in RBC but not in plasma, the related-ATP in RBC was characterized by t(max) 68-83 min, t1/2kappa 49-52 min. In RBC no exogenous PCr was found but Cr was detected following i.v. administration of PCr, with the t(max) 120 min and t1/2k (m) 70 min for Cr. The above results indicate that PCr eliminates and bio-transforms in body very rapidly; K > K(m) confers ERL, instead of FRL, type upon the metabolic disposition of Cr. Following po administration of PCr, the degraded product Cr is absorbed but not the parent drug PCr. The formed Cr can be accounted for by most of i.v. and po PCr. Intravenous dosing leads apparently increased and sustained Cr and related-ATP concentration in RBC.

Prevalencia de alteraciones de la creatina-fosfoquinasa (CPK) sérica en pacientes que toman estatinas / Prevalence of abnormalities of creatine phosphokinase (CPK) levels in patients taking statins

El uso de estatinas para combatir la dislipidemia se asocia con un espectro de síntomas musculares que van desde mialgias con o sin aumento de la creatina-fosfoquinasa (CPK), hasta rabdomiólisis fatal. Objetivo: determinar la prevalencia de la elevación de la CPK en pacientes que toman estatinas y determinar los posibles factores de riesgo asociados al aumento de la CPK en estos pacientes. Métodos: estudio observacional de corte transversal en el que se evaluaron las alteraciones de la CPK en una población de 503 pacientes con tratamiento con estatinas para el control de la dislipidemia, y que asisten al Laboratorio Clínico Hematológico en Medellín, Colombia por razones diferentes a la medición de la CPK. Mediante un cuestionario aplicado a los pacientes se obtuvieron los datos demográficos, los antecedentes personales y el tipo de estatina utilizada. Resultados: 56 (11,1 por ciento) pacientes presentaron aumento de la CPK por encima del rango de referencia normal; 7 pacientes (1,4 por ciento) tenían un aumento dos veces por encima del valor superior normal, y de ellos 3 (0,6 por ciento) tenían un aumento tres veces por encima del valor superior normal. Se encontró asociación significativa entre niveles altos de la CPK con el sexo masculino y con el uso de inhibidores selectivos de la recaptación de serotonina (ISRS). No se encontró asociación con otros factores de riesgo previamente descritos en otros estudios como son el ejercicio, el consumo de alcohol, el hipotiroidismo y la dosis de estatinas, entre otros. En cuanto a síntomas musculares, el 28,4 por ciento relató dolor muscular con el uso de estatinas, 26 por ciento cansancio y 15,9 por ciento debilidad muscular. Conclusión: los hallazgos de este estudio demuestran que el aumento asintomático de la CPK en pacientes que toman estatinas para la reducción por ciento del colesterol, es mayor al previamente reportado y confirma que el sexo masculino y el uso de fármacos tipo ISRS se relacionan con un aumento de la CPK. También se encontró que el porcentaje de pacientes con síntomas musculares, especialmente dolor y cansancio, es mucho mayor a lo reportado en la literatura mundial. Desde el punto de vista clínico se desconocen las repercusiones que pueda tener el aumento asintomático de la CPK, lo que requeriría estudios de seguimiento a largo plazo.

A preliminary study on the effects of the exogenous creatine phosphate on rat masseter muscle after unilateral chew / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To study the effect of energy therapy on Ca2+ concentration and Ca2+ -ATP enzyme activity in rat master muscle after unilateral chew, and to discuss the protective action of the exogenous creatine phosphate on rat masseter muscle after unilateral chew.</p><p><b>METHODS</b>The 20 rats were randomly divided into 4 groups, A: Creatine phosphate normal control group; B: Creatine phosphate experimental group; C: Saline normal control group; D: Saline experimental group. The Ca2+ concentration were determined by atomic absorption spectrophotometry, the activity of the Ca2+ -ATP enzyme were determined by super-micro volume Ca2+ -ATP enzyme kit.</p><p><b>RESULTS</b>(1) The Ca2+ concentration of the extraction side of group D which received the saline injection had significant difference compared with the non-extraction side (P = 0.007), the group C (P = 0.009) and the extraction side of group B (P = 0.01); (2) Ca2+ -ATP enzyme activity of group D were higher than its non-extraction side (P = 0.001), group C (P = 0.003) and the extraction side of group B (P = 0.001); (3) The ultrastructural changes of the rat masseter muscle under transmission electron microscope were as follows: The extraction side of group D have more severe pathological manifestations than non-extraction side. Both the extraction side and the non-extraction side of group B had a similar manifestation to the normal control group.</p><p><b>CONCLUSION</b>Exogenous energy material, creatine phosphate, may have certain degree of protective effect on rat masseter muscles after unilateral chew. And it may become a possible way to improve the injury of the masseter muscle.</p>

Clinical application of proton magnetic resonance spectroscopy in children with idiopathic epilepsy / 中国当代儿科杂志

<p><b>OBJECTIVE</b>This study examined the biochemical metabolism by proton magnetic resonance spectroscopy ('H-MRS) in order to explore the value of 'H-MRS in idiopathic epilepsy in children.</p><p><b>METHODS</b>Thirty-three children with idiopathic epilepsy (14 cases with history of febrile seizures and 19 cases without) and six normal controls experienced MRI of the skull and brain and single-voxel 'H-MRS examinations of the hippocampi-temporal lobe. The signal intensities of N-acetylaspartate (NAA), eatine+phosphocreatine (Cr), choline-containing compounds (Cho) and lactate (Lac) and the ratios of NAA/ (Cho+Cr) and Lac/Cr were compared between the patients and normal controls.</p><p><b>RESULTS</b>MRI examination showed that only one child with epilepsy had myelin dysplasia. 'H-MRS examination showed that the ratio of NAA/ (Cho+Cr) in the epilepsy group was lower than that in the control group (0.64+/-0.07 vs 0.73+/-0.05; P<0.01). The epileptic children with history of febrile seizures had a more decreased ratio of NAA/ (Cho+Cr) compared with those without the history (0.61+/-0.07 vs 0.66+/-0.06; P<0.05). There were no significant differences in the ratio of Lac/Cr between the epilepsy and the control groups.</p><p><b>CONCLUSIONS</b>'H-MRS may provide early information on brain injury sensitively and non-invasively in children with epilepsy. It may be used for diagnosis and prognosis evaluation of epilepsy.</p>

Effects of phosphocreatine on plasma brain natriuretic peptide level in elderly patients with chronic congestive heart failure / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the therapeutic effects of phosphocreatine in elderly patients with chronic congestive heart failure (CHF) and its effects on plasma brain natriuretic peptide (BNP).</p><p><b>METHODS</b>Forty elderly patients with chronic CHF were randomly divided into two groups to receive basic treatment (control group) and additional phosphocreatine treatment (treatment group) with a treatment course of 8 weeks. The patients were evaluated for improvement in New York Heart Association (NYHA) functional class, symptoms, left ventricular end-diastolic diameter (LVEDD), left ventricular end-systolic diameter (LVESD), and left ventricular ejection fraction (LVEF) and the levels of BNP before and after treatment.</p><p><b>RESULTS</b>After 8 weeks of treatment, the overall efficacy rate was significantly higher in treatment group than in the control group, and LVESD, LVEDD, LVEF and BNP level of the treatment group were significantly lowered in comparison with those of the control group (P<0.05).</p><p><b>CONCLUSION</b>Phosphocreatine in addition to the basic treatment can reduce the BNP level and improve the cardiac systolic and diastolic function in elderly patients with chronic CHF.</p>

Changes of 3-tesla 31P-MR spectroscopy of bone and soft tissue tumors / 中华肿瘤杂志

<p><b>OBJECTIVE</b>To study the characteristic changes of 31P-MR spectroscopy of bone and soft tissue tumors.</p><p><b>METHODS</b>41 patients were examined by phosphorus surface coil of 3 tesla MR machine, including 18 benign tumor foci and 28 malignant foci, and adjacent normal muscles. The areas under the peaks of various metabolites in the spectra were measured, including phosphomonoester (PME), inorganic phosphours (Pi), phosphodiester (PDE), phosphocreatine (Pcr), adenosine triphosphate (ATP) gamma, alpha, beta. The ratios of the metabolites to beta-ATP, NTP and Pcr were calculated. Intracellular pH was calculated according to the chemical shift change of Pi relative to Pcr.</p><p><b>RESULTS</b>The ratios of Pcr/PME and PME/NTP in benign and malignant tumor groups were significantly different from those of the normal group (P<0.05). Between benign and malignant tumor groups, the ratios of PME/beta-ATP and PME/NTP were significantly different (P<0.05).</p><p><b>CONCLUSION</b>Pcr/PME and PME/NTP are potential diagnostic indexes of bone and soft tissue tumors. PME/beta-ATP and PME/NTP are potential indexes of differential diagnosis of bone and soft tissue tumors.</p>

Non-invasive assessment of oxidative capacity in young Indian men and women: a 31P magnetic resonance spectroscopy study.

It is generally assumed that men display greater strength and muscle capacity than women. However, previous biochemical and histological studies have shown that men have greater capacity for anaerobic metabolism and women have higher or similar oxidative metabolism. Therefore, in the present study, we estimated oxidative capacity of gastrocnemius muscle and compared in Indian men and women using non-invasive in vivo 31P magnetic resonance spectroscopy (MRS). Healthy subjects (8 young males and 9 females, age-matched) performed plantar flexion exercise within a magnet and MRS measurements of inorganic phosphate (Pi), phosphocreatine (PCr), ADP, and pH of the calf muscles were carried out using a 1.5 T whole-body MRI system. PCr values during recovery were fitted to an exponential curve, and oxidative capacity was calculated using rate constant (k(PCr)), as an index of oxidative phosphorylation. When men and women were compared for different metabolic ratios, ADP, pH, k(PCr) and oxidative capacity, all parameters turned out to be statistically insignificant. The results showed no gender effect on skeletal muscle oxidative metabolism. The study demonstrated the usefulness of such non-invasive method to indirectly measure the oxidative capacity of the muscle based on PCr recovery.

Efeitos da suplementação de creatina no exercício intermitente de alta intensidade: divergências e recomendações metodológicas / Effects of creatine supplementation on high-intensity intermittent exercise: discrepancies and methodological appraisals

Após breve revisão da literatura existente acerca dos efeitos da suplementação de creatina no rendimento ematividades intermitentes de alta intensidade, o objetivo principal dessa revisão foi discutir diferenças metodológicas dos estudos que possam explicar a divergência encontrada na literatura. Os efeitos da suplementação de creatina no exercício intermitente de alta intensidade são bastante investigados. Embora existam inúmeros achados demonstrando a eficácia desse suplemento nesse tipo de atividade, outras tantas evidências não suportam tal efeito ergogênico. A explicação para essa divergência parece ser multifatorial, porém sempre ligada às questões metodológicas. O modelo do estudo (crossover ou grupos independentes paralelos), a variabilidade individual no conteúdo muscular de creatina, o alto consumo de carnes, o tamanho da amostra, as características do protocolo de exercício (dependência do peso corporal e tempo de intervalo entre as séries), e diferenças de gênero e idade entre estudos são potenciais variáveis que explicam, em maior ou menor magnitude, a discrepância na literatura. Estudos envolvendo homens jovens, com modelo de grupos paralelos, poder estatístico satisfatório, controle da incorporação de creatina muscular, avaliação do consumo alimentar e protocolos de exercícios intermitentes máximos, cujo rendimento não depende do peso corporal, com intervalos de recuperação entre 1 a 6 minutos, tendem a apresentar resultados positivos. Os diversos fatores metodológicos que podem contribuir para a divergência acerca do tema devem ser considerados quando da realização de futuros estudos, bem como no momento da prescrição desse suplemento...

After a brief review of the literature on the effects of creatine supplementation on high-intensity intermittent exercise performance, the main aim of this study was to discuss methodological differences between studies which could explain the discrepancies observed in the literature. The effects of creatine supplementation on high-intensity intermittent exercise performance have been investigated in depth. Although the results of much research demonstrates the efficacy of this supplement, there is just as much evidence that does not support this ergogenic effect. The explanation for this divergence appears to be multifactorial, although it is always linked to methodological characteristics. Study design (crossover or parallel groups), individual variability of muscular creatine content, chronic high meat intake, sample size, exercise protocol characteristics (body weight dependence and time between series), and gender and age all differ between studies and are potentially the variables responsible, to differing extents, for the discrepancies observed in the literature. Studies involving young males, with parallel group design, adequate statistical power, control of the incorporation of creatine into muscles, food intake assessment and intermittent exercise protocols in which performance is independent of body weight and with rest-recovery intervals of 1 to 6 minutes, usually produce positive results. The many methodological factors which can contribute to divergence on the ergogenic effects of creatine should be considered in futures studies, as well as when prescribing creatine supplementation...

Cerebral metabolites concentrations determined by quantitative proton MR spectroscopy in patients of intracerebral haematomas

This study was made to investigate serial metabolic changes in frontal lobes of patients with deep intracerebral hemorrhage [ICH] to found any correlation between N-acetylaspartate [NAA] and degree of motor impairment or clinical outcome. Forty three patients with deep ICH were examined with proton magnetic resonance spectroscopy by multivoxel method [voxel=10 X 10 X 20 mm; 64 voxels]. NAA/creatine ratios in the white matter of the primary motor and premotor areas on both sides were measured sequentially: within 48 hours, at 2 weeks, and 1 month after onset using National Institutes of Health Stroke Scale We found, in the primary motor area on the affected side, the NAA/ creatine ratio decreased sequentially. At 48 hours and 2 weeks after onset, a negative correlation was detected between NAA/creatine and hematoma volume, but there was no correlation 1 month later. At 2 weeks, NAA/ creatine correlated negatively with motor impairment. In conclusions, there is delayed gradual reduction of NAA/creatine ratio in the frontal lobes correlating with motor deficit and clinical outcome after deep ICH

Estimation of postmortem interval with multivoxel-voxel proton 1H-MR spectroscopy / 法医学杂志

OBJECTIVE@#The purpose of our study was to evaluate the postmortem interval with multi-voxel 1H-MR spectroscopy.@*METHODS@#Twelve healthy rabbits were studied and the quantities of N-acetylaspartate, total choline, phosphocreatine and creatine were measured by 1H-MR spectroscopy after death at 0.5, 1, 2, 4, 6, 8, 12, 16, and 24 h.@*RESULTS@#The levels of Naa/Cr and Naa/Ch decreased following death, while the level of Ch/Cr increased initially and then decreased following death.@*CONCLUSION@#Multi-voxel proton MR spectroscopy for Naa/Cr and Ch/Cr metabolic ratio could be used in future postmortem interval studies.

Parâmetros mecânicos e metabólicos do desempenho em intensidade supra-máxima de nado crawl / Mechanical and metabolic parameters of front crawl swim performance at supramaximal intensity

O objetivo deste estudo foi analisar o desempenho supra-máximo no nado crawl (vmax) pelas relações entre energia anaeróbia (Eanaer), potência muscular (Po) e propulsiva (Pu), eficiência mecânica (emec) e propulsiva (ep), economia e força de arrasto (Fr). Onze competidores submeteram-se à avaliação de Fr pelo método de Perturbação da Velocidade e à estimativa da ep, pelas relações entre Fr e a ação do hidrofólio. Eanaer foi quantificada pelo equivalente energético do lactato e da fosfocreatina. Correlações de vmax com Eanaer (0,71), economia (0,65), Fr (0,68), Pu (0,79) e Po (0,69) sugerem que força, potência e disponibilidade de energia sustentam o desempenho em vmax. Contudo, ao restringir Eanaer em vmax, apenas a economia acomoda-se a esta condição (-0,95), enquanto que emec torna-se determinante para Fr (0,97), Pu (0,90) e Po (0,98). Conclui-se que a taxa de trabalho é decisiva no desempenho supramáximo, e que Eanaer subsidia sua produção, mas quando restrita, emec e economia interagem-se como fatores fundamentais para manter a taxa de trabalho no patamar demandado por esta condição de nado.

The purpose of this study was to analyze crawl performance at supramaximal intensity (vmax) from relationships between anaerobic energy (Eanaer), mechanical and propulsive power (Po, Pu), mechanical and propulsive efficiency (emec, ep), and drag force (Fr). Eleven experience swimmers were undergone to the measurement of Fr from the method of Velocity Perturbation, and to estimative the ep from Fr relationships to hydrofoil action. Eanaer was estimated from lactate and phosphocreatine energy equivalents. Correlations of vmax to Eanaer (0,72), economy (0,65), Fr (0,68), Pu (0,79), and Po (0,69) suggest a trend to force, power and energy release to determine performance at vmax. Once Eanaer became constrained, only economy was able to accommodated to these context (-0,95), whereas emec improve their influence on Fr (0,97), Pu (0,90), and Po (0,98). In conclusion, work rate is the main parameter to ensure supramaximal performance, and Eanaer is the major factor in power availability, but when it is constrained, emec and economy interactions plays a fundamental role to maintain the level of work rate production enough to reach supramaximal swim requirements.