肌肉红白纤维辨析     

于桂林 《湖北体育科技》2013,(12):1060-1062

两类肌纤维LDH同功酶的差别在于不仅能决定它们的代谢方式,且红纤维的LDH可帮助白纤维在运动中产生其本身难以氧化的乳酸。因两类肌纤维肌球蛋白———ATP酶活性的差别,决定它们的收缩速度不同。又由于肌肉具有不同纤维类型相互转化的遗传潜力等,人体在发育中的分化问题和神经纤维类型的分化是否会受一定遗传控制。如果对这些问题都一并加以研究,将有助于更好地揭示两类肌纤维能否转化的问题。  相似文献   

Effect of time-of-day-specific strength training on maximum strength and EMG activity of the leg extensors in men     

Milan Sedliak  Taija Finni  Jussi Peltonen  Keijo Häkkinen 《Journal of sports sciences》2013,31(10):1005-1014

Abstract

In this study, we examined the effects of time-of-day-specific strength training on maximum strength and electromyography (EMG) of the knee extensors in men. After a 10-week preparatory training period (training times 17:00–19:00 h), 27 participants were randomized into a morning (07:00–09:00 h, n = 14) and an evening group (17:00–19.00 h, n = 13). Both groups then underwent 10 weeks of time-of-day-specific training. A matched control group (n = 7) completed all testing but did not train. Unilateral isometric knee extension peak torque (MVC) and one-repetition maximum half-squat were assessed before and after the preparatory training and after the time-of-day-specific training at times that were not training-specific (between 09:00 and 16:00 h). During training-specific hours, peak torque and EMG during MVC and submaximum isometric contraction at 40% MVC were assessed before and after the time-of-day-specific training. The main finding was that a significant diurnal difference (P < 0.01) in peak torque between the 07:00 and 17:00 h tests decreased after time-of-day-specific training in the morning group but not in the evening or control groups. However, the extent of this time-of-day-specific adaptation varied between individuals. Electromyography during MVC did not show any time-of-day-specific adaptation, suggesting that peripheral rather than neural adaptations are the main source of temporal specificity in strength training.  相似文献   

No effect of glutamine supplementation and hyperoxia on oxidative metabolism and performance during high-intensity exercise     

Simon Marwood  Jo Bowtell 《Journal of sports sciences》2013,31(10):1081-1090

Abstract

Glutamine enhances the exercise-induced expansion of the tricarboxylic acid intermediate pool. The aim of the present study was to determine whether oral glutamine, alone or in combination with hyperoxia, influenced oxidative metabolism and cycle time-trial performance. Eight participants consumed either placebo or 0.125 g · kg body mass^?1 of glutamine in 5 ml · kg body mass^?1 placebo 1 h before exercise in normoxic (control and glutamine respectively) or hyperoxic (FiO₂ = 50%; hyperoxia and hyperoxia + glutamine respectively) conditions. Participants then cycled for 6 min at 70% maximal oxygen uptake ([Vdot]O_2max) immediately before completing a brief high-intensity time-trial (～4 min) during which a pre-determined volume of work was completed as fast as possible. The increment in pulmonary oxygen uptake during the performance test (Δ[Vdot]O_2max, P = 0.02) and exercise performance (control: 243 s, s _x  = 7; glutamine: 242 s, s _x  = 3; hyperoxia: 231 s, s _x  = 3; hyperoxia + glutamine: 228 s, s _x  = 5; P < 0.01) were significantly improved in hyperoxic conditions. There was some evidence that glutamine ingestion increased Δ[Vdot]O_2max in normoxia, but not hyperoxia (interaction drink/FiO₂, P = 0.04), but there was no main effect or impact on performance. Overall, the data show no effect of glutamine ingestion either alone or in combination with hyperoxia, and thus no limiting effect of the tricarboxylic acid intermediate pool size, on oxidative metabolism and performance during maximal exercise.  相似文献   

Transfer of momentum from different arm segments to a light movable target during a straight punch thrown by expert boxers     

N C. Spurway  B Ekblom  T D. Noakes  P D. Wagner 《Journal of sports sciences》2013,31(6):517-531

Abstract

Three modern views about the factors limiting oxygen uptake in healthy humans are set against the original (early 1920s) concept of A. V. Hill and colleagues. The majority view for most of the intervening time has been that cardiac output is the essential limiting function. Among recent research in support of this contention is that, in quadrupeds, pericardiectomy, which allows greater diastolic filling, elevates maximum oxygen uptake; however, the relevance to bipedal exercise can be questioned. In any case, algebraic analyses of model systems indicate that all identifiable stages on the oxygen transport pathway, from pulmonary diffusion to oxidative phosphorylation in skeletal muscle mitochondria, materially influence maximum uptake. Thus, if a high cardiac output is to be of benefit, all the other steps must function better too. Nevertheless, these two viewpoints concur that the limit to maximum oxygen uptake is somatic. In contrast, there are strong indications that at altitudes where oxygen availability is about half that at sea level, cerebral oxygenation is a limiting factor, and some recent experiments raise the possibility that it might be a substantial influence at sea level also. Clearly, consensus cannot yet be reached on the question posed in the title.  相似文献   

The angiogenetic effect of intramuscular administration of b-FGF and a-FGF on cardiac muscle: The influence of exercise on muscle angiogenesis     

Anna Efthimiadou  Byron Asimakopoulos  Nikos Nikolettos  Alexandra Giatromanolaki  Efthimios Sivridis  Theodoros S. Lialiaris 《Journal of sports sciences》2013,31(8):849-854

Abstract

Although angiogenetic therapy using recombinant growth factors holds much hope for the treatment of ischaemic diseases, there are still many unanswered questions, including the method of administration, the correct dose of these factors, and the duration of the therapeutic approach. Exercise has also been suggested to induce neovascularizaiton in muscles. We evaluated the angiogenetic effects of the intramuscular administration of basic-fibroblast growth factor (b-FGF) and acidic-fibroblast growth factor (a-FGF) in rat heart, compared with rats who exercised daily. In conclusion, both the intramuscular administration of b-FGF and exercise increased significantly angiogenesis in the heart in contrast to the intramuscular administration of a-FGF, which was ineffective.  相似文献   

Effects of sensory-level high-volt pulsed electrical current ondelayed-onset muscle soreness     

Timothy W. Tourville  Declan A. J. Connolly  Brian V. Reed 《Journal of sports sciences》2013,31(9):941-949

Abstract

Ten healthy males and ten healthy females aged 21.5 ± 3.2 years (mean ± s) participated in the study, which was designed to evaluate the effectiveness of sensory level-high volt pulsed electrical current (HVPC) on delayed-onset muscle soreness (DOMS). Arm discomfort, elbow extension range of motion and isometric elbow flexion strength were obtained as baseline measurements. Delayed-onset muscle soreness was induced in the participants' dominant or non-dominant arm using two sets of 20 maximal eccentric elbow flexion contractions. After the induction of DOMS, the participants were randomly divided into an experimental condition (HVPC) or a placebo condition. The experimental condition consisted of 20 min of HVPC immediately after the induction of DOMS, and 20 min every 24 h for three consecutive days thereafter. The participants in the placebo condition received an intervention similar in design; however, no electrical current was administered. Baseline measurements were reevaluated at 24, 48, 72 and 96 h after the induction of DOMS. Three weeks later, the participants returned and the protocol was repeated on the contralateral limb, using the opposite intervention (HVPC or placebo). Repeated-measures analysis of variance revealed a significant increase in overall arm discomfort, decrease in elbow extension and decrease in isometric strength for both conditions over time. No significant main effect of treatment, or time-by-treatment interaction, was found for the HVPC condition when compared with the placebo condition for any variable. Sensory-level HVPC, as utilized in our application, was ineffective in reducing the measured variables associated with DOMS.  相似文献   

The effects of verbal encouragement and conscientiousness on maximal voluntary contraction of the triceps surae muscle in elite athletes     

Erdal Binboğa  Serdar Tok  Fatih Catikkas  Senol Guven  Senol Dane 《Journal of sports sciences》2013,31(9):982-988

Abstract

We investigated the effect of verbal encouragement on maximal voluntary contraction (MVC) level of the triceps surae muscle group. Our secondary focus was to examine whether the effect of verbal encouragement on MVC level varies as a result of conscientiousness. While the participants performed plantar flexion, MVCs of the triceps surae muscle group were measured using rectified and smoothed surface electromyography (rsEMG) during the absence and presence of verbal encouragement. Participants completed questions from the Five Factor Personality Inventory concerning conscientiousness and were divided into high- and low-conscientiousness groups according to a median split. The sample included 30 female and 53 male elite athletes. In the entire cohort, there was no significant difference in MVCs with and without verbal encouragement. When the sample was partitioned by conscientiousness scores, verbal encouragement led to a significant increase in MVC in the low-conscientiousness group, whereas verbal encouragement led to a non-significant decrease in MVC in the high-conscientiousness group. Percentage change in MVC across experimental conditions was significantly different between the groups, with a 9.72% increase during verbal encouragement of the low-conscientiousness group, and a 2.47% decrease during verbal encouragement of the high-conscientiousness group.  相似文献   

The Effects of Exercise on Muscle Tension and Subsequent Muscle Relaxation Training     

Linda Farrah Balog 《Research quarterly for exercise and sport》2013,84(2):119-125

Abstract

This investigation examined the effects of physical exercise on muscle tension and subsequent muscle relaxation training. Twenty college students participated in the first phase of the study, which included a 10-minute EMG baseline, 30 minutes of pedalling on a bicycle ergometer, followed by EMG measurements on the frontalis muscle for up to 3 hours after the end of exercise. The same subjects from Phase I went on to Phase II, which included eight 32-minute EMG biofeedback training (BFT) sessions, utilizing the frontalis muscle. Ten subjects randomly assigned to the experimental group received BFT following an acute exercise bout, while the 10 subjects in the control group received no treatment. The greatest decrease in muscle tension in Phase I occurred 90 minutes after the end of the exercise. This finding was not significantly different from the baseline, indicating that there was no relaxation effect as a result of exercise. In Phase II, significant differences between pre and post-test measurements in both groups indicated that learning of relaxation did occur. However, no significant differences were found between the two groups, indicating that physical exercise did not enhance the learning of EMG BFT.  相似文献   

Creatine Kinase Activity Weakly Correlates to Volume Completed Following Upper Body Resistance Exercise     

Marco Machado  Jeffrey M. Willardson  Dailson P. Silva  Italo C. Frigulha  Alexander J. Koch  Sergio C. Souza 《Research quarterly for exercise and sport》2013,84(2):276-281

In the current study, we examined the relationship between serum creatine kinase (CK) activity following upper body resistance exercise with a 1- or 3-min rest between sets. Twenty men performed two sessions, each consisting of four sets with a 10-repetition maximum load. The results demonstrated significantly greater volume for the 3-min condition (M = 4,156 kg, SD = 867, for 3 min; vs. M = 3,503 kg, SD = 759, for 1 min; p < .001), with no significant differences in delta CK activity between conditions (p = .574). Nevertheless, there was a weak correlation between the delta CK activity and total volume of exercise completed (r = .55 with a 1-min rest, and r =.45 with a 3-min rest). Therefore, the volume following upper body resistance exercise correlates weakly with serum CK levels, irrespective of rest interval length between sets.  相似文献   

Enzyme activity and myoglobin concentration in rat myocardium and skeletal muscles after passive intermittent simulated altitude exposure     

Santi Esteva  Pere Panisello  Joan Ramon Torrella  Teresa Pagés 《Journal of sports sciences》2013,31(6):633-640

Abstract

We studied the effect of intermittent hypobaric hypoxia exposure on lactate dehydrogenase and citrate synthase activities, together with myoglobin content, of rat myocardium, tibialis anterior, and diaphragm muscles. The intermittent hypoxia exposure programme consisted of daily 4-h sessions in a hypobaric chamber (5000 m) over a period of 22 days. Samples were taken at the end of the programme, and 20 and 40 days later, and compared with those of control animals. In myocardium, lactate dehydrogenase activity was significantly depressed in animals 20 days post-exposure (314.6 ± 15.3 IU · g^?1) compared with control animals (400 ± 14.3 IU · g^?1), while citrate synthase activity and myoglobin concentration showed a significant stepwise increase from control animals (88.2 ± 3.6 IU · g^?1 and 4.38 ± 0.13 μm · mg^?1) to animals 20 days (104.7 ± 3.7 IU · g^?1 and 5.01 ± 0.17 μm · mg^?1) and 40 days post-exposure (108.8 ± 6.5 IU · g^?1 and 5.11 ± 0.22 μm · mg^?1). In contrast, no differences were found in diaphragm and tibialis anterior muscles. Our results show that intermittent hypobaric hypoxia exposure increased the oxidative character of myocardium even 20 days after the hypoxic stimulus has ceased, and that this effect lasts for more than 40 days for citrate synthase activity and myoglobin concentration. These findings support our previous results on skeletal and cardiac muscle capillarization after passive intermittent simulated altitude exposure, thus providing morphofunctional and biochemical evidence for increased cardiac aerobic efficiency.  相似文献