EMG signs of neuromuscular fatigue related to the ventilatory threshold during cycling exercise

We questioned whether electromyographic (EMG) signs of neuromuscular fatigue accompany the changes in respiratory variables measured at the ventilatory threshold (VTh) during exercise on a cycloergometer. This was based on the assumption that the activation of muscle afferents sensitive to accumulation of lactate and potassium is suspected to elicit both the EMG signs of fatigue and hyperventilation. In 39 subjects performing an incremental cycling, the EMG estimates of neuromuscular fatigue in vastus lateralis were a non-linear increase in root mean square (RMS), a decrease in median frequency (MF), a non-linear increase in low-frequency EMG energies (EL), and/or a decrease in high-frequency energies (EH). VTh was determined from a non-linear increase in VCO2 [VTh(VCO2 slope)] and an increased value of the respiratory equivalent for oxygen [VTh(VE/VO2)]. We measured a significant increase in venous blood concentration of lactate and potassium, and a significant pHv fall at VTh. One EMG estimate of fatigue was detected in 33/39 individuals and two EMG estimates in 17 subjects. Highly significant positive correlations were found between the oxygen uptakes corresponding to each EMG estimate and to each detection criterion of VTh. These observations suggest that the activation of muscle sensory pathways contribute to the mechanism of VTh.     

Acute physiological effects of exhaustive whole‐body vibration exercise in man

Vibration exercise (VE) is a new neuromuscular training method which is applied in athletes as well as in prevention and therapy of osteoporosis. The present study explored the physiological mechanisms of fatigue by VE in 37 young healthy subjects. Exercise and cardiovascular data were compared to progressive bicycle ergometry until exhaustion. VE was performed in two sessions, with a 26 Hz vibration on a ground plate, in combination with squatting plus additional load (40% of body weight). After VE, subjectively perceived exertion on Borg’s scale was 18, and thus as high as after bicycle ergometry. Heart rate after VE increased to 128 min^–1, blood pressure to 132/52 mmHg, and lactate to 3·5 m M . Oxygen uptake in VE was 48·8% of VO_2max in bicycle ergometry. After VE, voluntary force in knee extension was reduced by 9·2%, jump height by 9·1%, and the decrease of EMG median frequency during maximal voluntary contraction was attenuated. The reproducibility in the two VE sessions was quite good: for heart rate, oxygen uptake and reduction in jump height, correlation coefficients of values from session 1 and from session 2 were between 0·67 and 0·7. Thus, VE can be well controlled in terms of these parameters. Surprisingly, an itching erythema was found in about half of the individuals, and an increase in cutaneous blood flow. It follows that exhaustive whole‐body VE elicits a mild cardiovascular exertion, and that neural as well as muscular mechanisms of fatigue may play a role.     

Use of recombinant human erythropoietin in combination with parenteral iron in the treatment of postpartum anaemia

The authors compared the effect of recombinant human erythropoietin (rhEPO) in combination with iron with that of iron therapy only in the treatment of postpartum anaemia. Ninety patients (30 patients/group) received either rhEPO (300 U kg⁻¹, i.v. or s.c., once) and iron (parenteral and oral), or iron therapy only. Erythropoiesis was assessed by haemoglobin and haematocrit increase, absolute reticulocyte counting and reticulocyte flow cytometry. Ferrokinetics was assessed by serum ferritin, transferrin and transferrin saturation measurements. There was no difference before therapy for baseline haematological values or iron status. Patients with endogenous EPO levels below 145 mU mL⁻¹ had a significant benefit from intravenous rhEPO administration with highest haematocrit and haemoglobin levels 4 and 14 days after therapy. rhEPO-treated groups showed a higher absolute reticulocyte count 1 and 4 days after therapy and an elevated percentage of high fluorescent reticulocytes (HFRs). Parenteral iron therapy caused a significant increase of ferritin and transferrin saturation, while transferrin concentration decreased. Ferritin and transferrin levels were lowest after i.v. administration of rhEPO, 1 and 4 days after therapy. C-reactive protein concentration was highest in patients who underwent caesarean section until the end of the observation period. A single dose of rhEPO in combination with iron was more effective in treating postpartum anaemia than iron therapy only, in patients who had low EPO levels despite peripartal blood loss. Postpartum low endogenous EPO levels might be a consequence of inhibiting inflammatory cytokines that are released after spontaneous or operative deliveries.     

Effects of erythropoietin on muscle O2 transport during exercise in patients with chronic renal failure.

Erythropoietin (rHuEPO) has proven to be effective in the treatment of anemia of chronic renal failure (CRF). Despite improving the quality of life, peak oxygen uptake after rHuEPO therapy is not improved as much as the increase in hemoglobin concentration ([Hb)] would predict. We hypothesized that this discrepancy is due to failure of O2 transport rates to rise in a manner proportional to [Hb]. To test this, eight patients with CRF undergoing regular hemodialysis were studied pre- and post-rHuEPO ([Hb] = 7.5 +/- 1.0 vs. 12.5 +/- 1.0 g x dl-1) using a standard incremental cycle exercise protocol. A group of 12 healthy sedentary subjects of similar age and anthropometric characteristics served as controls. Arterial and femoral venous blood gas data were obtained and coupled with simultaneous measurements of femoral venous blood flow (Qleg) by thermodilution to obtain O2 delivery and oxygen uptake (VO2). Despite a 68% increase in [Hb], peak VO2 increased by only 33%. This could be explained largely by reduced peak leg blood flow, limiting the gain in O2 delivery to 37%. At peak VO2, after rHuEPO, O2 supply limitation of maximal VO2 was found to occur, permitting the calculation of a value for muscle O2 conductance from capillary to mitochondria (DO2). While DO2 was slightly improved after rHuEPO, it was only 67% of that of sedentary control subjects. This kept maximal oxygen extraction at only 70%. Two important conclusions can be reached from this study. First, the increase in [Hb] produced by rHuEPO is accompanied by a significant reduction in peak blood flow to exercising muscle, which limits the gain in oxygen transport. Second, even after restoration of [Hb], O2 conductance from the muscle capillary to the mitochondria remains considerably below normal.     

Influence of oxygen administration on pulmonary haemodynamics and tissue oxygenation during exercise in COPD patients with different ACE genotypes

We previously found that the angiotensin-converting enzyme (ACE) DD genotype is associated with exaggerated pulmonary hypertension and disturbance of tissue oxygenation during exercise in chronic obstructive pulmonary disease (COPD) patients. This study was designed to compare the effect of oxygen administration on pulmonary haemodynamics and tissue oxygenation during exercise in COPD patients with different ACE genotypes. Forty-three COPD patients (II=16, ID=12, DD=15) underwent right heart catheterization, and then performed an exercise test with room air or oxygen. We measured pulmonary haemodynamic variables and indices of tissue oxygenation such as mixed venous oxygen tension (PVO2) and arterial lactate concentration, both at rest and after exercise. The magnitude of difference in mean pulmonary arterial pressure and pulmonary vascular resistance after exercise between breathing of room air and breathing of oxygen did not significantly differ among the three groups. PVO2 after exercise with room air or oxygen was significantly higher in patients with the II genotype than in those with the ID or DD genotype. In contrast, lactate concentration after exercise with room air or oxygen was significantly lower in patients with the II genotype than in those with the ID or DD genotype. Moreover, the magnitude of difference in PVO2 and lactate concentration after exercise between breathing of room air and breathing of oxygen was the II>ID>DD genotype. These findings suggest that the ability of oxygen administration to improve tissue oxygenation during exercise is associated with the ACE genotypes in COPD patients.     

肾移植受者康复期运动护理干预的效果研究

目的 探讨康复运动护理干预对出院肾移植受者的作用.方法 选取某三级甲等医院64例出院肾移植受者为研究对象,将其随机分为实验组和对照组各32例.对实验组肾移植受者实施3个月的康复运动护理干预,对照组进行出院后常规康复护理,评估比较2组的BMI(body mass index,体重指数)、血压及心率.结果 干预前2组的BMI、血压等生理指标比较无显著差异,具有可比性.干预后实验组的BMI、血压低于对照组,差异显著;而心率差异不明显.结论 康复运动护理干预有助于提高受者的生活质量,促进整体康复.     

悬吊运动技术对运动引起的腰痛的疗效分析

目的：观察悬吊运动技术（SET）对运动引起的腰痛的疗效，并与传统推拿治疗比较，为推广新的物理疗法提供依据。方法：将29例因运动引起腰痛的受试者随机分为两组，SET组15例，推拿组14例，分别进行SET治疗和推拿治疗，疗程共8周，实验开始和结束时进行VAS评分和血清CK、LDH测试。结果：①VAS评分在治疗后分别为SET治疗组1.76±1.58，推拿治疗组3.08±2.35，与治疗前相比均明显下降(P<0.01),且SET组低于推拿组(P<0.01)；②血清测试中，CK治疗后分别为SET治疗组41.32±6.88，推拿组48.75±7.12，LDH治疗后分别为SET组866±100.02，推拿组955±102.6，CK与LDH治疗后均明显下降(P<0.01)，LDH变化SET组更加明显(P<0.05)，但CK变化与推拿组相比不明显。结论：悬吊运动技术对运动性腰痛有着较好的治疗效果，由于SET技术具有明显缓解疼痛症状和治疗作用和降低血清LDH指标的效果，作为较新的无创理疗技术值得推广使用。     

Effect of human recombinant erythropoietin on anaemia and dialysis efficiency in patients undergoing continuous ambulatory peritoneal dialysis

The effect of long-term treatment with human recombinant erythropoietin (rHuEPO) has been studied in nine end-stage renal disease patients on continuous ambulatory peritoneal dialysis (CAPD). RHuEPO was administered subcutaneously twice weekly in rising doses starting with 50 Ukg-1 body weight. After 3 months of rHuEPO haemoglobin increased from 77.7 +/- 3.2 to 112.7 +/- 5.6 g l-1 (P less than 0.03), haematocrit rose from 22.8 +/- 1.2 to 30.3 +/- 1.7% (P less than 0.01). A consistent decrease in ferritin concentration was observed during this time (P less than 0.05). After 12 months of rHuEPO treatment and increased oral iron supplementation the rises of haemoglobin and haematocrit remained stable without other significant haematological changes. The rHuEPO-induced rise in haematocrit was associated with an increased peritoneal ultrafiltration (UF) without change in diuresis and body weight. UF improved from 128 +/- 28 ml 4 h-1 dwell time to 273 +/- 45 ml 4 h-1 (P less than 0.03) within 3 months of rHuEPO treatment, and remained stable during the following study period (month 12: 253 +/- 43 ml 4 h-1, P less than 0.05). The rise in UF resulted in improved peritoneal clearances of creatinine, urea, potassium, and phosphate (P less than 0.05, month 3). No change was observed in serum urea, creatinine, calcium, and potassium. Serum phosphate increased throughout the first 6 months of rHuEPO (P less than 0.05). No severe adverse effects of rHuEPO treatment could be observed. The present results demonstrate that long-term subcutaneous administration of rHuEPO is effective in correcting renal anaemia in CAPD patients and may improve dialysis efficiency by increased peritoneal ultrafiltration.     

促红细胞生成素对大鼠体外循环后肾脏保护作用的研究

目的研究促红细胞生成素(EPO)对于大鼠体外循环(CPB)术后肾脏损伤的保护作用并探讨其相关机制。方法将30只雄性SD大鼠随机均分为Sham组、CPB组及EPO组,每组10只。Sham组建立CPB模型管道,不进行CPB;其他2组建立CPB,以最大流量≥100 mL/(kg.min)转流维持1 h,其中EPO组于转流前在预充液中加入EPO 3 000 U/kg。分别于肝素化后转流前(T0)、转流结束后(T1)和转流结束后0.5(T2)、1(T3)、2(T4)、24 h(T5)检测血清肌酐(SCr)、尿素氮(BUN)水平;T5时取肾脏组织,检测组织肿瘤坏死因子(TNF-α)、白细胞介素-1β(IL-1β)、白细胞介素-6(IL-6)等炎症因子水平;同时测定肾脏组织丙二醛(MDA)、过氧化氢酶(CAT)、超氧化物歧化酶(SOD)等氧化应激指标水平,并行HE染色观察组织形态学改变。结果 T0时3组SCr、BUN水平无显著差异;与CPB组相比,EPO组T1至T 5各时间点SCr、BUN水平明显下降(P<0.05),肾组织中TNF-a、IL-1β、IL-6等炎症因子水平均明显低于CPB组(P<0.05);CPB组MDA高于Sham组,CAT、SOD活性则较Sham组低;EPO组CAT、SOD活性高于Sham组;组织病理学检查显示,EPO组的肾小管上皮细胞肿胀、胞浆内空泡形成、间质出血等病理变化较CPB组明显减轻(P<0.05)。结论 EPO可能通过抑制炎症因子的表达,降低氧化应激损伤,达到减轻CPB后肾脏损伤的目的。     

负荷运动对能量代谢的影响及研究

目的探讨渐增负荷最大运动后的过量氧耗与血乳酸、血糖及氨基酸代谢的变化关系。方法受试者为10名男子健康大学生。采用活动跑台方法进行渐增负荷跑至力竭为止。结果运动结束30min,吸氧量恢复到安静水平时,血乳酸浓度仍比安静时水平高,运动中丙氨酸上升,运动结束30min丙氨酸减少,但并未恢复到安静时的水平。结论过量氧耗除用于血乳酸的消耗外,可能生要用于丙氨酸代谢中的糖新生。     

牛磺酸和/或训练对大鼠运动能力的影响

目的探讨牛磺酸和/或训练对大鼠运动能力的影响.方法50只雄性Wistar大鼠按体重随机分为安静对照组、力竭运动组、训练运动组、服牛磺酸运动组、服牛磺酸结合训练运动组.后4组进行跑台运动至力竭后,即刻取血测定血糖和血乳酸以及血清丙二醛(MDA)、乳酸脱氢酶(LDH)、谷草转氨酶(GOT)和肌酸激酶(CK).结果力竭运动后血糖显著降低,后5项血生化指标都显著升高(P均＜0.05),而补充牛磺酸和进行运动训练后这种变化幅度缩小和力竭运动时间延长.结论训练和补充牛磺酸都能提高大鼠运动能力,两者结合的效果更好.     

芪丹通脉片对运动训练大鼠力竭时间的影响

目的:通过观察芪丹通脉片对参与运动训练大鼠力竭时间的影响，探讨活血化淤类药物对机体力竭时间的影响及其作用机制。方法:10周龄雄性SD大鼠16只随机分为2组：单纯运动训练组及芪丹通脉片+运动训练组。芪丹通脉片+运动训练组灌服芪丹通脉片生理盐水溶液（3.24mg/kg），而单纯运动训练组给予灌服相同体积的生理盐水。实验期间两组大鼠先进行2 周适应性游泳训练，然后进行4 周递增负荷游泳训练并于第4 周末进行力竭运动实验并计算力竭时间。结果:芪丹通脉片+运动训练组的力竭时间显著高于单纯运动训练组。结论:6周灌注芪丹通脉片后可以改善大鼠疲劳训练的机能状态，延长力竭运动中的力竭时间。     

Effect of exercise intensity on oxygen consumption kinetics in non-exercising muscle during exercise

This study examined the effect of exercise intensity on the kinetics of muscle oxygen consumption in non-exercising forearm flexor muscles (VO(2mf)) during exercise. Seven healthy male subjects performed cycling exercise for 60 min at 30% of maximal oxygen consumption (%VO(2max)) and 30 min at 50% VO(2max) on separate days. The VO(2mf) values at rest and during exercise were measured by near-infrared spectroscopy. The VO(2mf) at 30% VO(2max) significantly increased to 1·2 ± 0·1-fold over resting value at 20 min after the beginning of exercise (P<0·05) and remained constant within 1·2- to 1·3-fold over resting value until 60 min during exercise. The VO(2mf) at 50% VO(2max) significantly increased to 1·2 ± 0·1-fold over resting value at 15 min after the beginning of exercise (P<0·05). Subsequently, the VO(2mf) at 50% VO(2max) increased with time to 1·3 ± 0·1-fold over resting value at 20 min after the beginning of exercise and to 1·5 ± 0·2-fold over resting value at 30 min. The VO(2mf) 15-30 min of exercise at 50% VO(2max) was significantly higher than that at 30% VO(2max) (P<0·05). These data suggest that the increase in VO(2mf) has a time lag from the beginning of exercise, and the kinetics of VO(2mf) during exercise differs with exercise intensity. Therefore, we conclude that the kinetics of VO(2mf) during exercise is dependent on exercise intensity.     

Characterization of the anaemia of chronic renal failure and the mode of its correction by a preparation of human erythropoietin (r-HuEPO). An investigation of the pharmacokinetics of intravenous erythropoietin and its effects on erythrokinetics

Studies were directed to characterization of the anaemia of renal failure of 11 patients on haemodialysis and determination of the way in which it is corrected by human erythropoietin derived from recombinant DNA expressed in Chinese hamster ovary cells (r-HuEPO) administered intravenously. Erythrokinetics before treatment showed that total red cell mass was below normal and that both erythron transferrin uptake and red cell survival were modestly reduced; treatment increased both total red cell mass and erythron transferrin uptake but did not change red cell survival in previously untransfused patients. When BFU-e and CFU-e from patient bone marrow were cultured in autologous serum we found no evidence for inhibitors of erythroid progenitor maturation in patient serum compared with normal. Erythroid expansion in response to r-HuEPO was not limited by the availability of iron, iron requirements for new red cell formation being met from stores (if adequate) or from oral iron supplements. In pharmacokinetic studies the plasma clearance of r-HuEPO could be expressed by a three-parameter exponential curve with T1/2 range of 2.3 to 7.3 h. T1/2 after the first dose of r-HuEPO was not significantly different from that after 14 to 54 weeks treatment when the erythron had expanded to a new steady state. Erythron transferrin uptake before treatment was related to endogenous production of erythropoietin estimated from the plasma clearance of the first dose of r-HuEPO administered intravenously. This finding suggested that the availability of erythropoietin was the main factor limiting expansion of the erythron. This conclusion was supported by the continuity of the relationship during the response to treatment.     

Red blood cell cation transports in uraemic anaemia: evidence for an increased K/CI co-transport activity. Effects of dialysis and erythropoietin treatment*

Abstract. This study examines the role of uraemia and the effect of different dialysis treatments on red cell cation transport. We evaluated the main cation transport systems in erythrocytes of non-dialysed end-stage renal disease (ESRD) subjects, of patients undergoing haemodialysis (HD) and continuous ambulatory peritoneal dialysis (CAPD), as well as the changes induced by human recombinant erythropoietin (r-HuEPO) administration. In uraemic undialysed and dialysed patients, we observed an increase in K/Cl co-transport activity and in shrinkage-induced amiloride-sensitive (HMA-sensitive) Na efflux (Na/H exchange) and a decrease in Na/K pump and Na/K/Cl co-transport activity, while Na/Li exchange was increased only in dialysed patients. In uraemic erythrocytes, we showed for the first time an increased K/Cl co-transport activity, which was cell age independent. Generally, the different method of dialysis (CAPD or HD) did not modify the cation transport abnormalities observed. During the treatment with r-HuEPO, all the systems, with the exception of the Na/K pump and Na/K/Cl co-transport, increased their activities following the increase of circulating young red cells. The changes produced under r-HuEPO administration were transient and cation transports returned to the baseline values within 100 days of treatment, indicating a primary and prominent pathogenetic role of uraemia in modulating the red cell membrane cation transport activities.     

大脑行为对等长收缩运动时心血管反应的调控作用与机制

目的：研究大脑行为修正对等长收缩运动（ＩＥ）心血管反应的调控及机制。方法：用气功入静作为大脑行为修正的模式,记录常态及入静态站桩（ＩＥ）时的心血管反应;用ＲＩＡ法测定血浆内源性啡肽类物质－亮氨酸脑啡肽、β－内啡肽、强啡肽的含量。结果：入静ＩＥ较常态ＩＥ心率、血压显著降低（Ｐ〈０．０１）,而血浆内源性啡肽类物质含量显著升高。结论：大脑行为可调节等长收缩时的心血管反应,与血浆血浆内源性啡肽类物质的调控     

极量、亚极量负荷运动状态下血乳酸代谢和血清酶活性变化的特征

目的探讨机体在不同功能状态下血乳酸(LD)代谢和血清酶活性的变化特征。方法应用跑台提供运动负荷,分别对48名受试者进行了安静状态时、亚极量和极量负荷运动后血清LD含量和乳酸脱氢酶(LDH)、酸性磷酸酶(ACP)、碱性磷酸酶(ALP)、肌酸激酶(CK)活性的测定。结果发现上述各项指标在机体处于不同功能状态时均发生了显著性变化(P<0.05或0.001)。结论极量、亚极量负荷运动时对机体的血乳酸代谢和有关血清酶活动性产生明显影响。     

Interindividual variability of surface EMG changes during cycling exercise in healthy humans

We studied surface electromyogram (SEMG) changes during 1‐h endurance cycling in 12 healthy subjects of whom five were involved in mountain bike training programme. The work load was set at 50% of the predicted maximal heart rate. The surface EMG and the compound evoked muscle action potential (M‐wave) from the vastus lateralis muscle were recorded at rest, during the 1‐h cycling period, and the 20‐min recovery period. The root mean square (RMS) and the median frequency (MF) of SEMG power spectrum were computed. In all subjects, there was no shift in the median frequency throughout the cycling period and the increase in RMS remained stable. In subjects untrained to endurance cyclism, the M‐wave duration increased at the end of the cycling period and these changes persisted for a consecutive 15‐min period during recovery of exercise. By contrast, in trained mountain bikers the M‐wave duration decreased after 2 min of exercise – the effect persisting for 2 min during recovery. These data suggest that the interpretation of M‐wave changes during cycling must take into consideration the sport practices of the subjects and also that SEMG power spectrum and M‐wave explore different electrophysiological events.