高温环境下急性力竭运动对大鼠心肌HSP70及血浆心钠素的影响

目的:探讨高温环境下急性力竭运动对大鼠心肌组织HSP70及血浆心钠素(ANP)的影响。方法:雄性SD大鼠48只,随机分为安静对照组(C)、运动后即刻组(E)、高温暴露1小时组(H)、高温运动后即刻组(HE)、运动后24小时恢复组(E’)和高温运动后24小时恢复组(HE’)6组,每组8只。E、HE、E’、HE’组均进行一次性力竭跑台运动。H组在周围环境温度33℃、相对湿度50%的环境中高温暴露1小时。C、E、HE、H组在力竭运动后即刻宰杀,HE’、E’组分别在高温及常温下运动后均在温度23℃、相对湿度50%的常温环境下恢复24小时后宰杀。测试大鼠心肌组织HSP70及血浆ANP、血清CK-MB水平。结果:(1)E组和E’组HSP70表达量较C组显著升高(P<0.05,P<0.01),HE’组显著高于H组及E’组(P<0.01)。H组显著高于C组(P<0.01)。(2)E组ANP和CK-MB水平显著高于C组(P<0.01),HE组显著高于H组(P<0.05);E’组和HE’组分别显著低于E组和HE组(P<0.01)。结论:(1)高温和运动均会诱导心肌HSP70高表达且24小时后表达最高,高温环境增强了力竭运动引起的HSP70的高表达,这可能会对高温及运动后造成的心肌损伤有一定的修复作用。(2)力竭运动即刻血浆心钠素升高,改善了心肌血液供应,同时也提示心肌有潜在受损的可能,但高温环境并未加强力竭运动所致的心钠素水平的增加。     

高温高湿环境下递增负荷大强度运动对人体血清白细胞介素12的影响

目的:探讨高温高湿环境下大强度运动对人体血清白细胞介素12(interleukin-12,IL-12)的影响。方法:20名受试者随机分为运动组和暴露组,运动组在温度33℃、相对湿度分别为40%±2%(RH40%)和80%±2%(RH80%)的环境下进行递增负荷力竭跑台运动,两次不同湿度运动间隔1周。跑速从8 km/h开始,每分钟增加0.8 km/h,增加到16 km/h时不再增加,然后逐级递增坡度,以0.5%为起始坡度,实验过程中以受试者不能维持相应跑速,并自述不能坚持时终止运动。暴露组在高温中静坐,两者同时进出高温环境房。实验前和实验后即刻抽取静脉血。采用ELISA方法检测血清IL-12、皮质醇。结果:运动组RH40%和RH80%环境下运动后IL-12均显著性降低(P<0.05);暴露组IL-12在RH40%暴露后出现降低趋势,RH80%暴露后显著性下降(P<0.05)。运动组RH40%和RH80%环境下运动后血清皮质醇均显著升高(P<0.01,P<0.05);暴露组血清皮质醇RH40%暴露前后无显著性差异,RH80%暴露后显著性降低(P<0.01)。结论:高温环境下,无论相对湿度高低,进行递增负荷大强度运动后血清IL-12均降低,可能由血清皮质醇显著升高对IL-12产生抑制作用所引起,但高温环境下运动引起免疫抑制的机制有待研究。     

不同湿度高温环境下机体有氧运动能力相关指标比较

目的:探讨不同湿度高温环境对有氧运动能力的影响。方法:随机选取10名男性大学生为对象,设定环境温度为33℃,相对湿度分别为20%、40%、60%、80%作为模型,实验时间4周,两次测试之间间隔1周。测试时受试者进行递增负荷跑台运动,以8 km/h为起始速度,每分钟增加0.8 km/h到16 km/h为止,然后逐级加坡度,0.5%为起始坡度,每分钟递增0.5%直至受试者不能坚持,运动过程中监测心率、摄氧量、每分钟通气量(VE)以及主观用力感觉指数(RPE),测试前及结束后无名指采血测试血乳酸。结果:不同湿度高温环境下运动VE、最大心率(HRmax)、最大摄氧量(VO2max)无显著性差异,60%相对湿度下运动时VO2max(3831.7±313.16 ml/min)、VE(137.5±9.38 L/min)、HRmax(199.1±8.29 beat/min)均较其余相对湿度大。20%相对湿度组运动后3 min及5 min血乳酸较80%湿度组显著升高(P<0.05),60%相对湿度组运动后3 min血乳酸亦显著高于80%湿度组(P<0.05)。80%相对湿度组运动后1 min RPE仍显著高于40%相对湿度组(P<0.05),20%相对湿度组RPE值增加较缓慢,运动至第7和10 min时RPE值显著低于60%相对湿度组(P<0.05)。结论:与其余湿度相比,33℃高温环境下,80%相对湿度中机体有氧运动能力并未得到充分发挥。     

高温环境下急性力竭运动对大鼠下丘脑单胺类神经递质的影响

目的:探讨高温条件下急性力竭运动对大鼠下丘脑单胺类神经递质的影响。方法:16只雄性SD大鼠经适应性跑台训练后随机分为常温运动组(E)和高温运动组(HE),每组8只。E组和HE组大鼠分别在常温环境(23℃,约50%相对湿度)和高温环境(33℃,约50%相对湿度)中进行一次性力竭跑台运动。两组大鼠均在急性力竭运动后即刻宰杀。记录大鼠实验前后肛温(Tr)变化及力竭运动时间,运用高效液相色谱法测试大鼠下丘脑单胺类神经递质。结果:HE组大鼠急性力竭运动时间显著小于E组(P<0.01),而Tr显著高于E组(P<0.01);HE组大鼠下丘脑去甲肾上腺素(NE)浓度显著高于E组(P<0.01);两组大鼠5羟色胺(5-HT)、多巴胺(DA)、5羟色胺与多巴胺比值(5HT/DA)之间无显著性差异(P>0.05),但HE组大鼠5-HT和DA代谢产物5羟色氨酸(5-HIAA)与3,4-二羟基苯乙酸(DOPAC)均显著低于E组(P<0.05)。结论:(1)高温环境明显降低大鼠运动能力,大鼠核心温度升高是影响高温环境中运动能力的关键性因素,而非下丘脑单胺类神经递质的变化。(2)高温环境在一定程度上减弱了力竭运动对大鼠下丘脑单胺类神经递质的影响。     

热习服对中长跑运动员湿热环境下运动体液调节激素及Hsp70的影响

目的:探讨热习服对湿热环境下运动机体体液调节激素ALD、AVP、ANP、NE及Hsp70的影响。方法:16名中长跑运动员随机分为热习服组(HA)和对照组(HC),每组各8人;HA组先进行10天的热习服方案,使机体产生热习服,然后进行一次33℃、80%RH湿热环境下的40min、70%VO2max运动强度的热负荷运动;HC组不经过热习服阶段,直接进行一次同于热习服组的热负荷运动。热负荷运动前后测试实验对象的热应激的生理学指标及体液调节激素ALD、AVP、ANP、NE及Hsp70的水平,观察两组实验对象测试指标在热负荷运动前后的变化。结果:热负荷运动后,HA组和HC组核心温度和心率均非常显著性升高(P<0.01),出汗率无显著变化;HA组热负荷运动后的核心温度和心率水平比对照组低、出汗率水平比对照组高,但两组间差异无统计学意义。与运动前相比,HA组和HC组热负荷运动后红细胞压积非常显著性升高(P<0.01)。与运动前相比,HA组和HC组运动后ALD和NE非常显著性升高(P<0.01),AVP显著性升高(P<0.05),ANP显著性降低(P<0.05),Hsp70非常显著性升高(P<0.01),但组间检验均未见显著性差异(P>0.05)。结论:体液调节激素对维护热负荷运动过程中的机体水盐代谢和平衡发挥着重要作用;热习服一定程度上降低了机体对热负荷运动应激的生理生化热调节反应,提高了机体适应运动热环境的能力。     

热习服对高温力竭运动大鼠体液调节激素及下丘脑抗利尿激素合成的影响

目的:研究热习服对高温力竭运动大鼠血清Na+、K+、抗利尿激素(ADH)、醛固酮(ALD)、心钠素(ADH)含量和下丘脑AVP合成的影响。方法:24只雄性Wistar大鼠随机分为空白对照组(A组)、高温力竭组(B组)、热习服后高温力竭组(C组)。常温环境温度25℃,湿度50%;高温环境温度38℃,湿度50%。A组不进行任何处理,C组每天在高温环境下以18 m/min、坡度0在跑台训练14天,第15天B组和C组在高温环境下以20 m/min、坡度0运动到力竭。实验前后各组大鼠称量体重并测肛温,记录B、C组大鼠力竭运动时间。后麻醉取血和下丘脑,测定血清Na+、K+、ANP、ADH、ALD含量,RT-PCR测定下丘脑ADH mRNA表达。结果:(1)C组大鼠力竭运动时间(75.20±15.39 min)明显长于B组大鼠(27.67±4.80 min,P<0.01)。(2)C组大鼠体重丢失%明显高于B组(P<0.01);C组大鼠血浆渗透压(316.50±3.63 mmol/L)明显高于B组(304.75±5.90 mmol/L,P<0.01)。(3)B、C组大鼠血清ADH浓度显著高于A组(P<0.05),同时C组显著低于B组(P<0.05);B组和C组大鼠血清ALD浓度高于A组(P<0.01);B组和C组大鼠血清ANP浓度低于A组(P<0.05)。(4)B组大鼠下丘脑ADH mRNA表达(1.51±0.18)比A组(1.04±0.18)升高(P<0.01),C组表达(1.23±0.38)也高于A组(P<0.05)。结论:热习服明显提高大鼠在高温环境下的运动能力。热习服后,血液抗利尿激素浓度降低,下丘脑渗透压感受器"调定点"上移,血浆渗透压变化与下丘脑分泌ADH不一致。     

自体骨髓单个核细胞移植治疗后重度缺血性心力衰竭患者血浆Apelin水平变化及其临床意义

目的研究骨髓单个核细胞(BMMC)移植治疗前后缺血性心力衰竭(IHF)患者血浆Apelin水平及心功能的变化。方法纳入40例IHF患者,分为自体骨髓单个核细胞(BMMC)移植组(n=20)及常规治疗组(n=20),分别行BMMC移植及内科常规治疗,另选择20例心功能正常者作为健康对照组。检测各组血浆Apelin、脑钠肽(BNP)基线水平及两组IHF患者经治疗后的血浆Apelin、BNP水平。两组IHF患者治疗前后行超声心动图检查。结果治疗前,与健康对照组比较,BMMC移植组和常规治疗组患者血浆Apelin基线水平均显著降低(P<0.01),血浆BNP基线水平均显著升高(P<0.01),而两组IHF患者间差异无统计学意义(P>0.05)。BMMC移植组移植后患者NYHA分级降低,24h尿量增多,常规治疗组无明显变化。BMMC移植组治疗后7d,患者血浆Apelin水平较基线水平明显升高(P<0.05),21d则显著升高(P<0.01);常规治疗组患者血浆Apelin水平治疗前,治疗后72、1d差异无统计学意义(P>0.05)。7d时BMMC移植组患者血浆Apelin水平高于常规治疗组(P<0.05),21d这种差异则更加显著(P<0.01)。BMMC移植组治疗后7d,患者血BNP水平与移植前比较明显下降(P<0.05),21d时仍明显降低(P<0.05),而常规治疗组患者血浆BNP水平治疗前、治疗后7d和治疗后21d差异无统计学意义(P>0.05)。7d和21d时BMMC移植组患者血浆BNP水平均低于常规治疗组(P<0.05)。结论经BMMC移植治疗后重度IHF患者心功能明显改善,Apelin升高可能是这种改善的重要效应。     

不同强度运动后大鼠心肌细胞热休克蛋白72mRNA的表达

目的 :探讨不同运动强度和持续时间运动对大鼠心肌细胞热休克蛋白 72mRNA表达的影响。方法 :分别使SD大鼠进行低强度 (6 0 %VO2 max)、中等强度 (75 %VO2 max)和高强度 (85 %VO2 max)跑台运动 1天、2天和 3天 ,在末次运动结束后 2 4小时以RT -PCR法检测大鼠心肌细胞热休克蛋白 72mRNA的表达。结果 :在安静情况下大鼠心肌细胞存在HSP72mRNA的基础结构性表达 ;低强度运动 1天后心肌细胞HSP72mRNA表达与对照组相比无显著性差异 ,但随着运动时间的延长 ,HSP72mRNA表达逐渐增加 ;中等强度运动后心肌细胞HSP72mRNA表达随运动持续时间的延长显著增加 ,但运动 2天和 3天组表达量无显著性差异 ;大强度运动后心肌细胞HSP72mRNA表达随运动持续时间的延长显著增加。结论 :运动可以造成心肌细胞HSP72mRNA的表达增加 ,不同强度运动诱导心肌细胞HSP 72mRNA表达程度不同 ,且与运动持续时间存在内在关系。     

补液对湿热环境中青少年中长跑运动员运动时感觉反应的影响

目的:评估湿热环境中补液对青少年中长跑运动时感觉反应的影响,探讨感觉反应之间的相关关系。方法:采用随机对照交叉试验设计,8名男性青少年中长跑运动员均需完成高温高湿运动(对照)和高温高湿补液运动(补液)两阶段试验。试验时,对照阶段运动员禁止饮食,在33℃、相对湿度80%的环境房内先站立10min,随后以70%VO2max强度蹬骑功率自行车40min或至力竭运动终止。补液阶段运动员进入环境房前15min、运动开始后20min分别补充200ml某饮料,其他过程与对照阶段一致。两个阶段之间洗脱10天。测量被试进入环境房前后的直肠温度(Tre),运动10min和终止时的环境症状量表值(ESQ),运动10、30 min及终止时的主观疲劳感觉(RPE),运动0、10、30 min及终止时的口渴感觉(TST)、温度感觉(THM)和肌肉疼痛感觉(MPN)评分。结果:16人次试验中,12人次在达到设置时间前力竭,补液阶段的平均运动时间显著长于对照阶段(P<0.05);各观察时间点RPE、TST、THM和MPN评分随运动时间延长均显著升高(P<0.001);对照阶段运动30min时的RPE、TST评分显著高于补液阶段(P<0.05),两个阶段其他时间点的感觉反应评分均未见显著性差异(P>0.05)。运动终止时,两阶段Tre未见显著性差异(P>0.05)。对照阶段ESQ量表中条目1、3、6、11评分显著高于补液阶段(P<0.05)。RPE与TST、THM、MPN评分的相关系数分别为0.520(P<0.05)、0.777(P<0.01)及0.420(P<0.05)。结论:补液可增强湿热环境下青少年中长跑运动员运动时间。湿热环境下运动时RPE与TST、THM、MPN评分相关。     

高温高湿环境与常温环境运动中能量消耗的差异

目的:比较高温高湿环境和常温环境中不同运动强度下能量消耗的差异,为高温高湿环境中的训练和比赛提供参考。方法:10名成年男性分别在湿热环境(温度33±1℃,相对湿度65%±3%)和常温环境(温度23±2℃,相对湿度45%±2%)下,分别完成40%VO2max、60%VO2max、80%VO2max三个强度的跑台运动,运动时间20min。使用固定式气体代谢仪(Cortex Metalyzer 3B)测定运动过程中的能量消耗。结果:相比常温环境,机体在高温高湿环境同等强度运动中,呼吸频率显著增加,每分通气量非常显著性增高(P<0.01),但机体摄氧量,除60%VO2max强度外,增高不显著,呼吸交换率除60%VO2max强度外,显著性降低(P<0.05);机体脂肪的氧化量、供能量均显著性提高(P<0.05),供能比例除60%VO2max强度外,显著性增高(P<0.05);但机体的总能量消耗,除40%VO2max强度外,变化不显著。整个运动过程中,随运动强度的增加糖供能速率逐渐增加,但同等强度运动中,高温高湿环境中的糖供能速率较常温时低,脂肪供能速率较常温时高。结论:脂肪是高温高湿环境下安静和低强度运动中机体的主要供能物质。相比常温环境,高温高湿环境下同等强度运动中脂肪的供能比例更高。     

Exercise intensity and duration affect blood soluble HSP72

Soluble heat shock protein 72 (sHSP72) is suggested to play a role as a signalling molecule in the immune response to exercise. We were interested in whether duration and intensity of endurance running affect the level of inducible sHSP72 in the plasma/serum of endurance athletes. In the first part of the study, the influence of a continuous treadmill run of 60 min (CR) with an intensity of 75 % VO2max, a long treadmill run of 120 min (LR) with an intensity of 60 % VO2max, an extensive interval training program (IT; 10 x 1000 m, ca. 35 min, VO2max 88 %), and a competitive marathon run (MA) within 260 +/- 39 min (VO2max ca. 65 %) on the release of sHSP72 into the peripheral blood was tested. Blood samples were drawn before and directly after exercise, as well as 0.5, 1, 3, 24 h after exercise to determine sHSP72 levels. Secondly, we compared the effects of two exercise bouts with identical duration (23.7 +/- 7 min) but different intensities (Exhaustive exercise (ET) at 80 % VO2max vs. moderate exercise (MT) at 60 % VO2max) on sHSP72 concentration. The sHSP72 levels in plasma/serum were analyzed using an enzyme immunoassay specific for inducible HSP72 (Stressgen,Victoria, Canada). Early, significant increases of sHSP72 were detected immediately after all types of exercise with highest levels after MA. ET induced significantly higher levels of sHSP72 compared with MT. Long-lasting, competitive endurance exercise induced a more pronounced response of sHSP compared with more intensive but shorter exercise. Exercise intensity was also an important influencing factor. A duration- and intensity-dependent role for sHSP72 in the exercise-induced changes of the immune response may be assumed.     

Heat shock protein responses to eccentric weight or treadmill exercise in active young females

Previous studies have shown the increase of heat shock protein (HSP72) following exercise in animals. The purpose of this study was to examine the effect of type of exercise on HSP72 response in active young females. Nineteen female physical education students were randomly divided into two groups: an endurance training group (ETG) and a weight training group (WTG). The exercise protocol in the ETG included incremental running to exhaustion performed at 65–75% VO_2max on a treadmill with a 0% grade. The subjects in the WTG also performed 4 sets of eccentric contractions of elbow flexors: two sets of 25 reps at 50% 1RM and two sets of 15–20 reps at 60% 1RM. Blood sampling from antecubital vein was done at baseline level (rest), mid-exercise and 30 min post-exercise in the same conditions, after a 12–14 h overnight fast. The samples were sent to a laboratory and centrifuged, and the serum used to analyse variables. A sandwich **Elisa and enzymatic assay were used for determination of HSP72 values and creatine kinase (CK) respectively. The data were analysed with repeated measures, LSD post hoc and independent t-test at p<0.05. The results showed HSP72 level alterations in mid- and post-tests were only significant in the ERG in comparison with baseline values (p=0.007, p=0.03 respectively). In addition, HSP72 level alterations within the ETG and WTG were only significant mid-test. Also CK levels insignificantly increased and decreased in the ETG and WTG respectively. The CK alterations in mid- and post-tests were insignificant between groups. Thus these results suggest that eccentric weight exercise induces a further increase in HSP72 levels.     

Exercise-induced muscle damage, plasma cytokines, and markers of neutrophil activation

INTRODUCTION: Unaccustomed eccentric exercise often results in muscle damage and neutrophil activation. We examined changes in plasma cytokines stress hormones, creatine kinase activity and myoglobin concentration, neutrophil surface receptor expression, degranulation, and the capacity of neutrophils to generate reactive oxygen species in response to in vitro stimulation after downhill running. METHODS: Ten well-trained male runners ran downhill on a treadmill at a gradient of -10% for 45 min at 60% VO2max. Blood was sampled immediately before (PRE) and after (POST), 1 h (1 h POST), and 24 h (24 h POST) after exercise. RESULTS: At POST, there were significant increases (P < 0.01) in neutrophil count (32%), plasma interleukin (IL)-6 concentration (460%), myoglobin (Mb) concentration (1100%), and creatine kinase (CK) activity (40%). At 1 h POST, there were further increases above preexercise values for neutrophil count (85%), plasma Mb levels (1800%), and CK activity (56%), and plasma IL-6 concentration remained above preexercise values (410%) (P < 0.01). At 24 h POST, neutrophil counts and plasma IL-6 levels had returned to baseline, whereas plasma Mb concentration (100%) and CK activity (420%) were elevated above preexercise values (P < 0.01). There were no significant changes in neutrophil receptor expression, degranulation and respiratory burst activity, and plasma IL-8 and granulocyte-colony stimulating factor concentrations at any time after exercise. Neutrophil count correlated with plasma Mb concentration at POST (r = 0.64, P < 0.05), and with plasma CK activity at POST (r = 0.83, P < 0.01) and 1 h POST (r = 0.78, P < 0.01). CONCLUSION: Neutrophil activation remains unchanged after downhill running in well-trained runners, despite increases in plasma markers of muscle damage.     

Exercise training increases heat shock protein in skeletal muscles of old rats

PURPOSE: The effects of chronic exercise training on the expression of heat shock protein (HSP) in skeletal muscle of senescent animals are unknown. Therefore, the purpose of this study was to investigate the effects of chronic exercise training on skeletal muscle HSP expression in both young and old rats. METHODS: Young adult (3 months) and old (23 months) female Fisher 344 rats were assigned to either a sedentary control or an endurance exercise trained group (N = 6 per group). Exercised animals ran (60 min.d-1, 5 d.wk-1) on a treadmill at approximately 77% VO2peak for 10 wk. After completion of the training program, the soleus (SOL), plantaris (PL), and the red (RG) and white portions (WG) of the gastrocnemius muscles were excised, and citrate synthase (CS) activity and the relative levels of HSP72 were determined. RESULTS: Training resulted in increases (P < 0.05) in VO2peak in both young (67.6 +/- 3.1 vs 86.9 +/- 1.6 mL.kg-1.min-1) and old animals (54.5 +/- 1.8 vs 68.2 +/- 2.2 mL.kg-1.min-1). Training increased CS activity and the relative levels of HSP72 (P < 0.05) in all four skeletal muscles in both young and old animals. Specifically, compared with age-matched sedentary controls, exercise training resulted in increased (P < 0.05) levels of HSP72 in skeletal muscles of both young (SOL + 22%, PL +94%, RG + 44%, WG + 243%) and old animals (SOL +15%, PL +73%, RG +38%, WG +150%). CONCLUSIONS: These findings reveal that the exercise-induced accumulation of HSP72 in skeletal muscle differs between fast and slow muscles. Further, these data indicate that the exercise-induced accumulation of HSP72 in highly oxidative skeletal muscles (SOL and RG) is similar between young and old animals. In contrast, aging is associated with a blunted expression of HSP72 in fast skeletal muscles (PL and WG) in response to chronic exercise.     

湿热环境暴露对氰化钠毒性和组织氧化应激反应的影响

目的探讨湿热环境下氰化物毒性作用变化规律及其对组织氧化应激反应的影响。方法以小动物湿热环境试验箱模拟高温高湿环境,测定不同温、湿度[温度（Ta）（20±0.5）℃、相对湿度（50±5）%,温度36℃及38℃、相对湿度（RH）（60±3）%]条件下氰化钠经腹腔注射KM小鼠的LD50。另将30只SD大鼠随机分为常温对照、常温中毒、湿热对照、湿热中毒及药物预防组,各组受试动物分别按以下因素单一或联合处理：（1）湿热应激：模拟箱内[温度（38±0.5）℃,相对湿度（60±3）%]60 min;（2）氰中毒：动物腹腔注射氰化钠3.6 mg/kg;（3）药物预防：给予谷胱甘肽、维生素C灌胃5 d。各组受试动物于热应激后60 min和（或）中毒30 min后测定脑、肝组织匀浆超氧化物歧化酶（superoxide dismutase,SOD）活性和丙二醛（malondialdehyde,MDA）含量。结果与20℃,RH50%时KM小鼠氰化钠中毒LD50（4.77 mg/kg）相比,（36±0.5）℃或（38±0.5）℃,RH 60%湿热环境中毒动物的LD50分别下降至4.66 mg/kg（P〉0.05）及4.17 mg/kg（P〈0.05）。20℃RH 50%条件下NaCN中毒后肝、脑组织SOD活力下降（P〈0.01）,MDA含量增加（P〈0.01）,而38℃RH 60%环境下NaCN中毒所致氧化应激改变更明显（P〈0.01）。药物预防可缓解相同条件下上述指标的改变（P〈0.01）。结论暴露于湿热环境下,小鼠氰化纳中毒的LD50可随环境温度的升高而降低。湿热环境和（或）氰化钠中毒两因素均可导致氧化应激指标的明显改变,二者同时作用可能具有联合效应。服用抗氧化药物可提高组织抗氧化应激能力。     

Time course of neuromuscular alterations during a prolonged running exercise

PURPOSE: This study investigated the time course of contractile and neural alterations of knee extensor (KE) muscles during a long-duration running exercise. METHODS: Nine well-trained triathletes and endurance runners sustained 55% of their maximal aerobic velocity (MAV) on a motorized treadmill for a period of 5 h. Maximal voluntary contraction (MVC), maximal voluntary activation level (%VA), and electrically evoked contractions (single and tetanic stimulations) of KE muscles were evaluated before, after each hour of exercise during short (10 min) interruptions, and at the end of the 5-h period. Oxygen uptake was also measured at regular intervals during the exercise. RESULTS: Reductions of MVC and %VA were significant after the 4th hour of exercise and reached -28% (P < 0.001) and -16% (P < 0.01) respectively at the end of the exercise. The reduction in MVC was highly correlated with the decline of %VA (r = 0.98, P < 0.001). M-wave was also altered after the fourth hour of exercise (P < 0.05) in both vastus lateralis and rectus femoris muscles. Peak twitch was potentiated at the end of the exercise (+18%, P = 0.01); 20- and 80-Hz maximal tetanic forces were not altered by the exercise. Oxygen uptake increased linearly during the running period (+18% at 5 h, P < 0.001). CONCLUSION: These findings suggest that KE maximal voluntary force generating capability is depressed in the final stages of a 5-h running exercise. Central activation failure and alterations in muscle action potential transmission were important mechanisms contributing to the impairment of the neuromuscular function during prolonged running.     

液相芯片检测高湿环境对大鼠T淋巴细胞因子表达的影响

目的 液相芯片技术检测大鼠血清中细胞因子的表达,探讨高湿环境对大鼠细胞因子的影响.方法 32只SD大鼠随机分为两组,高湿组与正常组,每组16只大鼠.采用人工气候箱模拟高湿环境,条件设置为温度25 ℃、相对湿度90%~95%.高湿组大鼠每天置于箱中10 h,其余时间与正常组一样饲养于常温常湿的清洁环境（温度25 ℃,相对湿度45%~50%）,连续20 d.动物模型制作完成后,取大鼠腹主动脉血,分离血清,应用Luminex200检测9种细胞因子的表达.结果 与正常组比较,高湿组IL-1α、IL-1β、IL-2、IL-6、IL-10血清水平显著升高（P＜0.05或P＜0.01）,IFNγ明显下降（P＜0.01）,TNFα、EGF、VEGF血清水平变化不明显（P＞0.05）.结论 高湿可引起大鼠血清细胞因子的改变,Th1/Th2类细胞因子平衡被打破,使大鼠的免疫自稳状态发生变化.     

Sodium loading aids fluid balance and reduces physiological strain of trained men exercising in the heat

PURPOSE: This study was conducted to determine whether preexercise ingestion of a highly concentrated sodium beverage would increase plasma volume (PV) and reduce the physiological strain of moderately trained males running in the heat. METHODS: Eight endurance-trained (.VO2max: 58 mL.kg(-1).min(-1) (SD 5); 36 yr (SD 11)) runners completed this double-blind, crossover experiment. Runners ingested a high-sodium (High Na+: 164 mmol Na+.L(-1)) or low-sodium (Low Na+: 10 mmol Na+.L(-1)) beverage (10 mL.kg(-1)) before running to exhaustion at 70% .VO2max in warm conditions (32 degrees C, 50% RH, V(a) approximately equal to 1.5 m.s(-1)). Beverages (approximately 757 mL) were ingested in seven portions across 60 min beginning 105 min before exercise. Trials were separated by 1-3 wk. Heart rate and core and skin temperatures were measured throughout exercise. Urine and venous blood were sampled before and after drinking and exercise. RESULTS: High Na+ increased PV before exercise (4.5% (SD 3.7)), calculated from Hct and [Hb]), whereas Low Na+ did not (0.0% (SD 0.5); P = 0.04), and involved greater time to exercise termination in the six who stopped because of an ethical end point (core temperature 39.5 degrees C: 57.9 min (SD 6) vs 46.4 min (SD 4); P = 0.04) and those who were exhausted (96.1 min (SD 22) vs 75.3 min (SD 21); P = 0.03; High Na+ vs Low Na+, respectively). At equivalent times before exercise termination, High Na+ also resulted in lower core temperature (38.9 vs 39.3 degrees C; P = 0.00) and perceived exertion (P = 0.01) and a tendency for lower heart rate (164 vs 174 bpm; P = 0.08). CONCLUSIONS: Preexercise ingestion of a high-sodium beverage increased plasma volume before exercise and involved less thermoregulatory and perceived strain during exercise and increased exercise capacity in warm conditions.     

Trained men display increased basal heat shock protein content of skeletal muscle

PURPOSE: 1) To compare the baseline levels of heat shock and antioxidant protein content in the skeletal muscle of trained and untrained humans and 2) to characterize the exercise-induced stress response of aerobically trained human skeletal muscle to an acute exercise challenge. METHODS: Resting muscle biopsies were obtained from the vastus lateralis muscle of six untrained and six aerobically trained young males. To characterize the stress response of a trained population, the trained subjects also performed a 45-min nondamaging running exercise protocol at an intensity corresponding to 75% of V O2max. Muscle biopsies were obtained from the vastus lateralis muscle at 48 h and 7 d after exercise. RESULTS: Trained subjects displayed significantly higher (P<0.05) resting levels of heat shock protein 60 (HSP60, 25%), alphaB-crystallin (43%), and manganese superoxide (MnSOD, 45%) protein content compared with untrained subjects. Trained subjects also exhibited no significant change (P > 0.05) in resting levels of HSP70 (16%), HSC70 (13%), and total superoxide dismutase (SOD) activity (46%) compared with untrained subjects. Resting HSP27 levels were unaffected by exercise training (P > 0.05). In the trained subjects, exercise failed to induce significant increases (P>0.05)in muscle content of HSP70, HSC70, HSP60, HSP27, alphaB-crystallin, and MnSOD protein content or in the activity of SOD at any time point after exercise. CONCLUSION: This study demonstrates for the first time that trained men display a selective up-regulation of basal heat shock and antioxidant protein content and do not exhibit a stress response to customary running exercise. It is suggested that an increase in these protective systems functions to maintain homeostasis during the stress of exercise by protecting against disruptions to the cytoskeleton/contractile machinery, by maintaining redox balance, and by facilitating mitochondrial biogenesis.