耐力训练对大鼠骨骼肌超微结构的影响

目的:探讨大鼠骨骼肌对中等负荷耐力训练的适应性变化。方法:实验于2004-02/09在第四军医大学基础部完成。选择健康雄性8周龄Wistar大鼠40只,进行上坡跑中等负荷运动,坡度是+5°。以16m/min的速度持续奔跑45min。每周训练6d,休息1d,持续8周。自由活动组5只设为对照组,不施加干预,饲养笼内自由活动。训练组按训练时间分为1,2,3,4,6,8周6个时间水平。每组分别为4,4,6,6,7,8只。按不同的训练时间水平处死大鼠,取比目鱼肌肌腹,用30g/L戊二醛和体积分数0.1的甲醛固定,苏木精伊红染色,中性树胶封固,光镜观察。每组任选4只大鼠的比目鱼肌制备电子显微镜切片,电镜观察在不同训练阶段大鼠比目鱼肌超微结构的变化。主要观察肌原纤维和肌节排列的规则程度,肌节明带(I带)和暗带(A带)的完整情况与位置关系;Z线异常变化包括Z线流、Z线模糊、Z线扭曲和Z线消失,有上述任何一种情况出现的Z线均算作异常Z线。异常Z线数占被观察Z线总数的百分率即是Z线异常率。每只动物所观察的Z线总数在1500条以上行方差分析。各组间差别用独立样本t检验进行比较。结果:40只大鼠实验过程中无死亡,全部进入结果分析。①对照组肌纤维排列紧密,横切片上纤维大小较一致,呈多角形;在纵切片上可见到清晰、规则的肌横纹,肌核均匀分布在肌纤维周围的肌膜下,无增生、肿胀或固缩。组织间血管形态正常,无破裂;肌外膜无纤维增生。训练组可见程度不一的肌肉空泡变性、颗粒变性和透明样变性等,以3周组明显。可见炎症细胞浸润。②训练组比目鱼肌Z线异常率在训练后开始增加,在第3周达到高峰,后逐渐减少。训练组2,3,4周组比目鱼肌Z线异常率均高于对照组,差异显著(10.8±0.566,15.763±0.537,11.812±1.274,2.713±0.203,P<0.01)。结论:肌肉组织学病理改变提示大鼠比目鱼肌发生运动性肌肉损伤,并在第3周时损伤最重,出现骨骼肌结构相对“薄弱期”。运动4周后,Z线异常率逐渐降低,病理改变逐渐减少。说明肌肉损伤有一个逐渐加重后经修复逐渐减轻的过程。在损伤积累的同时,肌肉表现出良好的适应能力,但适应的机制尚不清楚。     

耐力训练对大鼠骨骼肌超微结构的影响

目的：探讨大鼠骨骼肌对中等负荷耐力训练的适应性变化。方法：实验于2004-02／09在第四军医大学基础部完成。选择健康雄性8周龄Wistar大鼠40只进行上坡跑中等负荷运动，坡度是＋5&;#176;。以16m／min的速度持续奔跑45min。每周训练6d，休息1d，持续8周。自由活动组5只设为对照组，不施加干预，饲养笼内自由活动。训练组按训练时间分为1，2，3，4，6，8周6个时间水平。每组分别为4，4，6，6，7，8只。按不同的训练时间水平处死大鼠，取比目鱼肌肌腹，用30g/L戊二醛和体积分数0．1的甲醛固定，苏木精伊红染色，中性树胶封固，光镜观察。每组任选4只大鼠的比目鱼肌制备电子显微镜切片，电镜观察在不同训练阶段大鼠比目龟肌超微结构的变化。主要观察肌原纤维和肌节排列的规则程度，肌节明带（I带）和暗带（A带）的完整情况与位置关系；Z线异常变化包括Z线流、Z线模糊、Z线扭曲和Z线消失，有上述任何一种情况出现的Z线均算作异常Z线。异常Z线数占被观察Z线总数的百分率即是Z线异常率。每只动物所观察的Z线总数在1500条以上行方差分析。各组间差别用独立样本t检验进行比较。结果：40只大鼠实验过程中无死亡，全部进入结果分析。①对照组肌纤维排列紧密，横切片上纤维大小较一致，呈多角形；在纵切片上可见到清晰、规则的肌横纹，肌核均匀分布在肌纤维周围的肌膜下，无增生、肿胀或固缩。组织间血管形态正常，无破裂；肌外膜无纤维增生。训练组可见程度不一的肌肉空泡变性、颗粒变性和透明样变性等，以3周组明显。可见炎症细胞浸润。②训练组比目鱼肌Z线异常率在训练后开始增加．在第3周达到高峰，后逐渐减少。训练组2，3，4周组比目鱼肌Z线异常率均高于对照组，差异显著（10．8&;#177;0．566，15．763&;#177;0．537，11．812&;#177;1．274，2．713&;#177;0．203．P〈0．01）。结论：肌肉组织学病理改变提示大鼠比目鱼肌发生运动性肌肉损伤，并在第3周时损伤最重，出现骨骼肌结构相对“薄弱期”。运动4周后，Z线异常率逐渐降低，病理改变逐渐减少。说明肌肉损伤有一个逐渐加重后经修复逐渐减轻的过程。在损伤积累的同时，肌肉表现出良好的适应能力，但适应的机制尚不清楚。     

耐力运动对大鼠骨骼肌葡萄糖运载体基因表达的调节作用

本实验的目的是观察耐力运动对大鼠骨骼肌葡萄糖运载体（ＧＬＵＴ４）基因表达的影响。将Ｓｐｒａｇｕｅ Ｄａｗｌｅｙ大发为对照组和耐力运动组。耐力运动组大鼠进行６－７周的游泳训练。运用斑点印迹杂交和Ｎｏｒｔｈｅｒｎ印迹杂交法测试骨骼肌细胞内ＧＬＴ４基因表达。结果表明耐力运动 大鼠骨骼肌细胞内ＧＬＵＴ４基因表达明显增加，斑点印迹杂交测试表明耐力运动组大鼠与对照组大鼠比较，骨骼肌细胞内ＧＬＵＴ４ｍＲＮＡ增加     

耐力运动对大鼠葡萄糖运载体基因表达及转位的影响

目的　研究耐力运动对大鼠骨骼肌细胞葡萄糖运载体 4(glucosetransporter 4,GLUT4)基因表达及转位机制的影响。方法　将SD大鼠随机分为两组 :对照组和耐力运动组。耐力运动组大鼠进行 6周游泳训练。用Western印迹法检测大鼠骨骼肌细胞内膜和外膜的GLUT4蛋白含量 ,用Northern杂交法和斑点印迹法检测大鼠骨骼肌细胞内GLUT4mRNA含量。实验前后检测大鼠血清胰岛素和血糖浓度。结果　运动组大鼠经过 6周游泳训练后 ,与对照组大鼠相比 ,骨骼肌细胞内膜GLUT4含量增加 16.0 %(P <0 .0 1) ,细胞外膜GLUT4含量增加 71.9% (P <0 .0 1) ,骨骼肌细胞内GLUT4mRNA含量增加2 5 .6% (P <0 .0 1)。结论　耐力运动可增加骨骼肌细胞内GLUT4基因表达水平 ,促进骨骼肌细胞内的GLUT4从内膜向细胞外膜转位 ,从而提高骨骼肌细胞对葡萄糖的摄取和利用。     

耐力训练后减量训练模型大鼠骨骼肌肌浆网Ca2+的转运功能

背景:运动训练对骨骼肌超微结构的影响是运动医学中定量化的细胞生物学研究热点.目的:观察大鼠耐力训练后减量训练模型骨骼肌肌浆网的钙离子转运功能的变化.设计、时间及地点:随机对照动物实验,动物训练于2006-04/07在西安体育学院进行,生化实验于2006-07在西安交通大学生物实验中心完成.材料:2月龄雄性健康SD大鼠39只,体质量(220±20)g.方法:5只SD大鼠用于预实验.其余大鼠随机分为正常对照组8只、耐力训练组8只、耐力减训组18只.耐力训练组和耐力减训组递增训练周期均为6周,6周后将耐力减训组根据减训周期随机分为耐力减训2周,4周,6周组.对训练大鼠采用小动物跑台进行递增耐力负荷训练,减训组采用逐渐减少运动强度训练.主要观察指标:使片j酶偶联法测定大鼠腓肠肌肌浆网Ca2 -ATPase的活性;采用荧光分光光度计测量肌浆网最大Ca2 摄取量和释放量.结果:①肌浆网SRCa2 -ATP ase活性:耐力训练组较正常对照组显著性增加(P<0.01);耐力减训2周组与耐力训练组比较基本不变(P>0.05):耐力减训4周,6周组较耐力训练组下降(P<0.01).②肌浆网SR最大Ca2 摄取和释放率:耐力训练组显著性增加(P<0.01);耐力减训2周组与耐力训练组比较差异无显著性意义(P>0.05);耐力减训4周,6周组下降显著(P<0.01).结论:耐力训练6周后,SD大鼠骨骼肌肌浆网Ca2 ATPase的活性增强,钙离子的摄取和释放率增加.减量训练2周骨骼肌肌浆网Ca2 ATPase的活性、钙离子摄取和释放率下降不明显.4周更长时间骨骼肌肌浆网Ca2 ATPase的活性及钙离子摄取和释放率下降明显.     

耐力训练模型大鼠骨骼肌代谢酶与自由基变化

背景:骨骼肌代谢酶与自由基的变化与不同的运动方式和运动强度有关.目的:观察递增大强度耐力训练下大鼠骨骼肌代谢酶活性和自由基代谢的变化.方法:健康雄性SD大鼠,随机分为安静组和运动组,后者建立8周的递增大强度耐力训练模型,训练结束后取骨骼肌样本测试肌酸激酶、乳酸脱氢酶、谷草转氨酶、谷丙转氨酶、丙二醛、总抗氧化酶、过氧化氢酶水平.结果与结论:8周训练后,运动组大鼠肌酸激酶、乳酸脱氢酶、谷草转氨酶、谷丙转氨酶酶活性及丙二醛水平均高于安静组(P < 0.01或0.05),而总抗氧化酶、过氧化氢酶、谷胱甘肽过氧化物酶活性低于安静组(P < 0.05).说明8周的递增大强度的耐力训练能使骨骼肌受到一定的损伤,并且提示抗氧化酶活性的下降和部分代谢酶活性以升高之间有一定的关系.     

耐力训练模型大鼠骨骼肌代谢酶与自由基变化

背景：骨骼肌代谢酶与自由基的变化与不同的运动方式和运动强度有关。目的：观察递增大强度耐力训练下大鼠骨骼肌代谢酶活性和自由基代谢的变化。方法：健康雄性SD大鼠,随机分为安静组和运动组,后者建立8周的递增大强度耐力训练模型,训练结束后取骨骼肌样本测试肌酸激酶、乳酸脱氢酶、谷草转氨酶、谷丙转氨酶、丙二醛、总抗氧化酶、过氧化氢酶水平。结果与结论：8周训练后,运动组大鼠肌酸激酶、乳酸脱氢酶、谷草转氨酶、谷丙转氨酶酶活性及丙二醛水平均高于安静组（P〈0.01或0.05）,而总抗氧化酶、过氧化氢酶、谷胱甘肽过氧化物酶活性低于安静组（P〈0.05）。说明8周的递增大强度的耐力训练能使骨骼肌受到一定的损伤,并且提示抗氧化酶活性的下降和部分代谢酶活性以升高之间有一定的关系。     

The influence of gender on skeletal muscle endurance capacity

Abstract

Skeletal muscle function and its role in providing joint stability has been the focus of considerable interest over the last few years. A proven relationship between spinal pain and sub-optimal muscle function, including endurance capacity, affirms the importance of functional stability re-training in the management of patients with neuromusculoskeletal dysfunction. Clinical protocols, based upon the use of the same target forces, repetitions, and contraction times for both genders are currently used as a basis for evaluating changes in spinal muscle endurance capacity. However these protocols do not account for the gender-related differences in endurance capacity that have been shown to exist in some of the literature, where women have recorded higher values for endurance capacity compared with men. This paper reviews the literature that has sought to evaluate the influence of gender on endurance capacity, discusses the physiological mechanisms that may account for observed differences, and considers the possible clinical implications for physiotherapists.     

不同强度的耐力运动对糖尿病大鼠骨骼肌 GLUT4 mRNA表达的影响

目的探讨不同强度的耐力运动对糖尿病大鼠骨骼肌GLUT4 mRNA表达的影响.方法雄性SD大鼠,其中36只大鼠经尾静脉注射链脲霉素,建立糖尿病模型.然后随机分为低强度运动组(EL)、高强度运动组(EH)、低强度运动加胰岛素治疗组(LI)、高强度运动加胰岛素治疗组(HI)、胰岛素治疗非运动组(DI)和非胰岛素治疗非运动组(DM).6只SD大鼠为非运动正常血糖组(CN).耐力训练采用活动平板,胰岛素采用皮下注射,共8周.运用RT-PCR法测定骨骼肌GLUT4 mRNA.结果DM组骨骼肌GLUT4 mRNA表达水平显著低于其它各组(P＜0.05).LI组骨骼肌GLUT4 mRNA表达水平明显增高接近CN组,并且显著高于DI组.DI组GLUT4 mRNA含量与EL、EH、HI各组相当,差异无显著性意义.结论运动可以促进GLUT4 mRNA的表达,而运动强度对GLUT4 mRNA表达量无显著影响;低强度运动加胰岛素所具有最佳的GLUT4 mRNA表达水平是其它单独干预措施所无法替代的.     

耐力运动对2型糖尿病大鼠骨骼肌葡萄糖运载体4基因表达的影响

目的：探讨耐力运动对糖尿病大鼠骨骼肌葡萄糖运载体4（glucose transporter 4，GLUT4）mRNA表达的影响。方法：32只雄性2型糖尿病OLETF大鼠和13只雄性对照LETO大鼠随机分为6组：A1组OLETF运动组、A2组OLETF运动＋胰岛素组、B1组OLETF非运动组、B2组OLETF非运动＋胰岛素组、C组LETO运动组、D组LETO非运动组。A1、A2、C组参照Ploug报道的大鼠游泳运动方法运动12周。A2、B2组经肝门静脉予胰岛素10U／Kg的注射，1min后处死取材。Real—time PCR方法测定GLUT4 mRNA。结果：GLUT4 mRNA表达在A1组比B1组升高3倍．A2组比A1组升高13倍，B2组比B1组升高20倍，差异均有显著性意义；A2组比B2组GLUT4 mRNA升高2倍，差异无显著性意义。结论：耐力运动可以促进GLUT4 mRNA的表达，耐力运动和胰岛素对糖尿病治疗具有协同作用，两者不能相互替代。     

耐力训练对糖尿病大鼠骨骼肌p38信号激酶的调节作用

目的:研究不同强度的耐力训练对糖尿病大鼠骨骼肌细胞丝裂素活化蛋白激酶p38活性的调节作用,为制订适宜的糖尿病运动疗法程序提供分子生物学依据。方法:雄性SD大鼠34只,尾静脉注射链脲霉素,建立糖尿病模型。然后随机分为低强度运动组(E1,n=6)、高强度运动组(E2,n=6)、低强度运动加胰岛素治疗组(EI1,n=6)、高强度运动加胰岛素治疗组(EI2,n=6)、非胰岛素治疗非运动组(C,n=5)和胰岛素治疗非运动组(CI,n=5)。耐力训练采用活动平板,胰岛素皮下注射,共8周。运用化学发光法测定p38活性。结果:训练8周前后,EI1组安静血糖下降46%(P<0.01),其余各组血糖无明显下降。单次运动前后E1组、EI1组、EI2组和CI组血糖均见明显下降,其中EI1组血糖降低尤为显著达83%(P<0.01)。骨骼肌p38活性在EI1组显著高于其余各组(P<0.05),E1组显著高于E2组、C组、CI组(P<0.05)。结论:低强度运动训练以及低强度运动训练加胰岛素治疗均能显著提高糖尿病大鼠骨骼肌细胞p38信号激酶,提示低强度运动训练加胰岛素治疗是内源性胰岛素缺乏性糖尿病的适宜治疗方案。     

Effect of low-level laser therapy (808 nm) on skeletal muscle after endurance exercise training in rats

BACKGROUND:

Low-level laser therapy (LLLT) has been demonstrated to be effective in optimizing skeletal muscle performance in animal experiments and in clinical trials. However, little is known about the effects of LLLT on muscle recovery after endurance training.

OBJECTIVE:

This study evaluates the effects of low-level laser therapy (LLLT) applied after an endurance training protocol on biochemical markers and morphology of skeletal muscle in rats.

METHOD:

Wistar rats were divided into control group (CG), trained group (TG), and trained and laser irradiated group (TLG). The endurance training was performed on a treadmill, 1 h/day, 5 days/wk, for 8 wk at 60% of the maximal speed reached during the maximal effort test (Tmax) and laser irradiation was applied after training.

RESULTS:

Both trained groups showed significant increase in speed compared to the CG. The TLG demonstrated a significantly reduced lactate level, increased tibialis anterior (TA) fiber cross-section area, and decreased TA fiber density. Myogenin expression was higher in soleus and TA muscles in both trained groups. In addition, LLLT produced myogenin downregulation in the TA muscle of trained animals.

CONCLUSION:

These results suggest that LLLT could be an effective therapeutic approach for stimulating recovery during an endurance exercise protocol.     

Adaptive responses of human skeletal muscle to vibration exposure

The aim of this study was to investigate the effects of whole-body vibrations (WBV) on the mechanical behaviour of human skeletal muscle. For this purpose, six female volleyball players at national level were recruited voluntarily. They were tested with maximal dynamic leg press exercise on a slide machine with extra loads of 70, 90, 110 and 130 kg. After the testing, one leg was randomly assigned to the control treatment (C) and the other to the experimental treatment (E) consisting of vibrations. The subjects were then retested at the end of the treatment using the leg press. Results showed remarkable and statistically significant enhancement of the experimental treatment in average velocity (AV), average force (AF) and average power (AP) (P<0·05–0·005). Consequently, the velocity–force and power–force relationship shifted to the right after the treatment. In conclusion, it was affirmed that the enhancement could be caused by neural factors, as athletes were well accustomed to the leg press exercise and the learning effect was minimized.     

Effects of ischaemic training on force development and fibre-type composition in human skeletal muscle

Summary. Force (peak torque) of m. quadriceps femoris was measured during 60 repeated, voluntary dynamic knee extensions in 10 men before and after a 4-week training regimen of one-legged cycle exercise. Biopsies for histochemical analysis were obtained from the lateral vastus muscle after the training period. One leg was trained with the blood flow to the leg muscles reduced by local supra-atmospheric external pressure of 50 mmHg (‘Ischaemic leg, I-leg’). Employing the same work-load profile the other leg was trained at normal atmospheric pressure (‘Non-restricted-flow leg, N-leg’). In response to I-training, Maximum Peak Torqued (MPT; the highest torque produced in any contraction) and Initial Peak Torque (IPT; the average peak torque of the initial 12 contractions) decreased by 8% (P<0.01) and 9% (P<0.001), respectively. Final Peak Torque (FPT; the average peak torque of the final 12 contractions) increased by 13% (P<0.05) after I-training. No changes in MPT, IPT or FPT occurred following N-training. After training the proportion of slow-twitch fibres was higher (P<0.05) and the mean slow-twitch fibre area was larger (P<0.05) in the I-than in the N-trained leg. The results indicate that blood flow-restricted training, in contrast to non-restricted-flow training, decreases maximum voluntary dynamic force, possibly by inducing an increase in the share of the muscle cross-sectional area consisting of slow-twitch fibres. That flow-restricted training improves maintenance of force during short-term local exercise may reflect ischaemically induced changes in the metabolic characteristics of skeletal muscle.     

Quantifying human muscle strength, endurance and fatigue

Physiologic methods have been developed to objectively quantify muscle strength, endurance, and fatigability. Isometric force and rectified/integrated electromyogram were simultaneously recorded during the three phases of a recording session: pre-fatigue, fatigue (1 min duration) and post-fatigue recovery (up to 10 min). Five parameters of muscle performance were computed: Maximum force (MF) exerted during isometric voluntary contraction (muscle strength); Force-time integral--area under force-time plot (endurance); Fatigue index (FI) (% reduction in MF); Neuromuscular efficiency (force/mV of EMG recruited), and Recovery time (RT). Normal values based on data from 20 normal subjects were determined for four muscles: index finger abductor, elbow flexors, knee extensors, and ankle dorsiflexors. Neuromuscular efficiency (NME) decreased significantly (20 to 70%) at the end of the fatigue phase; it generally increased to the pre-fatigue level in 2 to 10 min, during the recovery phase. The period needed to reach pre-fatigue level was referred to as RT. The elbow flexors had the highest mean FI (48%) and the longest RT (greater than 6 min); the ankle dorsiflexors had the lowest mean FI (34%) and the shortest RT (1.5 min). These methods have been used also to evaluate the effects of weight training in two patients with neuromuscular disorders.     

骨骼肌细胞凋亡的影响因素:低氧训练效应

在外界低氧环境的刺激下,骨骼肌细胞易处于缺氧状态,这种缺氧趋势与细胞凋亡存在着某种直接或者间接的联系.在一定强度的运动中,机体的组织和细胞处于一种相对缺血和缺氧的状态,肌肉细胞内氧分压降到很低水平时,在骨骼肌组织中也能检测到细胞凋亡的发生.但有关低氧训练对骨骼肌细胞凋亡的影响目前尚未见报道,低氧训练对骨骼肌细胞凋亡会产生何种影响,骨骼肌细胞凋亡与不同低氧训练刺激时间和方式的关系如何,有必要进行深入研究和探讨.     

骨骼肌萎缩的细胞分子机制与抗萎缩运动模式

目的:回顾骨骼肌萎缩细胞分子机制的研究进展,抗萎缩运动模式和药物干预对骨骼肌萎缩的疗效及机制。资料来源:应用计算机检索PubMed数据库1988-03/2007-03相关骨骼肌萎缩的文献,检索词"skeletal muscle,atrophy,exercise,ubiquitin-proteasome,apoptosis",限定文献语言种类为英文。同时计算机检索万方数据库2002-03/2005-05相关骨骼肌萎缩的文献,检索词"骨骼肌,细胞凋亡,运动",限定文章语言种类为中文。资料选择:对资料进行初审,选取包括骨骼肌萎缩的文献,开始查找全文。纳入标准:涉及骨骼肌萎缩的蛋白质泛化、细胞凋亡、抗萎缩运动、药物干预的文章。排除标准:不涉及上述项目。资料提炼:共检索到61篇关于骨骼肌萎缩的文献,最终纳入33篇符合标准的文献。资料综合:骨骼肌萎缩有衰老性、废用性和病理性3种。去神经支配的动物模型有助于从细胞分子水平认识骨骼肌萎缩,蛋白质同化/泛化研究、细胞增殖/凋亡研究从不同角度揭示了骨骼肌萎缩的机制。废用性模型为开发抗萎缩药物和验证抗萎缩运动模式提供了研究平台,但尚缺少一致性结论,运动抵抗/延缓肌肉萎缩的效应体现于结构蛋白基因表达、细胞信号转导、激素、细胞因子等各个层面。在运动抗萎缩治疗中,药物与物理疗法的辅助作用也不可忽略。结论:骨骼肌萎缩的细胞分子机制与蛋白质泛化和细胞凋亡过甚密切相关,运动抵抗/延缓肌肉萎缩的效应体现于相应的细胞分子水平,药物和理疗对骨骼肌萎缩有一定疗效,但机制不明。     

Effects of strength and endurance training on muscle fibrecharacteristics in elderly women

The effects of 18weeks’ intensive strength and endurance training on fibre characteristics of the vastuslateralis muscle were studied in 76- to 78-year-old women. Type I and type IIa fibresconstituted over 90% of the cell population and were almost equally represented. Nochanges were observed in the proportions of the different fibre types. When comparing thebaseline and the 18-week measurements within the groups, the strength group showed a meanincrease of 34% (P=0·028) in mean type I fibre area. Thefrequency histograms showed an increased proportion of larger type I fibres after strengthtraining and a decreased proportion of smaller type IIa fibres after endurance training. In thecontrol subjects, the proportion of smaller type I and type IIa fibres increased during theexperimental period. The results indicate that intensive strength training induces type I fibrehypertrophy, whereas the effects of endurance training are less evident. The considerablevariation found in the change in muscle fibre cross-sectional areas is also noteworthy.     

Adaptation to exercise-induced muscle damage

1. Serum creatine kinase (CK) and muscle soreness, common indicators of muscle damage, were assessed in 16 subjects after performance of two bouts of eccentric exercise spaced 7 days apart. The purpose was (1) to examine rapid muscle adaptation when the ipsilateral limb was exercised on the second bout and (2) to investigate possible central adaptations when the contralateral limb was exercised on the second bout. 2. The LSL group (n = 7) and the LOL group (n = 9) performed the exercise with the ipsilateral and the contralateral limb, respectively. Careful attention was paid to stabilization of the subject so that the contralateral limb was not active in isometric stabilization. 3. For the LSL group, a lower CK and soreness response was found on about 2 compared with bout 1. For the LOL group, no significant difference in CK response and soreness was found between bout 1 and bout 2. 4. No repeat bout effect was found when the contralateral limb was exercised; therefore central adaptation from performance of the first exercise was minimal. Because a lower repeated bout effect was found after bout 2 using the ipsilateral limb, it was concluded that an experimental design using ipsilateral muscle groups should provide a good model to study rapid muscle adaptation to exercise damage.