穿戴腿部压缩套未能缓解下坡跑肌肉损伤和臂踝脉搏波速度

为了探讨下坡跑运动时穿戴腿部压缩套对运动后诱发肌肉损伤及动脉硬化指标-臂踝脉搏波速(brachial-ankle pulse wave velocity, baPWV)的影响,本研究选择12名无规律运动习惯的男性大学生,采用随机方式于运动中单腿穿戴腿部压缩套(实验腿),以另一腿为对照腿,接受一次70%保留心率(70%HRR)强度,坡度为-10°30 min原跑步机下坡跑运动,并于下坡跑运动前(前测)及下坡跑运动后24 h (后测)分别进行因变量的检测,检测项目包含肌酸激酶、baPWV、酸痛指数、主动关节活动度、肌肉肿胀围、最大自主等长收缩肌力及超声波股直肌肌肉厚度。本研究表明:下坡跑运动后24 h的CK值((467.08±229.64) U/L)显著高于前测((240.92±189.67) U/L)(p0.05);baPWV在实验处理及时间因子的交互作用未达显著,仅时间因子显示后测的baPWV ((1 110.71±51.30) cm/s)显著高于前测((1 042.92±38.17) cm/s)(p0.05);酸痛指数、主动关节活动度、肌肉肿胀围、最大自主等长收缩肌力及超声波股直肌肌肉厚度等在实验处理及时间因子亦无交互作用,且实验处理主要效果亦无显著性(p0.05)。本研究初步得出结论,穿戴腿部压缩套并无法减缓下坡跑运动所引起的肌肉损伤,及随后的延迟性肌肉酸痛与暂时性的baPWV上升现象。     

小球藻摄入干预对抗阻运动诱发的肌肉损伤的影响

为探究小球藻摄入干预对抗阻运动诱发的肌肉损伤的影响,本研究招募32名排球运动员为受试者,进行随机对照双盲实验设计,分别随机分为安慰剂组(n=16)与小球藻组(n=16),每位受试者以4.5 g/d的剂量连续服食小球藻或安慰剂35 d,进行单次抗阻运动以诱发肌肉损伤,损伤模式以85%最大肌力为负荷进行大腿蹬卧推、大腿曲屈、卧推3个动作各进行4组,每组动作重复8次。在摄入小球藻或安慰剂前,运动后24 h,运动后48 h分别测量血清肌酸激酶和乳酸脱氢酶活性,以量表评估肌肉疼痛程度,并在运动后第3天、第4天、第5天测量最大肌力表现。研究发现,抗阻运动造成血液肌酸激酶活性与肌肉酸痛感增加,肌肉力量降低;小球藻组运动后第24 h和第48 h血液肌酸激酶活性与肌肉酸痛感显著低于安慰剂组;小球藻组运动后3～4 d大腿推蹬力量显著高于安慰剂组,运动后4～5 d大腿曲屈与卧推力量显著高于安慰剂组。研究表明,小球藻摄入干预可以改善抗阻运动诱发的肌肉损伤,避免运动后的肌肉疲劳,同时降低恢复期的肌肉损伤。     

就离心收缩机制存在的问题探讨肌丝滑行理论的修正

按照肌纤维收缩时长度的变化,可将骨骼肌收缩分为向心(长度变短)、等长(长度不变)和离心(长度变长)收缩。与前两种收缩形式相比,离心收缩在增加肌肉体积和肌力等方面具有明显的优势[1,2],偏重于离心收缩的运动方式作为训练手段已广泛应用于竞技体育和运动康复领域[1–3]。然而,离心收缩很容易对骨骼肌的结构和功能造成负面影响,出现超微结构改变(如肌节、Z盘损伤),引起肌肉酸痛、肿胀和肌力下降等损伤症状[1,4,5]。     

低强度激光治疗对游泳大鼠氧化应激和功能恢复的影响

本研究的目的是确定低强度激光疗法(LLLT)联合有氧运动对机体氧化应激和心肺功能恢复的影响。本研究测试了60只SD大鼠,将大鼠随机分为对照组、低强度激光治疗组、运动组和低强度激光治疗+运动组(n=15)。检测了各组大鼠有氧运动训练或低强度激光治疗6周后的最大摄氧量(VO_2max 0.75)和最大运动速度;检测了各组大鼠腓肠肌中过氧化氢酶(CAT)、超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GPx)和丙二醛(MDA)水平以及大鼠血清肌酸激酶(CK)、天冬氨酸转氨酶(AST)和丙氨酸转氨酶(ALT)水平。研究显示,低强度激光治疗+运动组大鼠的最大摄氧量和最大运动速度均显著高于其他组(p0.05)。低强度激光治疗+运动组的CAT、SOD和GPx活性均显著高于其他组(p0.05),而MDA水平显著低于其他组(p0.05)。低强度激光治疗+运动组的血清CK、AST和ALT水平均显著低于其他组(p0.05)。本研究表明在有氧运动基础上进行低强度激光治疗可有效提高机体的心肺功能,改善抗氧化防御系统,减少脂质过氧化损伤和运动损伤。     

连续摄入小球藻提取物缓解大鼠运动性心肌损伤研究

为探讨小球藻保护大鼠运动因运动造成的心肌损伤,为小球藻科学合理的应用和推广提供理论依据,本研究将60只SD大鼠随机分为5组:对照组(C组)、运动对照组(S组)、运动+低剂量小球藻组(SCL组)、运动+高剂量小球藻组(SCH组),每组12只大鼠。所有参与实验的大鼠每天自由饮水择食,小球藻的摄入采用灌胃器每日灌胃一次。小球藻各组灌胃体积为5 m L/kg,其他组灌入等量生理盐水。安静对照组(C组)笼内自由活动,不进行额外运动,运动对照组(S组)、运动+低剂量小球藻组(SCL组)、运动+高剂量小球藻组(SCH组)进行8周的跑台跑步训练,每周6次。1~4周进行中等强度训练,5~8周进行高强度训练。本研究发现,在大鼠血清谷丙转氨酶、乳酸脱氢酶、肌酸激酶、α-羟丁酸脱氢酶含量水平,S组较C组均显著升高(p<0.05)。血清谷丙转氨酶、乳酸脱氢酶、肌酸激酶含量,SCL组和SCH组显著低于S组(p<0.05),SCL组和SCH组组间无显著性差异(p>0.05),且随剂量增加而递减。鼠心肌SOD活性方面,S组显著低于C组(p<0.05);SCL组和SCH组显著高于S组(p<0.05),组间随剂量增加而递增;SCH组显著高于SCL组(p<0.05)。血清、心肌CGRP水平,S组显著低于C组(p<0.05);SCL组和SCH组显著低于S组均显著降低(p<0.05)。本研究认为摄入小球藻能够有效消除机体由于长期高强度大负荷运动下产生的过量的自由基;提高机体免疫力,增强血管原生性一氧化氮合酶活性。     

麝香保心丸对一次性力竭运动大鼠心肌损伤标记物和C反应蛋白的影响

目的探讨麝香保心丸对一次性力竭运动大鼠心肌损伤标记物和C反应蛋白的影响。方法选择雄性Wistar大鼠52只,随机分成实验组和对照组,每组26只。两组大鼠每天自由进食饮水相同,实验组大鼠每天麝香保心丸2粒(每粒22.5 mg)分2次灌胃,共两周。两组均接受力竭游泳运动,制成力竭运动动物模型,分别测定和比较两组大鼠血清和心肌组织肌酸激酶(CK)、肌酸激酶同工酶(CK-MB)、肌钙蛋白T(Tn T)、B型脑钠肽(BNP)和C反应蛋白(CRP)水平。结果大鼠平均力竭运动游泳时间实验组较对照组明显延长(P0.01)。实验组血清和心肌组织CK、CK-MB、Tn T、BNP和CRP水平均明显低于对照组(P0.05)。结论麝香保心丸可显著降低力竭运动大鼠血清和心肌中CK、CK-MB、Tn T、BNP和CRP水平,能够减轻力竭运动后心肌损伤。     

浮力负重增强式干预有助于改善2型糖尿病患者下肢运动表现

为探讨8周浮力负重增强式训练对腿部肌力、爆发力、动作稳定度、肌力保留效果的影响,本研究招募33名2型糖尿病患者受试者,在训练前1周进行前测(等速肌力60°/s和180°/s,摆臂垂直跳,动态稳定性),将33名受试者随机分成浮力负重增强训练组(buoyancy plyometric training group, B组)(n=11)、一般增强式训练组(plyometric training group, P组)、对照组(control group, C组)(n=11)。各组按照方案进行为期8周的训练干预,干预结束后进行后测,操作人员与内容与前测一致。本研究发现,等速肌力测试、爆发力测试、身体稳定性方面C组、B组和P组的前测结果相比无显著性差异(p0.05),说明前测组间差异不会对干预结果造成影响。经过8周运动干预后,B组和P组后测结果显著高于C组(p0.05),且P组后测结果显著高于B组(p0.05)。在停训4周后,B组和P组后测结果显著高于C组(p0.05)。而肌酸激酶方面,第2周至第6周内,C组肌酸激酶值显著低于B组和P组(p0.05),且B组肌酸激酶值显著高于P组(p0.05)。到第4周,P组肌酸激酶值显著低于第2周(p0.05);且P组第6周肌酸激酶值显著低于第8周(p0.05)。到第8周,P组与C组肌酸激酶值没有显著性差异(p0.05),B组显著高于C组(p0.05)。本研究认为浮力负重增强式训练能够增加2型糖尿病患者下肢肌力、下肢爆发力,并且可以显著改善下肢稳定性,且其效果优于在地面进行的增强式训练。浮力负重增强式训练后下肢肌力、爆发力、稳定性衰退速度缓慢,但其机制尚有待进一步研究。     

蛋白和抗氧化剂对离心运动后肌肉功能和疼痛的影响

大量研究证实补充蛋白质或抗氧化剂均可有效提高机体的运动能力,然而,蛋白质和抗氧化剂联用的效果尚不清楚。本研究将60只SD大鼠随机分为4组,安静组(CG)、运动组(EG)、蛋白组(PG)和蛋白+抗氧化剂组(PAG),每组15只。PG组大鼠按照0.5 g/kg的剂量灌胃乳清蛋白溶液,PAG组大鼠按照0.5 g/kg的剂量灌胃乳清蛋白和抗氧化剂(富含花青素的浆果提取物)溶液。CG和EG组大鼠灌胃等体积的蒸馏水,共灌胃1周。然后,EG、PG和PAG组大鼠进行90 min的离心运动。采用机械缩足阈值来反映各组大鼠离心运动后的肌肉酸痛程度,研究显示,离心运动48 h后,PG组和PAG组大鼠的机械缩足阈值明显高于EG组,并且PG组和PAG组高于PG组。多项研究均显示,IL-6、IL-1β、MG53和MyoD参与肌肉的损伤及修复过程。本研究检测了上述因子的变化情况,发现大鼠在离心运动48 h后,后胫骨前肌组织中IL-6、IL-1β、MG53和MyoD的蛋白表达水平均显著升高,而蛋白+抗氧化剂可显著抑制上述指标的升高。苏木精伊红(HE)染色显示,离心运动48 h后,运动组大鼠的肌纤维受损程度达39.43%,显著高于蛋白组(23.54%)和蛋白+抗氧化剂组(8.42%)。此外,蛋白和抗氧化剂可显著抑制离心运动诱导的血清肌酸激酶的升高,并提高超氧化物歧化酶的活性。本研究证实蛋白联合抗氧化剂可有效减少离心运动引起的肌肉损伤、抑制机体的炎症反应并降低肌肉酸痛程度。     

举重运动通过激活PI3K/Akt信号途径并促进肌肉卫星细胞活化来改善肌肉功能

为了考察举重运动对卫星细胞活化和PI3K/Akt信号通路的影响,本研究将60只SD大鼠随机分为对照组(未进行运动)、耐力运动组和举重运动组。耐力运动组和举重运动组大鼠分别进行8周相应的运动。采用双重免疫荧光染色检测大鼠骨骼肌组织中活化的卫星细胞数(Pax7+/MyoD+)。采用Western blotting检测大鼠骨骼肌组织中Akt、mTOR、p70S6K、4E-BP1、IL-1β和IL-6的表达。采用苏木精和曙红(HE)染色评价骨骼肌形态。采用日立7060全自动生化分析仪检测大鼠血清肌酸激酶(CK)水平。采用邻苯三酚比色法检测血清超氧化物歧化酶(SOD)活性。研究发现,运动后,举重运动组活化的卫星细胞数显著高于耐力运动组。运动后,举重运动组的Akt、mTOR、p70S6K和4E-BP1的磷酸化水平显著高于耐力运动组,而IL-1β和IL-6蛋白表达水平显著低于耐力运动组。运动后,举重运动组的血清CK水平显著低于耐力运动组,而SOD水平显著高于耐力运动组。本研究表明举重运动可促进肌肉卫星细胞的活化并且激活PI3K/Akt信号通路及下游分子。此外,举重运动还可提高机体抗氧化能力并预防炎症损伤。     

下坡跑后大鼠腓肠肌成肌调节因子的变化

目的:探讨成肌调节因子(MyoD)在肌肉损伤修复过程中的动态表达,为促进运动肌肉损伤的再生修复提供实验依据。方法:将健康雄性2月龄SD大鼠80只,随机分为对照组(n=10)和下坡运动组(n=70),下坡运动组再分为运动后即刻组、12h、24h、48h、72h、7d和14d组,各运动组动物均进行持续性下坡跑,分别在运动结束后8个时间点麻醉,下腔静脉取血,分离血清,取双侧腓肠肌。常规检测CK、LDH的活性。采用免疫组织化学染色法以及计算机图像分析技术定量统计MyoD因子表达情况。结果:血清CK、LDH在运动后即刻显著上升,后逐渐下降至正常水平。成肌调节因子MyoD在正常骨骼肌中即有表达,各运动组大鼠腓肠肌MyoD因子表达较对照组均有增加,48h组大鼠腓肠肌MyoD免疫阳性细胞核数明显多于对照组(P0.05),后随时间逐渐下降。结论:离心运动后即刻MyoD的表达水平开始上升,48h达到峰值,随后逐渐下降至正常水平。提示成年早期大鼠(2月龄)已具备较成熟的肌肉再生修复能力。     

Comparison of responses to strenuous eccentric exercise of the elbow flexors between resistance-trained and untrained men

This study compared resistance-trained and untrained men for changes in commonly used indirect markers of muscle damage after maximal voluntary eccentric exercise of the elbow flexors. Fifteen trained men (28.2 +/- 1.9 years, 175.0 +/- 1.6 cm, and 77.6 +/- 1.9 kg) who had resistance trained for at least 3 sessions per week incorporating exercises involving the elbow flexor musculature for an average of 7.7 +/- 1.4 years, and 15 untrained men (30.0 +/- 1.5 years, 169.8 +/- 7.4 cm, and 79.9 +/- 4.4 kg) who had not performed any resistance training for at least 1 year, were recruited for this study. All subjects performed 10 sets of 6 maximal voluntary eccentric actions of the elbow flexors of one arm against the lever arm of an isokinetic dynamometer moving at a constant velocity of 90 degrees .s. Changes in maximal voluntary isometric and isokinetic torque, range of motion, upper arm circumference, plasma creatine kinase activity, and muscle soreness before, immediately after, and for 5 days after exercise were compared between groups. The trained group showed significantly (P < 0.05) smaller changes in all of the measures except for muscle soreness and faster recovery of muscle function compared with the untrained group. For example, muscle strength of the trained group recovered to the baseline by 3 days after exercise, where the untrained group showed approximately 40% lower strength than baseline. These results suggest that resistance-trained men are less susceptible to muscle damage induced by maximal eccentric exercise than untrained subjects.     

Effects of baseline serum levels of Se on markers of eccentric exercise-induced muscle injury

Inflammation and oxidative stress have been implicated in the mechanism of eccentric exercise-induced muscle injury. This study examined whether baseline serum levels of selenium (Se), a trace element that participates in both antioxidant and anti-inflammatory systems, affects the overall response to injury. Thirteen males performed 36 maximal eccentric actions with the elbow flexors of the non-dominant arm on a motorized dynamometer. Venous blood samples were collected immediately before and after exercise at 2, 24, 48, 72 and 96 hours. Established indicators of muscle damage such as maximum isometric torque (MIT), range of motion (ROM), relaxed arm angle (RANG), flexed arm angle (FANG), arm circumference (CIRC), muscle soreness and serum levels of creatine kinase (CK) and lactate dehydrogenase (LDH) were determined at the same time points. Baseline serum levels of Se were also measured. Complementary data regarding assessment of Se status were retrieved by the use of a semi-quantitative food frequency questionnaire. All measures changed significantly (p<0.05) after exercise. The main finding of this study was that baseline Se serum levels were associated inversely with CK, LDH and FANG and positively with MIT and ROM (p<0.05). These data suggest that beyond overt Se deficiency, suboptimal Se status possibly worsens muscle functional decrements subsequent to eccentric muscle contractions.     

Effects of deep heat as a preventative mechanism on delayed onset muscle soreness

The effects of increased muscle temperature via continuous ultrasound prior to a maximal bout of eccentric exercise were investigated on the symptoms of delayed onset muscle soreness (DOMS) of the elbow flexors. Perceived muscle soreness, upper arm circumferences, range of motion (ROM), and isometric and isokinetic strength were measured over 7 days on 14 college-aged men (n = 6) and women (n = 8). Ten minutes of continuous ultrasound (ULT) or sham-ultrasound (CON) were administered. Muscle temperature was measured in the biceps brachii of both arms. Muscle temperature increased by 1.79 degrees +/- 0.49 degrees C (mean +/- SD) in the experimental arm of the ULT group. Muscle soreness was induced by a single bout of 50 maximal eccentric contractions. The ULT group did not differ significantly (p < 0.05) from the CON group with respect to perceived muscle soreness, upper arm circumference, ROM, and isometric and isokinetic strength. In conclusion, increased muscle temperature failed to provide significant prophylactic effects on the symptoms of DOMS.     

Difference in the magnitude of muscle damage between maximal and submaximal eccentric loading

This study compared maximal (MAX-ECC) and submaximal (50%-ECC) eccentric exercise of the elbow flexors. Untrained male students (n = 8) performed 3 sets of 10 repetitions of MAX-ECC with one arm and 50%-ECC with the other arm, separated by 4 weeks. In MAX-ECC, the elbow joint was forcibly extended from a flexed (90 degrees ) to a full-extended position (180 degrees ) in 3 seconds while producing maximal force. For 50%-ECC, a dumbbell set at 50% of the maximal isometric strength at 90 degrees of the elbow joint was lowered from the flexed to the extended position in 3 seconds. Changes in indicators of muscle damage were compared between the bouts by a 2-way repeated-measures analysis of variance. Changes in isometric strength, range of motion, upper arm circumference, and plasma creatine kinase activity were significantly smaller and the recovery was significantly faster for 50%-ECC compared with MAX-ECC, although the differences in the changes immediately after exercise were small. It appeared that the magnitude of initial muscle damage was similar between the bouts; however, secondary damage was less after 50%-ECC.     

Neuromuscular dysfunction with the experimental arm acting as its own reference following eccentric and isometric exercise

Eccentric exercise has been extensively used as a model to study muscle damage-induced neuromuscular impairment, adopting mainly a bilateral matching task between the reference (unexercised) arm and the indicator (exercised) arm. However, little attention has been given to the muscle proprioceptive function when the exercised arm acts as its own reference. This study investigated muscle proprioception and motor control, with the arm acting both as reference and indicator, following eccentric exercise and compared them with those observed after isometric exercise. Fourteen young male volunteers were equally divided into two groups and performed an eccentric or isometric exercise protocol with the elbow flexors of the non-dominant arm on an isokinetic dynamometer. Both exercise protocols induced significant changes in indicators of muscle damage, that is, muscle soreness, range of motion and maximal isometric force post-exercise (p < 0.05–0.001), and neuromuscular function was similarly affected following both protocols. Perception of force was impaired over the 4-day post-exercise period (p < 0.001), with the applied force being systematically overestimated. Perception of joint position was significantly disturbed (i.e., target angle was underestimated) only at one elbow angle on day 4 post-exercise (p < 0.05). The misjudgements and disturbed motor output observed when the exercised arm acted as its own reference concur with the view that they could be a result of a mismatch between the central motor command and an impaired motor control after muscle damage.     

Repeated eccentric exercise bouts do not exacerbate muscle damage and repair

This study examined whether performing repeated bouts of eccentric exercise 2 and 4 days after an initial damaging bout would exacerbate muscle damage. One arm performed 3 sets of 10 eccentric actions of the elbow flexors (ECC1) using a dumbbell set at 50% of the maximal isometric force at 90 degrees (SINGLE). Two weeks later the same exercise was performed by the opposite arm with the exception that subsequent bouts were performed 2 (ECC2) and 4 (ECC3) days after ECC1 (REPEATED). In the REPEATED condition, maximal isometric force (MIF) decreased to the same level immediately after ECC1-3, and the decreases in range of motion (ROM) and increases in upper arm circumference immediately postexercise were similar among the bouts. However, no significant differences in changes in MIF, ROM, muscle soreness, and plasma creatine kinase activity were evident between the SINGLE and REPEATED conditions when excluding the changes immediately after ECC2 and ECC3. These results suggest that ECC2 and ECC3 did not exacerbate muscle damage or affect the recovery process.     

Intensity of eccentric exercise, shift of optimum angle, and the magnitude of repeated-bout effect.

This study compared the effect of four different intensities of initial eccentric exercise (ECC1) on optimum angle shift and extent of muscle damage induced by subsequent maximal eccentric exercise. Fifty-two male students were placed into 100%, 80%, 60%, or 40% groups (n = 13 per group), performing 30 eccentric actions of the elbow flexors of 100%, 80%, 60%, or 40% of maximal isometric strength [maximal voluntary contraction (MVC)] for ECC1, followed 2-3 wk later by a similar exercise (ECC2) that used 100% MVC load. MVC at six elbow joint angles, range of motion, upper arm circumference, serum creatine kinase activity, myoglobin concentration, and muscle soreness were measured before and for 5 days following ECC1 and ECC2. A rightward shift of optimum angle following ECC1 was significantly (P < 0.05) greater for the 100% and 80% than for the 60% and 40% groups, and it decreased significantly (P < 0.05) from immediately to 5 days postexercise. By the time ECC2 was performed, only the 100% group kept a significant shift (4 degrees). Changes in most of the criterion measures following ECC1 were significantly greater for the 100% and 80% groups compared with the 60% and 40% groups. Changes in the criterion measures following ECC2 were significantly (P < 0.05) greater for the 40% group compared with other groups. Although the magnitude of repeated bout effect following ECC2 was significantly (P < 0.05) smaller for the 40% and 60% groups, all groups showed significantly (P < 0.05) reduced changes in criterion measures following ECC2 compared with the ECC1 100% bout. We conclude that the repeated-bout effect was not dependent on the shift of optimum angle.     

Effects of a protease supplement on eccentric exercise-induced markers of delayed-onset muscle soreness and muscle damage

This investigation examined the effects of a protease supplement on selected markers of muscle damage and delayed-onset muscle soreness (DOMS). The study used a double-blinded, placebo-controlled, crossover design. Twenty men (mean +/- SD age = 21.0 +/- 3.1 years) were randomly assigned to either a supplement group (SUPP) or a placebo group (PLAC). All subjects were tested for unilateral isometric forearm flexion strength, hanging joint angle, relaxed arm circumference, subjective pain rating, and plasma creatine kinase activity and myoglobin concentration. The testing occurred before (TIME1), immediately after (TIME2), and 24 (TIME3), 48 (TIME4), and 72 (TIME5) hours after a bout of eccentric exercise. During these tests, the subjects in the SUPP group ingested a protease supplement. The subjects in the PLAC group took microcrystalline cellulose. After testing at TIME5 and 2 weeks of rest, the subjects were crossed over into the opposite group and performed the same tests as during visits 1-5, but with the opposite limb. Overall, isometric forearm flexion strength was greater (7.6%) for the SUPP group than for the PLAC group, despite nearly identical (difference = 0.14 N.m, p = 0.940) mean strength values before (TIME1) the eccentric exercise protocol. There were no between-group differences for hanging joint angle, relaxed arm circumference, subjective pain ratings, and plasma creatine kinase activity and myoglobin concentration from TIME1 to TIME5. These findings provided initial evidence that the protease supplement may be useful for reducing strength loss immediately after eccentric exercise and for aiding in short-term strength recovery. The protease supplement had no effect, however, on the perception of pain associated with DOMS or the blood markers of muscle damage.     

Exercise-induced muscle damage: effects of light exercise on damaged muscle.

The effects of performing light eccentric exercise (LB) during the period of recovery from a heavy eccentric exercise bout (HB) were studied. An experimental and a control group, each consisting of nine college age volunteers (seven women, two men) performed two HB--HB1 and HB2--14 days apart, using the elbow flexor and extensor muscles of one arm. The experimental group performed an additional LB on the day following the first HB. HB1 resulted in muscle soreness, muscle weakness, changes in elbow joint flexibility, and large delayed increases in serum creatine kinase (CK) activity. The HB2 produced smaller changes in all parameters, indicating that adaptation to the effects of eccentric exercise had occurred in the muscle. The LB did not alter muscle soreness, strength or elbow flexibility, but did reduce or delay CK activity increase after HB1. The LB had no apparent effect on adaptation to HB2.     

Responses of elbow flexors to two strenuous eccentric exercise bouts separated by three days

This study investigated whether the second eccentric exercise performed 3 days after the initial bout would exacerbate muscle damage and retard the recovery. Fifty-one athletes performed 30 eccentric actions of the elbow flexors using a dumbbell weighted 100% of the maximal isometric force (MIF) at the elbow joint angle of 90 degrees (ECC1). Three days after ECC1, all subjects except those in the control group (n = 12) performed the second bout (ECC2) with the same (100%) intensity (n = 12), 90% (n = 13), or 80% (n = 14) of the ECC1. Some subjects, especially in the 100% group, required spotting for ECC2 but made maximal effort to complete the exercise. MIF, range of motion, upper-arm circumference, muscle soreness, muscle proteins in the blood, and ultrasound images were used to assess muscle damage. Changes in these measures for 9 days following ECC1 were compared among groups by 2-way analysis of variance (ANOVA) with repeated measures. All criterion measures changed significantly after ECC1; however, no significant differences between the groups were evident for any of the changes in the measures. These results suggest that it is possible for athletes to complete the second bout if the intensity is reduced 10-20% from the initial bout. No significant differences between the control group and other groups indicate that the second eccentric exercise performed 3 days after the initial bout does not exacerbate muscle damage and retard the recovery regardless of the intensity of the second bout. It is concluded that the elbow flexors can perform high-intensity eccentric exercise in the early stage of recovery from the initial bout and are not damaged further by performing a subsequent bout 3 days after the first.