蜜蜂春季增长阶段饲料适宜蛋白质水平的研究

早春将群势、蜂王年龄和质量基本一致的30群意大利蜜蜂Apis mellifera ligustica Spinola,随机分为5个处理组和1个对照组。处理组分别饲喂蛋白质水平为20%、25%、30%、35%和40%的5种代用花粉饲料,对照组饲喂油菜花粉,观测饲料蛋白质水平对蜂群群势、取食量、初生重以及蜂体组织蛋白含量的影响。结果表明对照组中蜜蜂对油菜花粉的取食量最高,但仅显著高于蛋白质水平为40%的饲料(P<0.05);蛋白质水平为25%、30%、35%的处理组群势增长差异不显著(P>0.05),但均显著高于对照组(P<0.05);随着饲料蛋白质水平升高,工蜂初生重逐渐升高,在35%到达最高值,随后又下降;饲喂蛋白质水平为20%、25%、30%饲料的蜂体组织蛋白含量与对照组差异不显著(P>0.05),饲喂蛋白质水平为35%、40%饲料的蜜蜂体组织蛋白含量显著高于对照组(P<0.05)。     

温度对花背蟾蜍心电活动影响的多元回归分析模型

运用多元回归分析方法对花背蟾蜍(Buforaddei)在4个不同实验温度条件下描记的心电图实验数据,利用SPSS/PC 统计分析的软件包进行处理分析,结果表明蟾蜍的心率和心电图各指标有显著相关性;温度对蟾蜍的心电活动影响较明显;随着温度的升高,蟾蜍心率,P波、R波、T波电压值升高;P-T间期,Q-T间期,QRS间期值均显下降趋势。     

世居高原健康成人逐级递增负荷运动测试心率拐点与乳酸恢复能力、肺功能的相关性*

目的:探讨世居3 200 m高原环境下20～40岁健康人群逐级递增负荷运动测试(Conconi)心率拐点(HRDP)与乳酸恢复能力、肺功能关联性。方法:以225名世居3 200 m高原的20～40岁健康人群为研究对象,按照年龄区分为20～25岁组(男26,女25)、26～30岁组(男32,女28)、31～35岁组(男29,女33)及36～40岁组(男22,女30),通过改良后Conconi测试前、测试中及测试后恢复期心率、血乳酸变化规律评价机体HRDP强度、心率恢复能力及血乳酸恢复能力。结果:①受试者心率水平随运动强度提高呈上升趋势,且运动后恢复期心率水平呈现下降趋势,世居高原男性Conconi测试中心率水平显著低于女性(P＜0.05);同年龄阶段下,男性HRDP出现较晚,女性HRDP出现较早;同性别阶段下,男性组随年龄上升HRDP出现时间提前,女性组该现象不显著;HRDP_speed随年龄上升存在下降趋势。②随年龄上升,受试者血乳酸拐点浓度逐渐降低,但低年龄组与高年龄组间不存在显著差异;男性Conconi测试中血乳酸水平显著低于女性(P＜0.05)。③随年龄上升各性别组FVC、MVV、FEV1及FEV1/FVC水平均呈下降趋势,男性组以上各数据均显著高于同年龄段女性组(P＜0.05)。④负荷-心率曲线及心率-血乳酸拟合曲线显示,男性组相关系数依次为0.8345、0.8954、0.8680及0.8892;女性组相关系数依次为 0.9318、0.9661、0.9663及0.9599。各性别、年龄组HRDP值均与其MVV水平存在显著关联(P＜0.05),除男性组36-40岁受试者外,其余各性别、年龄组肺功能与乳酸消除速率亦存在显著关联(P＜0.05)。结论:世居3 200 m高原20～40岁健康人群运动心率反应规律及呼吸系统机能存在年龄及性别差异,HRDP与乳酸恢复能力、肺功能间存在显著关联,上述指标可以作为评估世居高原健康成人有氧运动耐力能力的有效手段。     

电刺激迷走神经对蟾蜍心率和心率变异的影响

目的:观察不同频率迷走神经刺激对蟾蜍离体心脏的心率及心率变异的影响。方法:将蟾蜍心脏和右侧迷走交感干离体后,以不同频率电刺激神经,记录心电图曲线并作心率变异性(HRV)分析。结果:交感神经阻断后,电刺激迷走交感干,心率(HR)显著下降(P0.01),全部正常心动周期的标准差(SDNN)和相邻正常心动周期差值的均方根(RMSSD)显著升高(P0.01),不同频率刺激组之间没有明显差异;与对照组相比,各指标变化较大;给药组0.2Hz时高频(HF)显著升高(P0.01),低频/高频比值(LF/HF)明显降低(P0.05),0.8Hz时HF和LF/HF接近刺激前水平。结论:一定范围内增加刺激频率,迷走神经降低心率的作用增强;没有交感神经调节条件下的迷走神经对心率和心率变异的调节可能存在不同的机制。     

温度和水分及盐分胁迫对银沙槐种子萌发的影响

利用控制实验研究了温度、湿度、干旱和盐分胁迫等生态因子对银沙槐种子萌发的影响,以探索银沙槐种子对各种生态因子的适应性。结果显示:(1)银沙槐种子在20℃、25℃恒温和15℃/25℃、20℃/30℃、10℃/20℃变温环境中的发芽率较高且无显著差异,其在20℃恒温、15℃/25℃、20℃/30℃变温条件下的发芽指数较高,但差异不显著。(2)土壤含水量在1%～5%之间,各水分处理间种子发芽率差异显著(P<0.05),而在5%～25%间种子发芽率变化不显著。(3)盐胁迫和水分胁迫对银沙槐种子的萌发均有明显的抑制作用,可显著降低种子萌发率(P<0.05);种子发芽指数和活力指数均随渗透势和NaCl浓度增大而显著减小(P<0.05);恢复萌发率随渗透势和NaCl浓度的增加而显著增加(P<0.05)。研究发现,银沙槐种子萌发最适温度为20℃恒温和15℃/25℃变温,最适土壤含水量为10%～25%;种子萌发对盐分和干旱胁迫表现出不同程度的耐受性,萌发过程中主导抑制因素为渗透胁迫,离子毒害作用甚微;银沙槐种子休眠机制和萌发特征表现出它对生境的良好适应性。     

阿司匹林对离体蟾蜍心功能影响的实验研究

目的:观察阿司匹林(aspirin)溶液对离体蟾蜍心脏心率和心肌收缩力的影响。方法:根据斯氏蛙心插管方法,用不同浓度的阿司匹林对离体蟾蜍心脏进行灌流,采用BL-410生物机能实验系统记录心率和心肌收缩力的变化。结果:灌注0.1g/ml的阿司匹林溶液时,离体蟾蜍的心脏收缩力明显下降和心率明显减慢(P0.05),心脏甚至停止跳动,0.05g/ml的阿司匹林溶液时,离体蟾蜍的心脏收缩力降低和心率减慢程度不如0.1g/ml,并且随着阿司匹林浓度的降低离体蟾蜍的心脏收缩力和心率降低程度逐渐较少。结论:阿司匹林溶液降低离体蟾蜍心肌收缩力和减慢心率,并随着阿司匹林浓度升高,其心肌收缩力和心率降低程度更加明显。     

温、光、盐对三角褐指藻紫外诱变株生长、总脂及脂肪酸的影响

为了优化微藻培养条件,采用单因子试验研究了不同温度(10、15、20、25、30℃)、不同光照强度(20、40、60、80、100、120μmol·m-2·s-1)和不同盐度(5、10、15、20、25、30、35、40)对三角褐指藻紫外诱变株MP-2的影响。结果表明:温、光、盐对MP-2的生长、总脂含量和脂肪酸组成影响显著(P0.05)。MP-2生长和总脂积累的适宜温度为10~25℃,最适20℃;低温有利于EPA和PUFA的积累,15℃时EPA(30.94%)和PUFA(39.53%)较高;MP-2生长的适宜光照强度为20~120μmol·m-2·s-1,最适光强为40μmol·m-2·s-1,低光强有利总脂的积累,光照强度为20~40μmol·m-2·s-1时总脂含量(25.81%~25.26%)较高;光强对PUFA和EPA的积累影响显著(P0.05),光照强度100μmol·m-2·s-1时EPA高达29.15%,光照强度80~100μmol·m-2·s-1时PUFA高达40.22%~40.56%;MP-2生长的适宜盐度为10~40,最适盐度25,高盐有利总脂的积累,盐度30~35时总脂含量高达36.54%~36.66%,低盐有利EPA和PUFA积累,盐度为10~15时EPA高达31.31%~31.46%,盐度15时PUFA最高(44.75%)。     

不同蛋白质和脂肪水平对1龄团头鲂生长性能和体组成的影响

试验采用3×3因子设计,探讨了饲料中不同蛋白质和脂肪水平对1龄团头鲂[均重:(50.37±1.27)g]生长性能和体组成的影响。试验设3个蛋白质水平(25%、30%和35%)和3个脂肪水平(3%、6%和9%),共配制9组饲料。试验鱼饲养于网箱(规格为2 m×1 m×1 m)中,每天投喂3次,试验期为8周。结果表明:蛋白质和脂肪之间无交互作用存在(P>0.05)。蛋白质和脂肪水平对存活率无显著影响(P>0.05)。增重率、特定生长率和饵料系数显著受蛋白质和脂肪水平影响(P<0.05)。其中,25%蛋白组的增重率及特定生长率显著低于其他蛋白组(P<0.05),而6%脂肪组显著高于其他脂肪组(P<0.01)。尽管35%蛋白6%脂肪组的饵料系数最低,但与除了25%蛋白3%脂肪和25%蛋白9%脂肪这两组外的其他组相比,差异均不显著(P>0.05)。蛋白效率比和氮保留率随蛋白质水平的升高显著降低(P<0.05)。此外,蛋白效率比显著受脂肪水平的影响(P<0.05),以6%组最高。能量保留率随脂肪水平的升高显著升高(P<0.05)。鱼体肥满度随蛋白质和脂肪水平的升高显著升高(P<0.05)。腹脂率和肝体比随脂肪水平的升高显著升高(P<0.05),而受蛋白质水平的影响较小(P>0.05)。蛋白质水平对全鱼、胴体和肝脏的组成均无显著影响(P>0.05)。脂肪水平对全鱼水分、脂肪和能量有极显著影响(P<0.01),其中,全鱼水分含量随脂肪水平的升高显著降低(P<0.01),而脂肪和能量含量则显著升高(P<0.01)。胴体和肝脏水分、脂肪含量的变化趋势与全鱼基本一致。以上结果表明,1龄团头鲂的适宜蛋白质和脂肪水平分别为30%和6%,适宜蛋能比为18.21 g/MJ。     

免耕对玉米根系属性和产量以及土壤物理性质的影响:整合分析

探讨免耕对作物根系生长和产量以及土壤物理性质的影响可以为科学管理保护性耕作提供依据。本文对相关文献进行整合分析发现,免耕显著降低玉米根长、根长密度和根表面积,降幅分别为13.8%、15.7%和22.8%,而免耕对玉米根系生物量、生物量密度和比根长影响不显著;免耕显著降低了玉米产量,降幅达8.4%,并与土壤p H有关(pH7.0,P0.05; pH≥7.0,P0.05)。免耕显著增加土壤容重和穿透阻力,增幅为3.5%、13.0%;减少了土壤含水量。沿土壤剖面,免耕对生物量密度的影响从负效应(10～20 cm,-22.2%)、无影响(0～10 cm和20～30 cm,P0.05)到正效应(30～40 cm,33.3%),而对生物量密度在水平分布上无影响;免耕显著增加了土壤容重(0～20 cm)和穿透阻力(0～10 cm)。鉴于免耕对玉米产量和土壤物理环境的负效应,建议实践中由常规耕作转变为免耕后同时结合秸秆覆盖(或还田)策略,未来应加强研究作物根系属性对保护性耕作的响应与适应机制,以及免耕/秸秆还田等多策略的长期观测试验研究,为农业可持续发展提供理论和实践参考。     

不同林龄桤-柏混交林生态系统的碳储量及其分配

选取代表性的10、15、20和25年生桤(Alnus cremastogyne)柏(Cupressus funebris)混交林及由桤-柏混交林演替而来的30年生纯柏林为研究对象, 探讨了川中丘陵区人工桤-柏混交林生态系统碳储量的变化动态及其分配规律.结果表明：桤-柏混交林的植被碳储量在10～30年间持续增加,30年时达到52.40 t·hm^-2,5个林龄中乔木层碳储量所占比例均在85.59%以上;桤-柏混交林的土壤碳储量(0～40 cm)在10～15年间显著增加(P<0.05),15年时达最大值84.79 t·hm^-2,15～25年间显著下降(P<0.05),25～30年间趋于稳定(P>0.05);桤-柏混交林生态系统碳储量在15年时达最大值118.13 t·hm^-2,15～25年间缓慢下降,25～30年间有所增加;植被碳储量所占比例在10～30年间持续增加,土壤碳储量则相反.与我国其他类型人工林相比,桤-柏混交林的碳储量偏低.     

Acidosis counteracts the negative inotropic effect of K+ on ventricular muscle strips from the toad Bufo marinus

Strenuous activity is associated with acidosis, increased extracellular potassium concentration ([K+]o), and elevated levels of circulating catecholamines. Acidosis and elevated [K+]o are normally considered harmful to cardiac function, and a high sympathetic tone on the heart may lead to arrhythmia. During activity, however, the heart must be able to increase rate and strength of contraction. While the individual effects of [K+]o, acidosis, and adrenaline on contractile properties of cardiac muscle have been characterized for some ectothermic species, less information is available on their interactions. Here we examine the isolated and combined effects of [K+]o, acidosis, and adrenaline on ventricular muscle strips from the toad Bufo marinus. This study showed that increased [K+]o significantly reduced twitch force, while lactic acid significantly increased twitch force and more than counteracted the negative inotropic effects of elevated [K+]o. There was no inotropic effect of Na-lactate (neutralized lactic acid), which suggests that lactic acid stimulated twitch force through reduced pH and not by serving as a substrate. Adrenaline had a positive effect on twitch force in all preparations. Irrespective of treatment, twitch force decreased as stimulation rate increased. During high [K+]o, there was a severe reduction in maximal frequency of toad ventricular strips that was not alleviated by lactic acidosis and/or adrenaline, which suggests that high [K+]o influences twitch force and maximal rate by different mechanisms. In vivo levels of lactic acid, [K+]o, adrenaline, and heart rate previously observed during forced activity in Bufo did not significantly affect the contractile properties of heart muscle strips in vitro. Thus, although [K+]o significantly decreased twitch force, this detrimental effect was more than counteracted by the positive inotropic effect of lactic acid and adrenaline.     

四川江油附子生物碱和新的强心成分研究

从四川江油附子(Aconitum carmichaeli Debx.)的生附片中分离出海帕乌头碱(hypeconitine)、乌头碱(aconitine)、美沙乌头碱(mesaconitine)、尼奥灵(neoline)、卡拉可林(karakoline)、北乌碱(beiwutine)、附子灵(fuziline)、江油乌头碱(jiangyouaconitine)、去氧乌头碱(deoxyaconitine)、附子亭(fuzitine)、新江油乌头碱(neojiangyouaconitine)、宋果灵盐酸盐(songoring.HCl)和尿嘧啶(uracil)。其中新江油乌头碱和附子亭为新化合物;去氧乌头碱、北乌碱、宋果灵盐酸盐和尿嘧啶为本植物中首次发现。尿嘧啶对蟾蜍离体心脏具有明显的加强心肌收缩作用,作用随剂量增加与时间延长而逐渐增强,且不影响心率,认为是一种新型的强心成分,为首次发现。本文对附子的强心、止痛及抗炎的活性及其开发新药加以讨论。     

Contractile parameters and occurrence of alternans in isolated rat myocardium at supra-physiological stimulation frequency

The cardiac refractory period prevents the heart from tetanic activation that is typically used in noncardiac striated muscle tissue. To what extent the refractory period prevents successive action potentials to activate the excitation-contraction coupling process and contractile machinery at supra-physiological rates, such as those present during ventricular fibrillation, is unknown. Using multicellular trabeculae isolated from rat hearts, we studied amplitude and kinetics of contraction at rates well above the normal in vivo rat heart range. We show that even at twice the maximal heart rate of the rat, little or no mechanical instability is observed; twitch contractions are at steady state, albeit with an elevated active diastolic force. Although the amplitude of contraction increased within in vivo heart rates (positive force-frequency response), at frequencies beyond the maximal heart rate (10-30 Hz) a steady decline of contractile amplitude is observed. Not until 30 Hz do the majority of the isolated muscle preparations show mechanical alternans, where strong and weak beats alternate. Interestingly, unlike striated limb skeletal muscle, fusing of twitch contractions did not cause a continuous increase in peak force: at frequencies of 10 Hz and above, systolic force declines with relatively little elevation in diastolic force. Contractile kinetics continued to accelerate, from 1 Hz up to 30 Hz, whereas the relative speed of contraction and relaxation remained closely coupled, reflected by a singular linear relationship between the maximal and minimal derivative of force (dF/dt). We conclude that cardiac muscle can produce mechanically stable steady-state contractions at supra-physiological pacing rates, while these contractions continue to decline in amplitude and increase in diastolic force past maximal heart rate.     

Study of Cardiotonic Effect of Venom of the Green Toad Bufo viridis

In experiments on the isolated heart of frogs, cats, and rats, cardiotonic effect of the green toad Bufo viridis Laur. venom was studied. It has been shown that both the venom and the fraction of bufodienolides isolated from it produce an increase of the strength of cardiac contractions and, to a lesser extent, of the heart rate in cold-blooded and warm-blooded animals. A high selectivity of the venom inotropic effect was seen as an increase of the rate characteristics of elevation or reduction of the pressure in the rat heart left ventricle. The venom and bufadienolides increase the frog atrial trabecula contraction without a rise of the slow incoming (calcium) current. A similarity of mechanisms of cardiotonic effects of the venom and of the plant cardiac glycosides is discussed.     

Effect of insulin on the myocardium of the active, hibernating and wakening ground squirrel Citellus undulatus

The effect of insulin (0.1-100 nM) on isometric force of contraction in isolated ground squirrel papillary muscle was investigated. In summer, autumn and winter active animals, insulin had a negative inotropic effect on papillary muscles, decreasing the amplitude of contraction by about 30% of the control value. In some cases, predominantly in the summer group of animals, insulin produced different effects on contractility: low doses (0.1-0.5 nM) caused a transient activation of isometric contraction by about 10-15% of control, whereas high doses produced a negative inotropic effect by about 30% of the control level. During deep hibernation (at 5-6 degrees C of heart temperature) and during arousal from hibernation (from 3 to 20 degrees C), insulin had no significant effect on contractility. Opposite inotropic effects of insulin at concentrations of 0.1-50 nM were found during arousal: from 26 to 31 degrees C of heart temperature--a positive inotropic effect by about 20-25% of control, and from 32 to 36 degrees C--a negative one by about 30-40% of the control value.     

Combined effects of octopamine and filling pressure on the isolated heart of the lobster,Panulirus japonicus

Summary The effects of octopamine (OA) on the isolated and pumping heart of Panulirus japonicus were investigated. Under low filling pressure, OA (10^-7-10^-5 M) decreased the heart rate and enhanced the first systolic contraction (FSC) while reducing the second systolic contraction (SSC). The decrease in heart rate was transient whereas the enhancement of the FSC continued for 10 min or more after washout of OA. Pressure and OA synergistically intensified the FSC and reduced the SSC. The effect of OA on heart rate changed from a deceleration to an acceleration as the pressure was raised. Octopamine decreased both the firing frequency and the burst rate of the small cardiac neurons in a dose-dependent manner. In contrast, the amine often induced a slow ramp potential in the large cardiac neurons and increased their burst rate. Octopamine had no effect on the excitatory junction potentials evoked in cardiac muscle cells. Contraction and closure of the posterior cardioarterial valve were induced by OA, resulting in rebound internal heart pressure and stretching of the heart. The stretch augmented the heart rate and the FSC. The inhibition of small cardiac neurons by OA was related to the reduction of the heart rate and the SSC. The activation of large cardiac neurons and of cardiac and valve muscles by OA augmented the heart rate and the FSC. These multiple actions on the perfused heart lead to abolition of the SSC. After abolition of the SSC, increases of pressure can rapidly raise the heart rate.Abbreviations EJP excitatory junction potential - FLP first large potential - FSC first systolic contraction - OA octopamine - SLP second large potential - SSC second systolic contraction     

Relaxin increases rat heart rate by a direct action on the cardiac atrium.

Relaxin (Rlx) is best understood as a protein hormone of pregnancy that can influence pelvic and cervical connective tissue as well as uterine smooth muscle activity. Thus, it was unexpected that dense Rlx binding sites would be found in the rat cardiac atrium. To functionally characterize this finding, isolated rat atria were challenged with Rlx (0.3 to 30 ng/ml), and they responded with an increased rate (+36%) and force (+38%) of contraction Further studies in conscious normotensive and spontaneously hypertensive rats established by minipump circulating Rlx levels of about 0.5 and 5 ng/ml over 1 to 2 wks. There were significant increases in heart rate of 10-15%, with no consistent changes in blood or urine volume, water or food intake, and mean arterial pressure. We conclude that Rlx can directly stimulate rat cardiac atrial activity in vitro and cause chronotropy in vivo.     

Rheology of myocardium. The relation between force, velocity, sarcomere length and activation in rat cardiac muscle

The relations between force, shortening velocity and sarcomere length (F-V-SL) during cardiac contraction, underlie Starling's Law of the Heart. F-V-SL were investigated in isolated, intact and skinned trabeculae and myocytes from rat heart. SL and V were measured with laser diffraction techniques; F was measured with a silicon strain gauge. The "ascending" F-SL relation appeared to result from both length dependent sensitivity of the contractile system to activator calcium ions and the presence of restoring forces (Fr), residing in the collagen skeleton of the muscle. Fr increased exponentially with decreasing SL below slack length to 25% of maximal twitch force (Ft) at SL = 1.60 microns. V was inversely proportional to the load and attained a maximum at zero load (Vo). Vo increased with factors that increased F: [Ca++], SL, and time during the twitch. Vo reached a maximum and remained constant (13.5 microns/s) when F attained or exceeded 50% of its maximum value. Viscous force in the passive muscle increased with V to a maximum of 4% of Ft at V = 40 microns/s. The relation between Vo and these factors could be predicted by a model of contraction in which the measured visco-elastic properties of myocardium were incorporated, while the truly unloaded maximal velocity of sarcomere shortening was assumed to be independent of the level of activation of the contractile filaments. A model of the cardiac cycle which explains the relation between Frank's and Starling's laws is presented.     

The effects of Zn2+ on guinea pig isolated heart preparations

Isolated guinea pig hearts were perfused, by the Langendorff technique, with 30, 15, 7.5, and 1.5 μM Zn²⁺ in Chenoweth solution. Contractile force, coronary flow, and heart rate were recorded by means of Narco IV Physiograph. Calcium inhibitor (Verapamil 1 μM) and anion inhibitor (DIDS: 0.1, 1, and 5 μM) were used subsequently in the perfusing solutions in order to distinguish some of the possible mechanisms that Zn²⁺ uses to exert its action on cardiac myocytes. Isomolar to zinc concentration of Pb (II) and Co (II) were used to elucidate whether zinc effects on heart are specific for this metal. All hearts were used to estimate their zinc and calcium content by means of AAS (Atomic Absorption Spectrometry). Our findings suggest that the higher the Zn²⁺ concentration, the more toxic effects on heart are expressed by rapid reversible contractile force reduction and reversible specific changes of heart rate and flow. Zinc 1.5 μM in the perfusing solution benefits heart performance, but not significantly. Furthermore, the metal exerts specific effects on guinea pig heart, and it is rather possible that these effects on cardiac myocytes are held through cell membrane receptors.     

Residual force enhancement following eccentric induced muscle damage

During lengthening of an activated skeletal muscle, the force maintained following the stretch is greater than the isometric force at the same muscle length. This is termed residual force enhancement (RFE), but it is unknown how muscle damage following repeated eccentric contractions affects RFE. Using the dorsiflexors, we hypothesised muscle damage will impair the force generating sarcomeric structures leading to a reduction in RFE. Following reference maximal voluntary isometric contractions (MVC) in 8 young men (26.5±2.8y) a stretch was performed at 30°/s over a 30° ankle excursion ending at the same muscle length as the reference MVCs (30° plantar flexion). Surface electromyography (EMG) of the tibialis anterior and soleus muscles was recorded during all tasks. The damage protocol involved 4 sets of 25 isokinetic (30°/s) lengthening contractions. The same measures were collected at baseline and immediately post lengthening contractions, and for up to 10min recovery. Following the lengthening contraction task, there was a 30.3±6.4% decrease in eccentric torque (P<0.05) and 36.2±9.7% decrease in MVC (P<0.05) compared to baseline. Voluntary activation using twitch interpolation and RMS EMG amplitude of the tibialis anterior remained near maximal without increased coactivation for MVC. Contrary to our hypothesis, RFE increased (～100-250%) following muscle damage (P<0.05). It appears stretch provided a mechanical strategy for enhanced muscle function compared to isometric actions succeeding damage. Thus, active force of cross-bridges is decreased because of impaired excitation-contraction coupling but force generated during stretch remains intact because force contribution from stretched sarcomeric structures is less impaired.