The influence of cyclic concentric and eccentric submaximal muscle loading on cell viability in the rabbit knee joint

Background

Cartilage loading is associated with the onset and progression of osteoarthritis and cell death may play an important role in these processes. Although much is known about cell death in joint impact loading, there is no information on joints loaded by muscular contractions. The aim of this study was to evaluate the influence of muscle generated eccentric and concentric submaximal joint loading on chondrocyte viability. We hypothesised that eccentric muscle activation leads to increased cell death rates compared to concentric loading and to controls.

Methods

16 rabbits received either 50 min of uni-lateral, cyclic eccentric (n = 8) or concentric (n = 8) knee loading. Muscle activation for these dynamic conditions was equivalent to an activation level that produced 20% of maximum isometric force. Contralateral joints served as unloaded controls. Cell viability was assessed using confocal microscopy.

Findings

Eccentric contractions produced greater knee loading than concentric contractions. Sub-maximal contractions caused a significant increase in cell death in the loaded knees compared to the unloaded controls, and eccentric loading caused significantly more cell death than concentric loading.

Interpretation

Cyclic sub-maximal muscle loading of the knee caused increased chondrocyte death in rabbits. These findings suggest that low levels of joint loading for prolonged periods, as occurs in endurance exercise or physical labour, may cause chondrocyte death, thereby predisposing joints to degeneration.     

Tibiofemoral joint forces during maximal isokinetic eccentric and concentric efforts of the knee flexors

OBJECTIVE: The examination of muscular and tibiofemoral joint forces during maximal efforts of the knee flexors. DESIGN: The muscular and tibiofemoral joint knee forces during eccentric and concentric isokinetic efforts of the knee flexors were determined using a two-dimensional mathematical model. BACKGROUND: The examination of joint and muscle loading during isokinetic movements is important for the determination of safety of this exercise. METHODS: Ten healthy males performed three maximal isokinetic concentric and eccentric efforts of the knee flexors at angular velocities of 30 degrees s(-1), 90 degrees s(-1), 120 degrees s(-1) and 150 degrees s(-1). The muscular, tibiofemoral shear and compressive joint forces were determined using a two-dimensional model. RESULTS: The maximum muscular force ranged from 3.44 (Standard deviation, 1.32) times body weight to 6.19 (1.78) times body weight. The tibiofemoral compressive force ranged from 2.62 (1.17) times body weight to 5.89 (1.99) times body weight occurring at angles ranging from 0 degrees to 40 degrees of knee flexion. The posterior shear force ranged from 2.61 (1.33) times body weight to 3.89 (1.62) times body weight and was observed at angles ranging from 50 degrees to 80 degrees of knee flexion. Two-way analysis of variance designs indicated significant effects of type of muscle action and angular velocity on muscle and compressive forces (P<0.05). In contrast, the shear force was not affected by the type of muscle action or the angular velocity (P>0.05). CONCLUSIONS: Isokinetic efforts of the knee flexors induce high tibiofemoral joint forces, especially during high-speed eccentric tests.     

膝关节骨关节炎患者等长、等速向心和等速离心测试的比较观察

目的 评价膝关节骨关节炎（OA）患者患侧及健侧膝伸肌和屈肌在等长、等速向心和等速离心收缩时的功能特性及相互间的关系。方法 应用Biodex System 3型等速测试系统对54例单侧膝OA患者进行患侧和健侧膝伸肌和屈肌的等长、等速向心及等速离心肌力测试。结果 膝OA患者患侧膝关节伸肌和屈肌在不同收缩模式下的肌力均较健侧显著下降（P＜0．05），特别是在低速向心和低速离心收缩状态时的降低幅度尤为显著；同时患者的膝关节屈／伸肌肌力（H／Q）比值和动态控制率均提示其患侧肢体存在肌力平衡异常。结论 在对膝OA患者肌肉功能进行评定时，应选用等速肌力测试并同时分析其H／Q比值及动态控制率，只有这样才能对患者的肌肉状况作出全面而客观的评定。     

髌腱末端病运动员膝关节等速向心和离心运动时股四头肌表面肌电的变化

背景:髌腱末端病是腱止点部位的微细损伤,股四头肌群中的股内侧肌与股外侧肌之间的力量平衡发生变化,可直接导致髌骨产生异常运动从而对腱止点部位产生影响.目的:比较与分析髌腱末端病运动员膝关节力学特征和股四头肌表面肌电图的变化规律,为髌腱末端病的预防与治疗提供参考依据.设计、时间及地点:病例一对照观察,于2009-06/07在苏州大学体育学院运动机能评定实验室完成.对象:选择忠有髌腱末端病的男性运动员10人为髌腱末端病组,年龄(21.44±1.51)岁.配对选择10名无膝关节伤病的运动员作为正常对照组,年龄(21.37±1.36)岁.方法:对两组受试者分别进行膝关节力量和表面肌电测试,比较与分析膝关节屈肌力矩、伸肌力矩和股四头肌表面肌电的变化.主要观察指标:①等速运动时两组对象屈伸肌力矩的比较.②两组对象股四头肌表面肌电积分值的比较.③两组对象股内侧肉和股外侧肌表面肌电积分值比率的比较.结果:向心运动和离心运动时,末端病组屈伸肌峰力矩比值显著高于对照组(P＜0.05或P＜0.01),股内侧肌表面肌电积分值显著低于对照组(P＜0.05或P＜0.01),两组股外侧肌和股直肌表面肌电积分值差异均无显著性意义.向心运动和离心运动时,末端病组股内侧肌,股外侧肌比值均明显低于对照组(P＜0.05或P＜0.01).结论:髌腱末端病运动员膝关节屈肌与伸肌的力量差距较为突出,存在股内侧肌活动低下和股内侧肌与股外侧肌之间不平衡的现象.     

等速向心和离心肌力训练治疗膝关节骨性关节炎患者的有效性研究

目的：比较等速向心和等速离心肌力训练治疗膝关节骨性关节炎（OA）患者的有效性。方法：45例膝OA患者随机分为向心训练组、离心训练组和对照组。向心训练组患者（n=15）接受等速向心肌力训练．离心训练组（n=15）患者接受等速离心肌力训练，每周训练3次，共训练8周。用Biodex等速肌力测试训练系统评价膝OA患者训练前后的膝关节伸肌和屈肌的峰力矩改变。用目测类比评分法和Lequesne指数评价膝OA患者疼痛和功能障碍的改变。结果：两个训练组的膝OA患者的疼痛、功能障碍和肌肉峰力矩在训练后都有明显改善（P〈0．05）。而对照组8周后无明显改变。虽然不同的等速训练方法显示了一定的训练效果特异性．但在两个训练组之间各项参数无显著性差异。结论：等速向心和等速离心肌力训练方案在膝OA的治疗中都是有效的。在等速向心和等速离心训练之间未观察到显著性差异。     

Effect on maximal strength of submaximal exercise in Duchenne muscular dystrophy.

Four Duchenne muscular dystrophy patients, with quadriceps of at least antigravity strength, exercised one quadriceps submaximally 4 or 5 days per week for six months. The exercise was done under supervision and consisted of extending one knee from 90 degrees to full extension using the Cybex isokinetic exerciser. The other side was not exercised at all. The two sides were tested for maximal isokinetic strength monthly for twelve months and at 18 and 24 months after the beginning of the study. On the average, the exercised leg had a greater maximal torque both during and after the exercise period until the torques on both sides decreased to zero. The results indicate that submaximal exercise has no negative effect and may be of limited value in increasing strength in Duchenne muscular dystrophy.     

Reliability of concentric and eccentric torque during isokinetic knee extension in post-stroke hemiparesis

BACKGROUND: Emerging evidence on the velocity-dependent nature of force impairment in post-stroke hemiparesis has emphasized the complexity of strength and motor performance assessments in this clinical population. The need to establish reliability and responsiveness of muscle performance measures across a broad range of concentric and eccentric movement speeds is therefore clear, as these metrics will provide benchmarks both for making clinical inference and evaluating meaningful clinical change following interventions. METHODS: Isokinetic knee extensor strength was tested at 14 angular velocities in 17 adults with chronic post-stroke hemiparesis (>18 months), and 13 non-disabled controls. Identical tests were conducted on two occasions separated by two days. Test-retest reliability of maximal isokinetic torque was evaluated using intraclass correlation. Absolute reliability was assessed using standard error of measurement from which smallest real differences were derived. FINDINGS: Overall, intraclass correlation coefficients were excellent for both hemiparetic (0.891) and control (0.937) groups. Intraclass correlation coefficients for each criterion speed were also high for both groups (>0.86). Measurement error relative to the mean torque varied between 14.1% and 26.3% for hemiparetic subjects and 6.0-18.1% for controls. The smallest real difference relative to mean torque was 39.0-72.7% and 16.6-50.2% for hemiparetic and control subjects, respectively. INTERPRETATION: Isokinetic knee extension torque can be measured reliably in persons with chronic post-stroke hemiparesis and in non-disabled controls across a full functional range of concentric and eccentric speeds. Established measurement error and smallest real differences will aid interpretation of longitudinal observations of muscle performance in this clinical population.     

Effect of stabilization on maximal isokinetic torque of the quadriceps femoris muscle during concentric and eccentric contractions

The purpose of this study was to investigate the effect of stabilization on the maximal isokinetic torque generated by the quadriceps femoris muscle during concentric and eccentric contractions at different velocities using the KIN/COM isokinetic dynamometer. Fifteen female volunteers between the ages of 18 and 32 years were trained to perform maximal isokinetic concentric and eccentric contractions. Each subject participated in two testing sessions. In one testing session, subjects were stabilized maximally, and in the other testing session, subjects were stabilized minimally. Subjects were tested both concentrically and eccentrically at velocities of 30 degrees, 60 degrees, 90 degrees, 120 degrees, 150 degrees, 180 degrees, and 200 degrees/sec. The velocity sequence and stabilization procedure used were randomly assigned. Two nested model analyses of variance followed by post hoc comparisons were used to analyze the data. Results revealed no significant difference between the maximal stabilization procedure and the minimal stabilization procedure for concentric and eccentric contractions. The results of this study should aid rehabilitation specialists in the development of testing and rehabilitation procedures when using the KIN/COM.     

The effect of interval training combined with thigh cuffs pressure on maximal and submaximal exercise performance

The purpose of the study was to investigate the effect of interval training combined with a thigh cuffs pressure of +90 mmHg on maximal and submaximal cycling performance. Twenty untrained individuals were assigned either to a control (CON) or to an experimental (CUFF) training group. Both groups trained 3 days per week for 6 weeks at the same relative intensity; each training session consisted of 2-min work bout at 90% of VO(2max): 2-min active recovery bout at 50% of VO(2max). An incremental exercise test to exhaustion, a 6-min constant-power test at 80% of VO(2max) (Sub(80)) and a maximal constant-power test to exhaustion (TF(150)) were performed pre- and post-training. Despite the unchanged VO(2max), both groups significantly increased peak power output (CON: ～12%, CUFF: ～20%) that was accompanied by higher deoxygenation (ΔStO(2)) measured with near-infrared muscle spectroscopy. These changes were more pronounced in the CUFF group. Moreover, both groups reduced VO(2) during the Sub(80) test without concomitant changes in ΔStO(2). TF(150) was enhanced in both groups. Thus, an interval exercise training protocol under moderate restricted blood flow conditions does not provide any additive effect on maximal and submaximal cycling performance. However, it seems to induce peripheral muscular adaptations, despite the lower absolute training intensity.     

膝骨关节炎模型兔关节液中细胞因子白细胞介素1水平及复方归芪液的干预效应

目的:实验表明,白细胞介素1是关节软骨破坏中最重要的细胞因子.实验拟进一步观察兔膝骨性关节炎模型关节液中白细胞介素水平的变化以及复方归芪注射液的干预作用.方法:实验于2007-04/09在大连市第二人民医院骨科实验室完成.①实验分组:健康清洁级新西兰大白兔25只,6个月龄,体质量2.14～3.20kg,随机抽签法分为正常组、模型组、生理盐水组、透明质酸组和中药治疗组.每组5只.②实验方法:采用兔膝关节腔内注入木瓜蛋白酶造成骨关节炎的病理模型,正常组、模型组正常饲养,其他3组均于术后第8天给药(右下肢关节腔注射),以后每周2次,共10次.生理盐水组:每次注射9kg/L生理盐水0.15mL;透明质酸组:生理盐水稀释成浓度2kg/L,每次注入0.15mL:中药治疗组:每次注入生理盐水稀释液1kg/L和复方归芪注射液0.15mL.③实验评估:于造模后取材,采用双抗体夹心酶联免疫吸附实验法分别测定各组兔膝关节液中白细胞介素水平.结果:纳入大白兔25只,均进入结果分析.正常组未检出白细胞介素1,模型组、透明质酸组、中药治疗组白细胞介素1均呈高表达,但模型组与正常组比较差异显著(P＜0.01).透明质酸组、中药治疗组与模型组比较,白细胞介素1水平均降低(P＜0.01),而透明质酸组的作用优于中药治疗组(P＜0.05).结论:白细胞介素1在骨性关节炎发病过程及复方归芪注射液治疗中起重要作用.     

等速离心训练对膝关节骨关节炎患者的影响

目的探讨等速离心肌力训练对膝关节骨关节炎患者的康复疗效。方法运用Cybex-6000型等速肌力测试及训练系统对40例膝关节骨关节炎患者(共70个患膝)进行为期4周、每周3次的等速离心肌力训练。分别于训练前、后测定患者在60°/s、120°/s及180°/s等速运动时的峰力矩、单次最大作功量、平均功率及力矩加速能量;并将训练前、后患膝疼痛程度及下肢功能评分进行比较。结果患者经训练后,其患膝屈、伸肌群各项功能参数均有显著改善,并以屈膝肌各项功能参数的改善尤为显著;患膝疼痛及功能性行为能力评分亦均较治疗前有显著改善。结论等速离心训练能有效改善膝关节骨关节炎患者屈、伸肌群的各项功能参数(其中以屈膝肌的改善尤为显著);同时还能缓解患者疼痛,显著提高其功能性行为能力。     

Long-term repetitive mechanical loading of the knee joint by in vivo muscle stimulation accelerates cartilage degeneration and increases chondrocyte death in a rabbit model

BackgroundExcessive chronic loading is thought to be one factor responsible for the onset of osteoarthritis. For example, studies using treadmill running have shown an increased risk for osteoarthritis, thereby suggesting that muscle-induced joint loading may play a role in osteoarthritis onset and progression. However, in these studies, muscle-induced loading was not carefully quantified. Here, we present a model of controlled muscular loading which allows for the accurate quantification of joint loading. The aim of this study was to evaluate the effects of long-term, cyclic, isometric and dynamic, muscle-induced joint loading of physiologic magnitude but excessive intensity on cartilage integrity and cell viability in the rabbit knee.Methods24 rabbits were divided into an (i) eccentric, (ii) concentric, or (iii) isometric knee extensor contraction group (50 min of cyclic, submaximal stimulation 3 times/week for four weeks = 19,500 cycles) controlled by the stimulation of a femoral nerve cuff electrode on the right hind limb. The contralateral knee was used as a non-loaded control. The knee articular cartilages were analysed by confocal microscopy for chondrocyte death, and histologically for Mankin Score, cartilage thickness and cell density.FindingsAll loaded knees had significantly increased cell death rates and Mankin Scores compared to the non-loaded joints. Cartilage thicknesses did not systematically differ between loaded and control joints.InterpretationChondrocyte death and Mankin Scores were significantly increased in the loaded joints, thereby linking muscular exercise of physiologic magnitude but excessive intensity to cartilage degeneration and cell death in the rabbit knee.     

Association of MIF in serum and synovial fluid with severity of knee osteoarthritis

ObjectiveRecent evidences suggest that inflammation contributes to the development and progression of osteoarthritis (OA). This study aims to determine macrophage migration inhibitory factor (MIF) levels in serum and synovial fluid (SF) of patients with knee OA and to analyze the association of MIF levels with the radiographic severity of OA.Design and methods224 patients with knee OA and 186 healthy controls were enrolled in this study.ResultsHigher levels of serum MIF were found in knee OA patients compared with healthy controls. Knee OA patients with Kellgren and Lawrence (KL) grade 4 showed significantly elevated MIF levels in serum and SF compared with those with KL grade 2 and 3. MIF levels in serum and SF of knee OA patients were significantly related to disease severity evaluated by KL grading criteria.ConclusionMIF levels in serum and SF were closely related to the radiographic severity of OA.     

Correlation of plasma and synovial fluid osteopontin with disease severity in knee osteoarthritis

Objectives

The purposes of this study were to examine osteopontin levels in both plasma and synovial fluid of patients with primary knee osteoarthritis (OA) and to investigate their relationship with severity of the disease.

Design and methods

Thirty-two patients aged 53-83 years with knee OA and 15 healthy controls were enrolled in this study. Anteroposterior knee radiographs were taken to determine the disease severity of the affected knee. The radiographic grading of OA in the knee was performed by using the Kellgren-Lawrence criteria. Osteopontin levels in the plasma and synovial fluid were measured using enzyme-linked immunosorbent assay.

Results

The mean plasma osteopontin concentration of the knee OA patients was significantly higher compared with that of healthy controls (168.8 ± 15.6 vs 67.2 ± 7.7 ng/mL, P < 0.0001). Osteopontin levels in synovial fluid were significantly higher with respect to paired plasma samples (272.1 ± 15.0 vs 168.8 ± 15.6 ng/mL, P < 0.001). In addition, plasma osteopontin levels showed a positive correlation with synovial fluid osteopontin levels (r = 0.373, P = 0.035). Subsequent analysis showed that plasma osteopontin levels significantly correlated with severity of disease (r = 0.592, P < 0.001). Furthermore, the synovial fluid levels of osteopontin also correlated with disease severity (r = 0.451, P = 0.01).

Conclusion

The data suggest that osteopontin in plasma and synovial fluid is related to progressive joint damage in knee OA. Osteopontin may serve as a biochemical marker for determining disease severity and could be predictive of prognosis with respect to the progression of knee OA.