Isokinetic Training Effect of Ankle Positions on Knee Extensor Strength

[Purpose] The purpose of this study was to determine which ankle position most influences knee extensor strength in training programs for strengthening the knee extensors using three different active ankle positions. [Subjects] Twenty-one healthy adults (6 males and 15 females) participated in this study. [Methods] Subjects were trained isokinetically in knee extension and flexion at 70 or 80% of 1RM under three actively and naturally fixed, contracted ankle conditions: dorsiflexion, plantarflexion, and resting position. After each group successfully executed the training four times a week for three weeks, mean peak torque (PT) and total work (TW) variables were measured and compared at 60°/sec and 180°/sec among the three groups. [Results] Significant differences were revealed in knee extensor TW at 60°/sec, PT and TW at 180°/sec, with the greatest PT and TW observed with the ankle in active dorsiflexion position. [Conclusion] These results suggest that active ankle dorsiflexion in a knee strength training program may be more effective at increasing knee extensor strength than a resting or plantarflexion position.Key words: Ankle position, Knee extensor strength, Isokinetic training     

Efficacy of isokinetic exercise on joint position sense and muscle strength in patellofemoral pain syndrome

OBJECTIVE: The objective of this study was to demonstrate the impairment of knee joint position sense in individuals with patellofemoral pain syndrome and investigate the effects of isokinetic exercise on knee joint position sense and muscle strength. DESIGN: A total of 24 male patients complaining of anterior knee pain caused by overexertion and 24 male healthy individuals without symptoms were included for this investigation. Isokinetic exercise protocol was carried out at angular velocities of 60 degrees/sec and 180 degrees/sec. These sessions were repeated three times per week and lasted for 6 wks. At the beginning and after 6 wks of knee passive joint position sense, quadriceps and hamstring muscle strength and pain assessments were performed. RESULTS: After the isokinetic exercise, flexion peak torque (P < 0.05), extension peak torque (P < 0.01), flexion total work (P < 0.001), extension total work (P < 0.001), passive reproduction of knee joint position sense for 40 degrees of flexion (P < 0.05) and 50 degrees of extension (P < 0.01), and pain score (P < 0.001) improved significantly in the patellofemoral pain syndrome group. CONCLUSION: Isokinetic exercises have positive effects on passive position sense of knee joints, increasing the muscular strength and work capacity. These findings show that using the present isokinetic exercise in rehabilitation protocols of patients with patellofemoral pain syndrome not only improves the knee joint stabilization but also the proprioceptive acuity.     

Using isokinetic dynamometry to test ambulatory patients with multiple sclerosis

This study was designed to 1) determine whether isokinetic dynamometry is appropriate and safe for ambulatory patients with multiple sclerosis and 2) describe the idiosyncrasies the patients with multiple sclerosis exhibited during testing. Ten patients with multiple sclerosis and 20 healthy subjects were matched for age, sex, and weight. The isokinetic peak torque and endurance measurements of knee extensor and knee flexor muscles were recorded at selected angular velocities ranging from 0 to 275 degrees/sec and extensor:flexor muscle strength ratios were calculated. Statistical analysis (t tests) revealed that both the extensor and flexor muscle peak torque values for patients with multiple sclerosis were significantly lower than those for healthy subjects at all angular velocities (p less than .005 to p less than .001), and yet were similar in shape and slope. Mean extensor:flexor ratios for healthy subjects and for patients with multiple sclerosis were not significantly different at 70, 190, and 230 degrees/sec. Individual chart recordings identified any contractile difficulties or increased contraction time. Isokinetic testing is judged to be a safe and reliable form of objective neuromuscular testing for ambulatory patients with multiple sclerosis.     

Isometric and isokinetic measurement of hamstring and quadriceps strength.

This study evaluates quadriceps strength at varying movement velocities in a group of healthy subjects. Specific objectives included (1) investigating the effect of angular velocity on peak torque (PT) (2) investigating the effect of angular velocity on joint angle at peak torque (JAPT) and (3) evaluating whether the use of a relatively new isokinetic testing device yields new insights to previously accepted relationships between angular velocity and PT or JAPT. Twenty healthy subjects were tested for isometric and isokinetic knee extension and flexion strength on a LIDO Active Isokinetic Rehabilitation System at velocities of 0 degrees, 60 degrees, 120 degrees, and 180 degrees/sec. Isometric PT (0 degrees/sec) was found to be highly correlated with isokinetic PT for both extensors and flexors at all velocities (r = .88-.93, p less than .01). PT declined significantly as angular velocity increased for both extension (p less than .01) and flexion (p less than .05). A relationship between isometric and isokinetic JAPT was significant for extension only at 60 degrees and 180 degrees/sec (r = .48-.52, p less than .05). These results indicate that knee isometric and isokinetic PT as measured on the LIDO Active system are highly related for both extension and flexion. PT declined as isokinetic angular velocity increased. Isometric and isokinetic JAPT are significantly related only for extension.     

髌骨软化症患者膝关节等速肌力测试

目的 分析髌骨软化症患者膝关节周围肌力特征,并比较其与健康人的差异。方法 2021年3月,采用等速肌力测试与训练系统,对70例单膝发病髌骨软化症患者(观察组)和35例健康人(对照组)进行膝关节不同角速度(60°/s和180°/s)的屈、伸等速肌力测试。结果 60°/s和180°/s时,观察组患侧屈、伸肌峰力矩、峰力矩体质量比、总功均显著低于对照组(U> 1097.0,P <0.001);观察组患侧60°/s屈、伸肌和180°/s时伸肌峰力矩、峰力矩体质量比、总功均低于观察组健侧(|Z|> 2.121, P <0.05)。60°/s和180°/s时,观察组患侧屈伸肌力比值均明显大于健侧和对照组(U> 1810.0,|Z|>3.691, P <0.01)。结论 髌骨软化症患者的患膝屈、伸肌肌爆发力和耐力均减弱,膝关节肌力存在失衡现象。     

Isokinetic torque levels for high school football players.

One hundred fifteen high school football players were screened isokinetically for the knee extensor and flexor torque generating capabilities and muscle imbalances. Each player was tested on a Cybex II at speeds of 30 degrees/sec and 180 degrees/sec. The subjects were stratified by age (15, 16, 17) and by position (linemen vs receivers and backs). Significant (p less than 0.05) torque differences were observed at both the slow and fast speeds for the knee extensors and flexors across the 3 age groups. However, the flexion to extension ratios did not differ significantly. On the other hand, when considering the positions, flexor torque and flexion to extension ratio at the slow speed were greater (p less than 0.05) for the linemen than the receivers and backs. Partial correlation analyses showed that body weight had the greatest effect on the knee torque values. It was concluded that basic torque measures differed with age and by position in the sport of football. Also, speed of movement altered the force generating capabilities of the muscle and resultant ratios.     

Determining the number of repetitions to establish isokinetic knee evaluation protocols specific to angular velocities of 60°/second and 180°/second

IntroductionThis study aims to develop a standard number of repetition at angular velocities of 60°/sec and 180°/sec and define the difference of number of repetitions between genders.MethodOne hundred ninety-six athletes (judo, volleyball, Greco-Roman wrestling, runners, and gymnastics) were involved. Concentric-concentric isokinetic muscle strength of the knee flexor-extensor muscles of the athletes were performed with an ISOMED 2000 isokinetic dynamometer. The evaluation test protocol consisted of 10 repetition of knee flexion-extension at 60°/sec and 30 repetitions at 180°/sec.ResultsAthletes performed with maximal knee flexion strength at their second and third trial at 60°/sec and third-forth trial at 180°/sec. It was found that 2 repetitions and 2–3 repetitions were needed for knee extension peak torque at 60°/sec and 180°/sec respectively. The difference between the genders was significant at 60°/sec for knee flexion and extension on the dominant side; at 180°/sec for knee extension on the dominant and non-dominant side. It was determined that 3 repetitions for 60°/sec, 4 repetitions for 180°/sec were enough to determine peak torque values.DiscussionOptimal number of repetitions is crucial so that athletes could have the opportunity to reach maximal strength without unnecessary workload or waste of time.ConclusionsProtocols involving 3 repetitions for 60°/sec, 4 repetitions for 180°/sec were enough to determine peak torque values. Gender of athletes should be considered when establishing isokinetic knee evaluation protocols.     

不同下肢体位振动对脑卒中患者下肢肌力及运动功能的影响

目的:探讨不同下肢体位振动治疗对脑卒中患者下肢功能和肌力的影响。方法:选择2018年7月至2019年8月于西南医科大学附属医院康复科收治的72例脑卒中患者,随机分为对照组、迈步振动组、后伸振动组、屈膝运动振动组,每组18例。三种振动治疗组在对照组基础上增加不同体位下的振动治疗,20min/次,1次/天,5天/周,持续6周。在基线、振动训练6周、随访12周时评估Fugl-Meyer量表下肢部分、起立-行走计时试验(TUG)、膝屈伸肌等速肌力峰力矩。结果:共66例患者完成该研究。各组6周及12周时Fugl-Meyer、TUG、双侧伸膝及屈膝肌峰力矩均较治疗前有显著性差异(P<0.05)。三种振动治疗组6周及12周时Fugl-Meyer、TUG、患侧伸膝肌峰力矩较对照组有显著性差异(P<0.05)。屈膝运动振动组6周时患侧伸膝肌峰力矩显著高于迈步组及后伸组(P<0.05)。四组健侧伸膝肌、双侧屈膝肌峰力矩在6周与12周差异不具备显著性意义(P>0.05)。结论:全身振动疗法能提高脑卒中患者患侧膝关节伸肌肌力与下肢整体运动功能,且屈膝运动振动治疗在提高患侧伸肌力量方面更具优势。     

Effect of resisted knee flexion on knee extension torque

We tested the principle of "reversal of antagonists" by measuring the effect of resisted knee flexion on subsequent peak knee extension torque at velocities of 60 degrees/sec and 120 degrees/sec using an isokinetic dynamometer. We determined peak knee extension torques from torque curves produced during knee extension that was performed reciprocally with either passive or maximum voluntary resisted knee flexion. We used a crossover design so that all 18 healthy adult subjects performed knee extension reciprocally with both passive and resisted knee flexion. Paired means t tests revealed no statistically significant difference between the peak knee extension torques produced under the two knee flexion conditions either at 60 degrees/sec or 120 degrees/sec. We, therefore, concluded that resisted knee flexion does not augment peak knee extension torque under our conditions of testing. The concept of reversal of antagonists was not supported. Antagonistic muscle functioning, therefore, may be irrelevant to agonist isokinetic testing and training in neurologically healthy persons.     

Comparison of isokinetic muscle strength and muscle power by types of warm-up

[Purpose] The purpose of this study was to clarify the influence of static stretching at warm-up on the isokinetic muscle torque (at 60°/sec) and muscle power (at 180°/sec) of the flexor muscle and extensor muscle of the knee joint. [Subjects and Methods] The subjects of this study were 10 healthy students with no medically specific findings. The warm-up group and warm-up with stretching group performed their respective warm-up prior to the isokinetic muscle torque evaluation of the knee joint. One-way ANOVA was performed by randomized block design for each variable. [Results] The results were as follows: First, the flexor peak torque and extensor peak torque of the knee joint tended to decrease at 60°/sec in the warm-up with stretching group compared with the control group and warm-up group, but without statistical significance. Second, extensor power at 180°/sec was also not statistically significant. However, it was found that flexor power increased significantly in the warm-up with stretching group at 180°/sec compared with the control group and warm-up group in which stretching was not performed. [Conclusion] Therefore, it is considered that in healthy adults, warm-up including two sets of stretching for 20 seconds per muscle group does not decrease muscle strength and muscle power.Key words: Stretching, Warm-up, Muscle power     

Test-retest reliability of isokinetic knee extension and flexion

OBJECTIVE: To assess reliability of isokinetic peak torque and work for knee flexion and extension. DESIGN: Single-group test-retest. SETTING: University laboratory. PARTICIPANTS: Eleven men and 7 women (mean age, 21 y). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURE: Peak torque and work for concentric and eccentric knee extension and flexion were recorded at 60 degrees/s for 3 trials on 2 occasions. Intraclass correlation coefficient model 3,1 (ICC(3,1)), standard error (SE) of measurements, and smallest real differences were calculated for the maximum and for the mean peak torque and work of the 3 repetitions. RESULTS: Relative reliability was "very high" for peak torque and work (ICC range, >.90). The SE measurements ranged between 5% and 10% of the initial values for both peak torque and work. The smallest change that indicates a real improvement for a single subject (smallest real differences) ranged from 12% to 25% for peak torque and work variables and from 25% to 30% for the peak torque ratios. CONCLUSIONS: Isokinetic concentric and eccentric knee extensor and flexor strength variables are reliable when measured by the same examiner in asymptomatic subjects.     

Effect of quadriceps femoris muscle stretch on knee extension torque

Peak and angle specific knee extension torques produced after a quadriceps femoris muscle stretch and after a 15-second rest were compared to determine the effect of stretch on knee extension torque. Twenty healthy subjects performed eight maximum voluntary knee extensions at 90 degrees/sec under each condition. Although peak torque and torques at 15, 30, 45, and 60 degrees from full extension were measured, knee extension torque was only significantly greater (p less than .02) at 60 degrees of knee flexion after quadriceps femoris muscle stretch. The absolute difference, which was only a mean 4.9 N X m (3.6 ft-lb), was not substantial. When quadriceps femoris muscle stretch is a consequence of passive knee flexion at 90 degrees/sec, knee extension torque is apparently facilitated only during the initial part of the knee extension movement. Therefore, in healthy patients, a muscle stretch, such as used in this study, is probably of little therapeutic value.     

Knee extensor torque and BMI differently relate to sit-to-stand strategies in obesity

BackgroundObesity alters whole body kinematics during activities of daily living such as sit-to-stand (STS), but the relative contributions of excess body mass and decreased relative strength are unknown.MethodsThree-dimensional motion analysis data was collected on 18 obese subjects performing sit-to-stand (chair height: 52 cm). Isometric knee extensor strength was measured at 90⁰ knee flexion. Forward stepwise linear regression was used to determine the association between the independent variables BMI and the knee extensor torque with the dependent variables: foot position and trunk kinematics.FindingsBMI, but not knee extensor torque, was inversely related to shank angle and positively related to stance width. Relative knee extensor torque, but not BMI, was inversely associated with initial trunk angle, peak trunk flexion angle, and peak trunk extension velocity (r² = 0.470–0.495). BMI was positively associated with peak trunk flexion velocity, but no other parameters of trunk kinematics. In the final regression model, BMI was the primary predictor (r² = 0.423) and relative knee extensor strength served as a secondary predictor (r² = 0.118) of peak trunk flexion velocity.InterpretationBMI and knee extensor strength differently contribute to sit-to-stand performance strategies in obese subjects. Muscle strength may be an important determinant of whole-body kinematics during activities of daily living such as STS.     

Skeletal muscle strength following orthotopic heart transplantation]

AIM OF THE STUDY: Strength measurement of thigh muscles of patients after orthotopic heart transplantation (HTX) with a sedentary lifestyle, entering a cardiac rehabilitation program. DESIGN: Cross-sectional study; values are compared to patients with chronic heart failure (CHF) and healthy controls. METHODS: Isometric and isokinetic peak torque of knee extensor and flexor muscles measured on a Cybex 6000. Twenty minutes' muscle fatigue test of knee extensor muscles. Test of motor tasks of daily living. RESULTS: HTX group: n = 18, age 59 +/- 7 years, body mass index (BMI) 29 +/- 5, months after HTX 46 +/- 36 months; CHI group: n = 24, age 55 +/- 8 years, BMI 25 +/- 4, months after CHF 19 +/- 16 months; control group: n = 10, age 55 +/- 6 years, BMI 26 +/- 5. The HTX group differed significantly (p < 0.05) from the CHI group. Peak torque of knee extensor muscles: HTX: 120.3 +/- 8.4; CHI: 127.8 +/- 8.0 Nm; controls: 158.3 +/- 5.5 (ANOVA p < 0.05); peak torque of knee flexor muscles: HTX 65.6 +/- 5.9 Nm; CHI 70.1 +/- 6.2 Nm; controls 84.4 +/- 3.1 Nm(ANOVA p < 0.01). Peak torque of knee extensor muscles related to body weight: HTX: 137.4 +/- 10.0 Nm%, CHI: 162.6 +/- 9.3 Nm%, control group 202.8 +/- 5.7 Nm% (ANOVA p < 0.01). Muscle fatigue test of knee extensor muscles: isometric maximal strength (maximal voluntary contraction, MCV; HTX vs. CHI): 331.6 +/- 14.7 N vs. 335.5 +/- 18.6 N (n.s.), MVC after 5 minutes 296.3 +/- 15.7 N vs. 288.4 +/- 16.7 N; MVC after 10 minutes: 283.5 +/- 15.7 N vs. 282.5 +/- 17.7 N; MVC after 15 minutes 275.7 +/- 13.7 N vs. 280.6 +/- 21.6 N. No significant differences between groups were observed. All values were significantly lower than those of healthy controls (406.2 N; 385.9 N; 373.7 N and 369.6 N). There was a significant decline in MVC after 5 minutes compared to initial values (p < 0.01), in both patients groups but not in the control group. No further decline in MVC was observed beyond the 5th minute of the fatigue test (p > 0.05). CONCLUSION: Peak torque related to body weight and muscle endurance of knee extensor muscles of sedentary patients after orthotopic HTX do not significantly differ from those of comparable patients with CHF but do differ from those of healthy controls. Specific training of muscle strength is needed for patients even several years after orthotopic heart transplantation.     

Quadriceps weakness in a family with nemaline myopathy: influence of knee angle

Nemaline myopathy is a congenital neuromuscular disorder, which primarily affects the thin filaments. Clinically the most important feature is muscle weakness; however, this weakness is poorly understood. The present investigation aimed to determine the torque angle relationship of the knee extensor muscles during in vivo muscle contractions in a family with a novel phenotype of nemaline myopathy. The results of this study show that quadriceps weakness occurs predominantly at higher knee flexion angles, but relatively normal strength was found at angles closer to full knee extension. When the relative torque angle relationships were considered, torque loss at smaller than optimum knee flexion angle was greater in the patients compared with the controls. In addition, the optimum angle for maximal quadriceps torque production was shifted towards smaller knee flexion angles in the patients. This suggests that a weakness specifically at higher knee flexion angles probably occurs as a result of adaptations consequently to the disease. Furthermore, it is important to assess muscle function at different joint positions to allow adequate interpretation of muscle weakness.     

Reduction of spastic hypertonia during repeated passive knee movements in stroke patients

OBJECTIVES: To quantify changes in spastic hypertonia during repeated passive isokinetic knee movements in stroke patients and to assess the role of muscle activity. DESIGN: A between-groups design with repeated measures. SETTING: Rehabilitation center for stroke patients. PARTICIPANTS: Ten stroke patients with hypertonia and 10 healthy subjects matched for age and gender. INTERVENTION: With an isokinetic apparatus, movements were imposed on the knee in series of 10 repetitions at speeds of 60 degrees /s, 180 degrees /s, and 300 degrees /s. MAIN OUTCOME MEASURES: Spastic hypertonia was assessed on the basis of torque measurement and electromyographic activity of the quadriceps, hamstrings, and gastrocnemius muscles. RESULTS: Compared with the controls, stroke patients presented a significantly stronger torque reduction during the mid- and endphases of movements at all speeds tested (P<.05). The strongest torque decline occurred during knee flexion and during the first movements. The effect increased toward the end phase of movements and with increasing speeds. The effect of movement repetitions on torque measurements was unchanged after electromyographic activity was included in the statistical analysis, except during extension movements at 180 degrees /s and 300 degrees /s. CONCLUSION: Passive movements of the knee induced a decrease of spastic hypertonia in stroke patients through a combination of reflexive and mechanical factors. The role of these mechanisms is velocity dependent and differs for flexion and extension movements.     

Knee extensor and flexor torque characteristics before and after unilateral total knee arthroplasty

OBJECTIVE: The purpose of this study was to document torque characteristics and strength recovery of the knee extensors and flexors before and up to 1 yr after unilateral total knee arthroplasty. Our goal was to also document the responsiveness of isokinetic testing over repeated measures. DESIGN: Thirteen individuals voluntarily participated in this study. Torque production of the knee extensors and flexors was assessed isokinetically at 1.047 and 3.142 radians/sec. RESULTS: Regardless of time, the knee extensors and flexors on the involved side generated a range of 76 and 82% of the average peak torque produced by the uninvolved side at both 1.047 and 3.142 radians/sec, respectively. At 30 days after surgery, there was a "dip" in both knee extensor and flexor torque production. Responsiveness indices for the knee extensors and flexors ranged from 0.95 to 2.12 at 1.047 radians/sec. At 3.142 radians/sec, the responsiveness indices for the knee extensors and flexors ranged from 0.65 to 2.87. CONCLUSION: One year after surgery, there continues to be knee extensor and flexor strength asymmetry between limbs. Moreover, within the first month after surgery, the knee extensors and flexors are at the weakest point compared with before, 60 days, and 1 yr after surgery. Isokinetic testing is a useful tool to document torque production before and in the early time after unilateral total knee arthroplasty.     

Tai Chi Chuan to improve muscular strength and endurance in elderly individuals: a pilot study

OBJECTIVE: To evaluate the training effect of a Tai Chi Chuan (TCC) program on knee extensor muscular strength and endurance in elderly individuals. DESIGN: Before-after trial. SETTING: Community setting. PARTICIPANTS: Forty-one community dwelling subjects aged 61.1 +/- 9.8 years undertook a TCC program. Nine dropped out during the study. Pretraining and posttraining measurements were obtained from 15 men and 17 women. INTERVENTION: Subjects participated in a 6-month TCC program. Each session consisted of 20 minutes of warm-up, 24 minutes of structured TCC training, and 10 minutes of cool-down exercises. MAIN OUTCOME MEASURES: Peak torque of dominant and nondominant knee extensors was tested at speeds of 60 degrees , 180 degrees , and 240 degrees/sec concentrically and eccentrically. Muscular endurance of the knee extensor was tested at the speed of 180 degrees /sec. RESULTS: In the group of men, concentric knee extensor peak torque increased by 15.1% to 20.0% and eccentric peak torque increased by 15.1% to 23.7%. The group of women also showed increases, ranging from 13.5% to 21.8% in concentric peak torque, and 18.3% to 23.8% in eccentric peak torque. In addition, the knee extensor endurance ratio increased by 9.6% to 18.8% in the men and 10.1% to 14.6% in the women. CONCLUSION: TCC training may enhance muscular strength and endurance of knee extensors in elderly individuals.     

前交叉韧带损伤并发或不并发髌股关节软骨损伤等速角度力矩曲线的差异

目的 探讨前交叉韧带损伤并发或不并发髌股关节软骨损伤患者的等速角度力矩曲线差异。方法 回顾分析2018年9月至2019年9月行膝关节镜探查术并在术前行等速肌力测试的患者,选取年龄、性别、半月板损伤相匹配的前交叉韧带损伤并发或不并发髌股关节软骨损伤患者各17例。术前采用等速肌力测试仪进行180°/s、60°/s的膝关节等速和等长屈伸测试。采用1°递增的平均力矩结果进行标准化(力矩/体质量),比较两组间角度力矩曲线差异。结果 180°/s下,两组间健侧和患侧屈膝力矩比较均无显著性差异(P > 0.05);两组间健侧伸膝力矩比较无显著性差异( P > 0.05),患侧伸膝力矩在88°~90°有显著性差异( t > 2.102, P < 0.05),余角度均无显著性差异( P > 0.05)。60°/s下,两组间健侧屈膝力矩在62°~82°有显著性差异(| t| >2.056, P < 0.05),余角度无显著性差异;两组间患侧屈膝力矩比较无显著性差异( P > 0.05);两组间健侧和患侧伸膝力矩比较均无显著性差异( P > 0.05),但无软骨损伤的伸膝力矩有高于髌股软骨损伤的趋势。在180°/s等速屈伸力矩曲线的起始阶段会出现一个曲线变化。髌股软骨损伤组患侧等长伸膝力矩明显小于无髌股软骨损伤组( t = 2.858, P < 0.01),两组间患侧等长屈膝及健侧屈、伸力矩比较无显著性差异( t < 1.905, P > 0.05)。 结论 前交叉韧带损伤并发髌股软骨损伤较不并发髌股软骨损伤患者的等速运动速度越低,力量差异越显著。并发髌股软骨损伤的前交叉韧带损伤患者训练力量时建议采用高速运动。