Obtaining reliable measurements of knee extensor torque produced during maximal voluntary contractions: an experimental investigation.

The purpose of this study was to develop and test a protocol that could be used to obtain reliable measurements of knee extensor torque produced during maximal voluntary contractions. On each of 3 days, 10 subjects performed six consecutive maximal voluntary contractions, in the same randomized order, for each of the following 10 conditions: concentric isokinetic contractions at velocities of 30 degrees, 90 degrees, 120 degrees, and 180 degrees/s; eccentric isokinetic contractions at velocities of 30 degrees, 90 degrees, 120 degrees, and 180 degrees/s; and isometric contractions at 40 and 60 degrees of knee flexion. The peak torques produced were examined to determine on which day and during which contraction subjects produced the greatest torques for each condition. This information was used to develop a practice protocol. Fifteen different subjects were tested following this protocol. Subjects participated in two practice sessions, a test session, and a retest session. Intraclass correlation coefficients (ICCs) were calculated to determine the degree of agreement between torques for the test and retest sessions. The ICCs ranged from .87 to .98. The protocol developed appears to be useful for obtaining reliable measurements of knee extensor torque.     

What change in isokinetic knee muscle strength can be detected in men and women with hemiparesis after stroke?

OBJECTIVE: To assess the intra-rater (between occasions) test-retest reliability of isokinetic knee muscle strength measurements in subjects with chronic poststroke hemiparesis and to define limits for the smallest change that indicates real (clinical) improvements for stroke patients. SUBJECTS: Fifty men and women (mean age 58 +/- 6.4 years) 6-46 months post stroke, able to walk at least 300 m with or without a unilateral assistive device. METHODS: Maximal concentric knee extension and flexion contractions at 60 degrees/s and 120 degrees/s, and maximal eccentric knee extension contractions at 60 degrees/s, with the paretic and nonparetic limbs, were performed seven days apart using a Biodex dynamometer. MEASURES: Reliability of the maximum peak torque measurements was evaluated with the intraclass correlation coefficient (ICC(2,1)), the Bland and Altman analyses, the standard error of measurement (SEM and SEM%) and the smallest real difference (SRD and SRD%). RESULTS: Test-retest agreements were high (ICC(2,1) 0.89-0.96) with no discernible systematic differences between limbs, angular velocities and modes. The SEM%, representing the smallest change that indicates a real (clinical) improvement for a group of subjects, was relatively small (8-20%). The SRD%, representing the smallest change that indicates a real improvement for a single subject ranged from 26% to 33% for concentric knee extension, from 39% to 55% for concentric knee flexion, and from 22% to 25% for eccentric knee extension. CONCLUSION: Isokinetic knee muscle strength can be reliably measured and used to detect real improvements following an intervention for single subjects as well as for groups of subjects with chronic mild to moderate hemiparesis after stroke.     

Concentric versus combined concentric-eccentric isokinetic training: effects on functional capacity and symptoms in patients with osteoarthrosis of the knee

OBJECTIVE: To compare the effects of concentric and coupled concentric-eccentric isokinetic resistance training on functional capacity and symptoms of patients with osteoarthrosis (OA) of both knees. DESIGN: Repeated measures. SETTING: A university exercise physiology laboratory. PARTICIPANTS: Twenty-three volunteers, ages 41 to 75 years. Patients were randomly assigned to 3 groups: concentric (CON, n = 9), concentric-eccentric (CON-ECC, n = 8), and nontreatment (NONTX, n = 6). INTERVENTIONS: The CON group performed 12 concentric contractions of each knee extensor and flexor muscles; the CON-ECC group performed 6 concentric and 6 eccentric contractions of each knee muscle group by using a spectrum of angular velocities ranging from 30 degrees/s to 180 degrees/s with 30 degrees/s intervals, for both sides, 3 days a week for 8 weeks. MAIN OUTCOME MEASURES: Functional capacity (rising from a chair, walking, stair climbing and descending) and pain during rest and activities, peak torque, and cross-sectional area (CSA) of knee muscle groups of subjects were tested before and after training. RESULTS: Both training groups showed marked decreases (P <.001) in pain scores and increases (P <.001) in functional capacity together with increases (P <.05--.01) in peak torque and CSA of knee muscles. However, the NONTX group did not display these marked changes after the 8-week period. The results also indicated that concentric-eccentric training has a greater influence on functional capacity, especially stair climbing and descending, than that of concentric training when compared with NONTX group; however, the improvements in pain measurements were better in the CON group compared with the CON-ECC group after the training. CONCLUSIONS: The results suggest that with the isokinetic resistance training used in this study, it is possible to improve functional capacity and decrease pain in patients with OA of the knee. The results also showed that extensive training involving a high number of repetitions and eccentric contractions was safe, effective, and well tolerated for the patients with knee OA.     

Continuous versus separate isokinetic test protocol: the effect of estradiol on the reproducibility of concentric and eccentric isokinetic measurements in knee muscles.

OBJECTIVE: To investigate the effects of estradiol on the reliability of concentric and eccentric isokinetic measurements of knee muscles and to compare the reproducibility of measurements in a continuous test protocol and a separate test protocol. DESIGN: Repeated measurements. SETTING: A university exercise physiology laboratory. PARTICIPANTS: Twenty healthy sedentary women volunteers, aged 19 to 37 years, who had regular menstrual cycles (ranging from 27 to 35 days). Subjects were randomly divided into two groups: continuous test group (n = 10) and separate test group (n = 10) and tested at the menstrual phase (days 1 to 3) and preovulatory phase (days 12 to 14) in both legs. METHODS: Continuous reciprocal flexion-extension contractions were used in the continuous test group, and separated flexion and extension contractions were used in the separate test group. Four different test protocols were designed to determine the effects of test mode and number of contractions on the isokinetic measurements: Group A, 4 reciprocal flexion-extension repetitions at each angular velocity of 60 degrees/sec and 180 degrees/sec in one leg in the continuous test group; Group B, 4 and 20 reciprocal flexion-extension repetitions at 60 degrees/sec and 180 degrees/sec, respectively, in the contralateral leg in the same group; Group C, 4 repetitions in extensors and flexors at each angular velocity of 60 degrees/sec and 180 degrees/sec with a 5-minute rest between the two muscle groups in one leg in the separate test group; and Group D, 4 repetitions at 60 degrees/sec and 20 repetitions at 180 degrees/sec for extensors and flexors with a 5-minute rest between the two muscle groups in the contralateral leg in the same group. Blood samples were analyzed for sex hormones, creatine kinase, and lactate dehydrogenase before the tests at the menstrual phase and the preovulatory phase. In addition subjective assessment of muscle soreness was made at each blood sampling. RESULTS: Concentric and eccentric peak torque, average power, total work, and endurance ratio at both angular velocities were not significantly different in the two phases of the cycle by paired observation t test for each of the four groups. Except for concentric and eccentric endurance ratios of quadriceps and hamstrings, and concentric peak torque and average power of hamstrings at 180 degrees/sec in Group D, intraclass correlation coefficients of tested variables showed correlations that were moderate to excellent (p < .05) between two phases. In addition, there were no significant correlations between estradiol and the tested variables. Resting serum creatine kinase and lactate dehydrogenase activities and the score of muscle soreness were at the baseline and not significantly different prior to the tests performed at preovulatory and menstrual phases. CONCLUSIONS: The results suggest that: (1) reproducibility of isokinetic tests during the menstrual cycle is not influenced by sex hormone fluctuations, particularly estradiol; (2) when compared with the separate test protocol used in this study, the continuous test protocol is more appropriate to measure peak torque, average power, total work, and endurance ratio for both muscle groups of the knee even if the number of contractions is changed. However, these conclusions are specific to sedentary individuals; to make more valid conclusions, further studies with different subject groups are needed.     

Reliability of knee extensor and flexor torques during continuous concentric-eccentric cycles

Peak and average torques of the knee extensors and flexors were determined on three occasions within ten days. On each occasion, 20 healthy women and 15 healthy men performed three continuous concentric-eccentric cycles with no pause between muscle actions or between cycles at 45 degrees and 90 degrees/sec angular velocities. Peak and average torques did not vary significantly or systematically over the three test occasions. Intraclass correlation coefficients (ICCs), based on one occasion, ranged from 0.79 to 0.91 for peak torques and from 0.75 to 0.88 for average torques. At 45 degrees/sec angular velocity, the ICCs for peak torque tended to be greater than those for average torque, whereas at 90 degrees/sec angular velocity the ICCs were similar whether calculated using peak or average torque. The ICCs during knee extension were greater than those during knee flexion. Eccentric muscle actions produced significantly higher torques than did concentric actions (p less than 0.01). A continuous concentric-eccentric cycle protocol which emphasizes teaching the subject to perform the test maneuvers and using at least three submaximal practice contractions and one maximal practice contraction can produce reliable isokinetic torques.     

Joint angle and contraction mode influence quadriceps motor neuron pool excitability

OBJECTIVE: The purpose of the study was to compare the central activation ratio (CAR) of eccentric contractions to isometric contractions at 30 and 70 degrees of knee flexion. DESIGN: A repeated-measures design was used. CARs were measured at 30 and 70 degrees of knee flexion in 16 healthy subjects during both eccentric and isometric modes of contraction. CARs were measured using the superimposed burst technique. RESULTS: Isometric CARs at 30 degrees (0.88+/-0.069) of knee flexion were significantly higher (P<0.001) than at 70 degrees (0.77+/-0.116). Eccentric CARs were significantly higher (P=0.013) at 70 degrees (0.87+/-0.085) of knee flexion compared with 30 degrees (0.8+/-0.09). At 30 degrees of knee flexion, isometric CARs were significantly higher (P=0.003) than eccentric CARs. At 70 degrees, eccentric CARs were higher (P<0.001) when compared with isometric CARs. CONCLUSIONS: Our results provide evidence that isometric measures at a single joint angle are not sufficient in generalizing activation of an entire muscle group for dynamic movements. CARs are significantly affected by joint angle and mode of contraction.     

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.     

Test-retest reliability of isokinetic knee extension and flexion torque measurements in persons with spastic hemiparesis

The purpose of this study was to evaluate and compare the test-retest reliability of isokinetic torque measurements in the involved and uninvolved knee musculature of 20 subjects with spastic hemiparesis. An isokinetic dynamometer was used to measure maximal voluntary knee extension and flexion at 60 degrees and 120 degrees/s. Peak torque (PT) and average peak torque (APT) data were collected from five repetitions on two separate occasions. Average peak torque was defined as the mean of the PT values obtained during each of the five repetitions. Spasticity was measured in the involved knee musculature prior to isokinetic testing using the Ashworth Scale. Pearson Product-Moment Correlation Coefficients and intraclass correlation coefficients (ICCs) were high (greater than or equal to .90) for both knees for PT and APT at both angular velocities. No clinically meaningful differences were found between the Pearson correlation coefficients and the ICCs of the involved versus the uninvolved knee for any testing conditions. We concluded that isokinetic evaluation of torque, as measured by PT and APT in subjects with spastic hemiparesis, can yield reliable results in both extremities.     

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.     

Reliability of measurements of concentric and eccentric isokinetic loading

The purpose of this study was to assess the reliability of a method for testing peak torque and work output of the knee extensor muscle during concentric and eccentric loading at three velocities of exercise (60 degrees, 120 degrees, and 180 degrees/sec). Fourteen healthy men (23-32 years of age) performed exercises of the quadriceps femoris muscles during concentric and eccentric loading, with a five-second pause between each contraction. Three different tests were performed on different occasions. The first exercise session was a practice session, and the next two sessions were established to collect data in a test-retest format. Peak torque and work were measured for the two testing sessions. The results of this study demonstrated that with a very specific protocol, the reliability of concentric peak torque and work measurements was excellent at 60 degrees and 120 degrees/sec and good at 180 degrees/sec. In contrast, reliability of eccentric peak torque and work measurements was good at 120 degrees and 180 degrees/sec but low at 60 degrees/sec.     

Smartphone goniometer has excellent reliability between novice and experienced physical therapists in assessing knee range of motion

IntroductionSmartphone app-based goniometer (SG) are emerging as an alternative to Universal Goniometers (UG) in assessing joint range of motion (ROM). This study examined whether the experience level of examiner affected the reliability of assessing knee flexion (KF) and knee extension (KE) ROM using UG and SG.MethodsParticipants with osteoarthritis of the knee or following total knee replacement were recruited. KF and KE ROM using UG and SG were assessed twice by an experienced physical therapist (PT) and a student PT (SPT). Intraclass correlation coefficients (ICC) examined the interrater (experienced PT vs SPT) and intrarater reliabilities (for experienced PT and SPT) in assessing KF and KE ROM for UG and SG. Concurrent relationships were examined between the knee ROM with pain and physical function using Pearson Correlation Coefficient (r).ResultsThe interrater reliability in assessing KF and KE ROM was excellent (ICC>0.90) between novice and experienced examiners. The standard error of measurement (SEM) for novice examiner in assessing KF was 1° and 2° while using UG and SG respectively; whereas the SEM for experienced examiner in assessing KF was 1° irrespective of which device was used. The concurrent relationships between KF and KE ROM with measures of pain and function were divergent (moderate to low correlations; r <0.7; p > 0.05).ConclusionBoth UG and SG have smaller measurement error in assessing KF and KE ROM irrespective of experience level of examiner and therefore no one tool is superior than the other for assessing knee ROM in clinical practice.     

Electrically elicited fatigue test of the quadriceps femoris muscle. Description and reliability

The purposes of this study were to develop an electrically elicited fatigue test (EEFT) that uses electrically elicited isometric muscle contractions and to examine the reliability of this test on a group of healthy individuals. Fifteen subjects were tested on two occasions, one week apart. The subjects were seated and the left leg secured to an isokinetic dynamometer with the knee positioned at 45 degrees of flexion. Maximum voluntary isometric contraction (MVIC) of the quadriceps femoris muscle was obtained and resultant knee extension torque was recorded. The quadriceps femoris muscle then was stimulated 50 times at the current level that elicited a knee extension torque level equal to 60% of that obtained during the MVIC. Percentages of decline in torque were calculated. Test-retest reliability indexes were calculated for the means of contractions 21 to 25 (r = .82, ICC = .83) and for contractions 46 to 50 (r = .92, ICC = .82). The EEFT was found to be reliable and may provide a clinically applicable means of measuring peripheral muscle fatigue.     

Test-retest reliability of isokinetic dynamometry for the assessment of spasticity of the knee flexors and knee extensors in children with cerebral palsy

OBJECTIVE: To assess test-retest reliability of the peak resistance torque and slope of work methods of spasticity measurement of the knee flexors and extensors in children with cerebral palsy (CP). DESIGN: Test-retest reliability study. SETTING: Pediatric orthopedic hospital. PARTICIPANTS: Fifteen children with CP. INTERVENTION: Knee extensor and flexor spasticity was assessed with an isokinetic dynamometer using passive movements at 15 degrees, 90 degrees, and 180 degrees/s taken 1 hour apart. MAIN OUTCOME MEASURES: Peak resistive torque and work were calculated. The relative and absolute test-retest reliability was calculated by using intraclass correlation coefficients (ICCs) and Bland-Altman plots, respectively. RESULTS: Relative reliability was good (ICC>.75) for slope-of-work and peak resistance torque measurements at a velocity of 180 degrees/s, whereas reliability of peak torque measurements was decreased (ICC<.51) at slower velocities for both muscle groups. The 95% limits of agreement of Bland-Altman plots contained most data points for both methods, but the width of the limits of agreement were wide. CONCLUSIONS: The measurement of spasticity of the knee extensors and flexors in children with CP using peak-resistance torque at 180 degrees/s and the slope of work method has acceptable relative test-retest reliability. However, the absolute reliability of spasticity data should be considered cautiously.     

Reliability of goniometric measurements and visual estimates of knee range of motion obtained in a clinical setting

The purpose of this study was to examine the intratester and intertester reliability for goniometric measurements of knee flexion and extension passive range of motion (PROM). In addition, parallel-forms reliability for PROM measurements of the knee obtained by use of a goniometer and by visual estimation was examined. The intertester reliability for visual estimates of the PROM of the knee was also examined. Repeated measurements were obtained on 43 patients in a clinical setting. The intraclass correlation coefficients (ICCs) for intratester reliability of measurements obtained with a goniometer were .99 for flexion and .98 for extension. Intertester reliability for measurements obtained with a goniometer was .90 for flexion and .86 for extension. The ICCs for parallel-forms reliability for measurements obtained with a goniometer and by visual estimation ranged from .82 to .94. The intertester reliability for measurements obtained by visual estimation was .83 for flexion and .82 for extension. Results suggest clinicians should use a goniometer to take repeated PROM measurements of a patient's knee to minimize the error associated with these measurements.     

The effect of different knee angles on knee volume measured with the Perometer device in uninjured subjects

The Perometer is an optoelectronic device used to calculate limb volume. However, knee angle effect on knee volume during a Perometer measurement has not been reported. This could be a potential confounding factor in assessing knee volume in subjects with impaired knee mobility and where volume measurements are taken over time. To address this issue, bilateral knee volume measurements were recorded from 20 uninjured subjects in seven different knee angles from 0-60 degrees flexion. All 40 knees were not measured in all seven angles because of obstruction of the measurement frame when some knees were in 50 degrees and 60 degrees flexion. Thus, the volume data was separated into three subgroups for analysis: 40 knees at knee flexion angles 0, 10, 20, 30 and 40 degrees; 36 knees at 50 degrees; and 16 knees at 60 degrees. Repeated measures analysis of variance showed a statistically significant difference between the volume measurements in the three subgroups: 0-40 degrees knee flexion [F(4,156) = 35.146, P<0.001], 50 degrees knee flexion (F(5,175) = 56.826, P<0.001] and 60 degrees knee flexion, [F(6,90) = 45.825, P<0.001]. Subsequent paired t-tests showed statistically significant [P<0.001] differences in knee volume for all angle comparisons except for 0 and 10 degrees (absolute volume difference of 1.2 ml; P = 0.772) and 0 and 20 degrees (absolute volume difference of 10.9 ml; P = 0.036) (Bonferroni adjustment applied). The absolute values of the differences that were shown to be statistically significantly different ranged from 12-47 ml for the 0-40 degrees subgroup; 39-85 ml for the 50 degrees subgroup and 35-107 ml for the 60 degrees subgroup. In conclusion, knee angle affects Perometer knee volume measurements and statistically significant differences occur as knee flexion exceeds 20 degrees with greater differences occurring as the knee is more flexed. Hence, knee angle should be reproduced in re-testing and in side-to-side comparisons when evaluating knee volume with the Perometer.     

屈膝肌群在不同起始角度下的募集特征分析

目的:探讨在不同起始角度下,股后肌群与腓肠肌群参与屈膝动作的募集程度与动员顺序,为运动训练、运动康复的运动处方设计提供建议.方法:20例健康成年男子在坐姿屈膝训练器上,以5个起始角度做负荷为1RM(1次重复最大负荷)的80％屈膝动作3次,采集其屈膝肌群的表面肌电图.结果:①在同一起始角度下,屈膝动作中各肌群的募集比例一...     

Reliability of isokinetic ankle dorsiflexor strength measurements in healthy young men and women

The purposes of this study were: (i) to determine the test-retest reliability of isokinetic ankle dorsiflexor strength measurements in young healthy adults using the Biodex dynamometer, and (ii) to examine several statistical measures for the interpretation of reliability. Thirty men and women (mean age 23 +/- 3 years) performed three maximal concentric contractions at 30 degrees/s, 60 degrees/s, 90 degrees/s, 120 degrees/s and 150 degrees/s. Reliability of peak torque, work and torque at a specific time were assessed by calculating the intraclass correlation coefficient (ICC 2,1), Pearson product moment correlation coefficient (r), standard error of the measurement (SEM), method error (ME) and coefficient of variation (CV), and by plotting the differences between observations against their means. Isokinetic tests of ankle dorsiflexor strength in healthy young adults using the Biodex dynamometer were highly reliable (ICC 0.61-0.93). It is recommended that test-retest reliability analyses include the ICC and assessments of measurement errors (SEM, ME or CV), as well as graphs to indicate any systematic variations in the data.     

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.     

Activation of vastus medialis oblique is not delayed in patients with osteoarthritis of the knee compared to asymptomatic participants during open kinetic chain activities

This study investigated whether the onset of electromyographic (EMG) activity of vastus medialis oblique (VMO) was delayed relative to that of vastus lateralis (VL) in patients with osteoarthritis (OA) of the knee compared to asymptomatic participants during open kinetic chain activities. An exploratory observational cross sectional study was carried out. Two groups were tested, symptomatic OA knee patients, diagnosed by an orthopaedic surgeon, (n=17), mean (SD) age 66.0 (7.6) years, and asymptomatic participants (n=17), 56.7 (8.6) years. Surface EMG activity of VMO and VL was measured, during concentric contractions extending the knee from 90 degrees flexion, and during maximal voluntary isometric contractions at 60 degrees knee flexion. The EMG onset times of VMO and VL were determined visually and by algorithm. The onset timing difference (OTD) between the two muscles was calculated for each subject, by subtracting the onset time of VL from VMO. Mann-Whitney U-tests revealed that the OTD between VMO and VL was not significantly different between the groups during either contraction type (both p>0.05). The results of this exploratory study may have implications for rehabilitation programmes aimed at developing preferential activation of VMO compared to VL in OA knee patients.     

Co-contraction during passive movements of the knee joint in children with cerebral palsy

BACKGROUND: Co-contraction is an impairment commonly reported in children with cerebral palsy. However, co-contraction has not been investigated during passive movements which may be used to assess spasticity in children with cerebral palsy. The purpose of this study was to examine the frequency of co-contraction and the relationship between reflex activity and co-contraction during passive movements of the knee joint in children with cerebral palsy. METHODS: Twenty children with cerebral palsy participated in this study. One set of ten continuous passive movements from 90 degrees of knee flexion to 25 degrees of knee flexion and from 25 degrees of knee flexion to 90 degrees of knee flexion was completed at 15 degrees /s, 90 degrees /s, and 180 degrees /s. The mean percentage of the range of motion of each movement and mean percentage of the number of movements which exhibited electromyographic activity of the vastus lateralis, medial hamstrings, and co-contraction were calculated for each set of movements. FINDINGS: The number of the movement repetitions and the percentage of the range of motion which exhibited co-contraction were considerable regardless of the direction and speed of motion. Significant positive correlations were found between the percentage of the passive range of motion with medial hamstrings activation, vastus lateralis activation, and co-contraction during passive movements into both knee flexion and knee extension at a velocity of 15 degrees /s, 90 degrees /s, and 180 degrees /s (P<0.001). INTERPRETATION: Co-contraction commonly occurs during passive movements of the knee in children with cerebral palsy. The presence of co-contraction may influence measurements of spasticity which use passive movements to assess spasticity.