Isokinetic Movements Research Articles

Time/frequency events of surface mechanomyographic signals resolved by nonlinearly scaled wavelets

The purpose of this investigation is to introduce a wavelet analysis designed for analyzing short events reflecting bursts of muscle activity in non-stationary mechanomyographic (MMG) signals. A filter bank of eleven nonlinearly scaled wavelets that maintain the optimal combination of time and frequency resolution across the frequency range of MMG signals (5–100 Hz) was used for the analysis. A comparison with the short-time Fourier transform, Wigner-Ville transform and continuous wavelet transform using a test signal with known time–frequency characteristics showed that the MMG wavelet analysis resolved the intensity, timing, and frequencies of events in a more distinct way without overemphasizing high or low frequencies or generating interference terms. The analysis was used to process MMG signals from the vastus lateralis, rectus femoris, and vastus medialis muscles obtained during maximal concentric and eccentric isokinetic movements. Muscular events were observed that were precisely located in time and frequency in a muscle-specific way, thereby showing periods of synergistic contractions of the quadriceps muscles. The MMG wavelet spectra showed different spectral bands for concentric and eccentric isokinetic movements. In addition, the high and low frequency bands seemed to be activated independently during the isokinetic movement. What generates these bands is not yet known, however, the MMG wavelet analysis was able to resolve them, and is therefore applicable to non-stationary MMG signals.

Agonist muscle activity and antagonist muscle co-activity levels during standardized isotonic and isokinetic knee extensions

This study aimed to analyze the effects of the contraction mode (isotonic vs. isokinetic concentric conditions), the joint angle and the investigated muscle on agonist muscle activity and antagonist muscle co-activity during standardized knee extensions. Twelve healthy adult subjects performed three sets of isotonic knee extensions at 40% of their maximal voluntary isometric torque followed by three sets of maximal isokinetic knee extensions on an isokinetic dynamometer. For each set, the mean angular velocity and the total external amount of work performed were standardized during the two contraction modes. Surface electromyographic activity of vastus lateralis (VL), vastus medialis (VM), rectus femoris (RF), semitendinosus (ST) and biceps femoris (BF) muscles was recorded. Root mean square values were then calculated for each 10° between 85° and 45° of knee extension (0° = horizontal position). Results show that agonist muscle activity and antagonist muscle co-activity levels are significantly greater in isotonic mode compared to isokinetic mode. Quadriceps activity and hamstrings co-activity are significantly lower at knee extended position in both contraction modes. Considering agonist muscles, VL reveals a specific pattern of activity compared to VM and RF; whereas considering hamstring muscles, BF shows a significantly higher co-activity than ST in both contraction modes. Results of this study confirmed our hypothesis that higher quadriceps activity is required during isotonic movements compared to isokinetic movements leading to a higher hamstrings co-activity.

下肢運動療法支援バイオフィードバックマニピュレータの開発

Although equipments that support physical therapy have been developed, there are few types of equipment to improve quality of physical therapy. This paper proposes a new concept of robotic biofeedback exercise equipment that displays human muscle force during training. The concept tries to have therapeutic value through grasping of condition for trainee during exercise and giving an incentive to perform training. The equipment is not only for convalescent patients but also for athletes and healthy persons with a physical trouble. The manipulator is designed to support lower limb rehabilitation of knee and hip joints in sagittal plane, where a 3-degrees-of-freedom manipulator is adopted in order to realize low height equipment. Since the manipulator has redundant degree of freedom, collision avoidance is performed by a controller based on acceleration control by disturbance observer. Moreover, simultaneous isokinetic movement for knee and hip joints that has an adjustment capability of maximum speed and time constant is realized in order to perform safe training by isokinetic muscular contraction. Desired motion is realized experimentally by the proposed manipulator.

Analyses of Isokinetic and Closed Chain Movements for Hamstring Reciprocal Coactivation

Researchers have postulated that coactivation of the hamstrings during active knee extension assists the anterior cruciate ligament in maintaining knee joint stability by exerting an opposing force to anterior tibial translation. To compare the reciprocal coactivation of the hamstrings while performing low and high velocity isokinetic movements and two closed chain movements. Within subject's comparison of isokinetic and closed chain exercises. Biomechanics laboratory utilizing a Cybex norm isokinetic dynamometer and Biopac Data Collection system. 12 healthy women. The root mean square of the Electromyogram (rmsEMG) was used as a measure of overall muscle activity. The rmsEMG for hamstring coactivation during knee extension showed significant differences between the isokinetic movements and the closed chain exercises with greater coactivation when performing the isokinetic movements. In addition, greater activity was seen at the higher isokinetic velocity and during the one legged squat. These results suggest isokinetic movements, particularly at high speed, can more effectively increase the coactivation activity of the hamstrings when compared to two closed chain activities.

Isokinetic muscle testing for weak patients suffering from neuromuscular disorders: A reliability study

Precise, sensitive muscle strength testing methods are needed to investigate muscle function in patients with neuromuscular disorders (NMD). Here, we describe an isokinetic knee flexor and extensor testing procedure using the Biodex 3 ®’s continuous passive motion (CPM) mode. The torque values recorded during passive isokinetic motion were subtracted from the torque values obtained for the same movement with maximal, concentric effort. The aims of the present study were to (i) evaluate the method’s reliability in NMD patients presenting mild to severe muscle weakness and (ii) study the relationship between manual muscle testing (MMT) and isokinetic dynamometry. The fifteen participating patients were tested twice; the respective intraclass correlation coefficients (ICCs) for the two sessions ranged from 0.91 to 0.99 for the peak torque, work and power and from 0.50 to 0.90 for the angle at peak torque. The Spearman rho correlation coefficients comparing isokinetic values and MMT values ranged from 0.67 to 0.74 ( p < 0.01). This reliable, dynamic method appears to be of great value in NMD evaluation when sensitive strength measurement at the knee is required.

Measurement of the effect of hamstring muscle force on knee cruciate ligament loading patterns during simulated extension motions: An in vitro study

Background: The objective of this study was to investigate dynamically the load on the cruciate ligaments and the effect of simulated co-contraction of the hamstrings muscles on quadriceps force and load on the cruciate ligaments. Methods: Load transducers were fixed in the fibers of the anterior and posterior cruciate ligament of seven knee specimens. Isokinetic extension motions applying an extension moment of 31 Nm, representing an extension moment capable by healthy human volunteers in isokinetic extension tests, were simulated in a knee simulator from 120 ◦ to full knee extension. Quadriceps force and load on the cruciate ligaments were measured in the absence and presence of a 200 N hamstrings co-contraction. Results: Quadriceps force significantly ( p =0 .04) increased under the application of hamstrings co-contraction. Anterior cruciate ligament load significantly increased below 20 ◦ knee flexion up to 161 N and was significantly ( p =0 .04) reduced to 29 N under hamstrings co-contraction at full knee extension. Posterior cruciate ligament load without hamstrings co-contraction showed a maximum load at 112 ◦ knee flexion of 38 N, reducing to knee extension and was not significantly increased ( p =0 .20) under hamstrings co-contraction, showing a maximum load of 66 N near knee flexion. Conclusions: This dynamic in vitro study revealed the dependency of anterior cruciate ligament load on knee flexion angle during an isokinetic extension cycle. With a co-contraction of hamstring muscles the peak load on the anterior cruciate ligament was significantly decreased in knee extension with a non significant concomitant increase of posterior cruciate load at knee flexion. These findings have implications for graft donor site selection and postoperative rehabilitation, e.g. after anterior cruciate ligament reconstructions.

Isomed 2000을 이용한 고등학교 테니스 선수 서브동작의 어깨관절 회전력과 근동원 양상 분석

The purpose of this study was to analyze the shoulder joint torque and muscle pattern performing as Tennis serve by Isokinetic motions on Isomed 2000. The subject, who was 5 males Korean national high school tennis players. By analyzing the flexion/extension of the shoulder, the peak torque of the internal/external rotation motion(at 60,180 and 300 degree/sec) at peak torque degree, the weight, peak torque, and power. combined with the timing of the electrode of the attached trapezius and posterior deltoid at the three part. From the data analysis & discussion the following conclusions were drawn. When doing a shoulder extension, the peak torque can be widely seen at 60degree per second. However the degree may be different depending on angular velocity. When doing an internal rotation at 90degree abduction, peak torque per weight was seen at 60degree per second. The degree of peak torque was at 31.6-44.2 and peak power was faster when angular velocity was increased. The aspect of muscle pattern was seen more at the internal rotation in the 90degree abduction rather than the shoulder extension. However the angular velocity was not influenced by muscle mobilization(in order of anterior deltoid, posterior deltoid and trapezius. To properly apply the above conclusion, when tennis players serve it is better the elbow be impacted by the extension. when doing isokinetic motion it is better to increase angular velocity and improve muscle power. also the anterior deltoid amongst the shoulder muscle should be improved to develop serve speed.

Veränderungen der muskulären Leistungsfähigkeit bei Trägern von Kniegelenkstotalendoprothesen

AIM: The purpose of this study was to compare muscle torque during isokinetic knee movements of patients after total knee arthroplasty (TKA) with a similar healthy group. METHOD: 43 patients were examined 3 years after primary total knee arthroplasty with an isokinetic dynamometer (Cybex 340). Torque measurements were evaluated for extension and flexion with 4 different velocities. The results were compared with a group of 43 people without knee disease. Bouth groups consist of 29 women and 14 men. The mean age was also comparable (66.4 vs. 65.8 years). RESULTS: A mean peak torque of 65.9 Nm was measured during extension with low velocity (60°/s) in the group of patients with TKA - 80.7 % of the control group (p = 0.043). At the highest velocity (180°/s) the patients produced 30.2 Nm. This was 72.8 % of the control group (difference statistically significant, p = 0.006). No differences were found in the Extension/Flexion ratio between the two groups. CONCLUSION: The deficites of knee strength in patients after TKA are more distinct in high velocities of motion.

Ankle joint evertor–invertor muscle torque ratio decrease due to recurrent lateral ligament sprains

Objective. To determine an ankle inversion–eversion movement range part where evertor/invertor muscles torque ratio is altered after recurrent ankle lateral ligament sprains. Design. The ankle evertor/invertor muscles torque ratios were determined in the different range parts of angular positions by the muscle isokinetic movements. Background. It is important to determine the movement range part where the evertor muscle weakness after the ankle lateral ligament sprains is more expressed and a repeated trauma of the lateral ligaments is more probable. Methods. Twenty-eight male handball players participated in the tests using an ankle isokinetic inversion–eversion movement investigation dynamometer system. Thirty-three ankle joints were uninjured, but 23 underwent recurrent lateral ligament sprains. Results. The ankle evertor/invertor muscles torque ratio for the sprained ankles was significantly lower in comparison with the uninjured joints in inversion positions at 50° and 60° of the range of movements in all applied velocities, except the slowest movement (30°/s). Conclusions. The recurrent ankle lateral ligament sprains reduced the evertor/invertor muscles torque ratio in the inversion positions of the range of movements and therefore the evertor muscle weakness was more expressed in the beginning of the eversion movement. Relevance An isokinetic dynamometry allows determining the ankle evertor/invertor muscles torque ratio alteration in the different positions of the range of movements and detecting the sprained ankle evertor muscle movement range risky parts. As a result one could elaborate special training programs for the evertor muscles rehabilitation.

Effects of Stretching the Upper Limb on Throwing speed and Isokinetic Shoulder Torques

0937 Exercise is commonly preceded by warm-up and stretching routines. Although stretching has been documented to increase range of motion, recent studies have shown little effect of stretching on injury rates and adverse effects on high-force muscular performance. Strength deficits following stretching have also been found on slow isokinetic movements but not on higher velocities. PURPOSE: To determine the effects of static stretching of upper limb muscles on overarm throwing speed and isokinetic torque of shoulder internal rotators at two velocities (3.14 and 5.24 rad×s−1). METHODS: Forty subjects were randomly assigned into control and stretching groups. The experimental protocol consisted of 2 test sessions scheduled a week apart. Subjects in the experimental group performed static stretching (St) exercises to their dominant limb in one of their sessions and no stretching in the subsequent session. The order of the sessions, St or no-stretch (NSt), for the experimental subjects was randomized. Subjects in the control group did not stretch in either of their two sessions. Following warm-up and St or NSt, subjects were tested for throwing speed and concentric isokinetic torque of the shoulder internal rotation musculature at two velocities. Throwing speed was measured with a radar gun and shoulder internal rotation torques were measured with an isokinetic dynamometer. Speed and torque comparisons were made using two-way ANOVAs with repeated measures. RESULTS: Significant interactions were found for throwing speed (F = 18.96, p = .000) and isokinetic torque at 3.14 rad×s−1 (F = 5.01, p = .031), but not for isokinetic torque at 5.24 rad×s−1 (F = 4.07, p = .051). CONCLUSION: The results of this study indicated that static stretching produced a significant decrement in high-speed throwing performance and shoulder concentric torque at 3.14 rad×s−1. This result is in agreement with numerous studies that have shown stretching prior to engaging in a dynamic activity results in significant decreases in maximal muscular performance. These findings suggest that stretching prior to physical activities that contain multi-segment highspeed muscle actions, like throwing, may have a detrimental effect on performance.

The relationship between muscle cross-sectional area and strength in various isokinetic movements among soccer players

The aim of the present study was to examine the relationships between muscle cross-sectional area (CSA) and muscular strength in terms of knee extension and flexion, hip extension and flexion, and hip abduction and adduction among well-trained soccer players. Fourteen university soccer players participated in the study, who had previously been divided into two groups based on ability (Group A: above-average ability; Group B: average ability). Maximal isokinetic and concentric muscular strength was measured in knee extension/flexion, hip extension/flexion and hip abduction/adduction using an isokinetic dynamometer at 1.57 and 4.19 rad·s−1 (3.14 rad·s−1) in both the dominant and non-dominant leg. The CSAs of the thigh, gluteus muscles and iliopsoas muscles were calculated based on magnetic resonance imaging. There was no significant difference between the two groups in muscle CSA and isokinetic strength. Although there were some statistically significant differences between the dominant and non-dominant leg in terms of CSA and strength (P<0.05–0.01), these were small and negligible. Apart from a non-significant relationship between the CSAs of the adductor muscles and hip adductor strength (r<0.26, n.s.), the CSA of the other muscle groups correlated with maximal isokinetic strength (r=0.38–0.64, P<0.05). These results suggest that no difference in muscle characteristics (in terms of muscle CSA and strength) was apparent among well-trained soccer players, even between the dominant and non-dominant leg. There is also a case that the anatomical function of a single (or group of) muscle(s) may not be reflected by the strength—CSA relationship depending on the movements (such as hip adduction-adductor muscle CSA). Thus, further studies are required to develop methods to assess neuromuscular function in relation to muscle morphology among soccer players.

Study of EMG patterns and muscle strength in asymptomatic volunteers during isokinetic flexion-extension movement of the trunk

Study of EMG patterns and muscle strength in asymptomatic volunteers during isokinetic flexion-extension movement of the trunk P.-M. Dugaillya,b,c,, D. Mourauxa,b, N. Mangena, E. Brassinnea,b and P. Kleinb,c Department of Physical Therapy and Rehabilitation, Erasmus Hospital, Brussels, Belgium School of Physiotherapy and Rehabilitation, Universit e Libre de Bruxelles, Brussels, Belgium Research Unit on Manual Therapies, Universite Libre de Bruxelles, Brussels, Belgium Introduction: The objective of our study was to assess concentric muscle strength during flexion and extension of the trunk using an isokinetic device combined with analysis of back and pelvic muscle activities. Methods: Forty-one healthy volunteers, 21 females and 20 males (age: 25 ± 2 years; weight: 79 ± 8 kg; 178 ± 6 cm) participated in the study. They had no history of back or hip injuries. All subjects were familiar with concentric isokinetic back movements. Before the evaluation, the subject achieved a 10-minute bicycle warm-up and four pretest contractions. The assessment session consisted of 3 and 5 maximal concentric contractions during trunk flexion-extension at 30 ◦/sec and 120◦/sec, respectively. The entire session was performed for 2 different ranges of motion, 45 and 75 degrees. All tests were accomplished using an isokinetic dynamometer (CYBEX NORM). All electrical activities of paraspinal (PS) and gluteus maximus (GM) muscles were recorded from surface electrodes (O = 9 mm) bilaterally using a standard surface EMG procedure. Electrodes were positioned over the PS muscles at L5S1 spinal levels and over the GM at the sacrospinous ligament level. EMG data and torque were sampled at 1000 Hz and recorded using Noraxon Myosystem Software. All EMG signals were rectified and smoothed (RMS 50). All data were collected every 5 degrees from 0 degree to maximal range. Statistical analysis: Control of distribution and homogeneity of variances was conducted using Kolmogorov-Smirnoff and Levene tests. Influence of gender, velocity, movement and motion range on outcome measurements was analyzed using multivariate analysis of variance (ANOVA). Results: For each velocity males achieved significantly larger extension or flexion torque than females (p 0.05). In general, total ROM and velocity significantly influenced agonist EMG activity (p 0.89). During extension EMG recruitment patterns showed that PS and GM displayed peak activity for around 15◦ of trunk flexion while peak torque occurred around 35◦ and 65◦ for 45◦ and 75◦ ROM, respectively, at the lower speed. This observation was similar for males and females. Figure 1 illustrates torque intensity and EMG activities during flexion and extension over a 45◦ range of motion at 30◦/s ISSN 0959-3020/03/$8.00  2003 – IOS Press. All rights reserved 66 P.-M. Dugailly et al. / Abstract

Isokinetic dynamometry and electromyographic activity (sEMG) after anterior cruciate ligament reconstruction using semitendinosus and gracilis tendon autografts

Isokinetic dynamometry and electromyographic activity (sEMG) after anterior cruciate ligament reconstruction using semitendinosus and gracilis tendon autografts D. Mourauxa, P.-M. Dugaillya, E. Brassinnea and M. Vancabekeb Department of Physical Therapy and Rehabilitation, Erasmus Hospital, ULB, Brussels, Belgium Department of Orthopaedics Surgery, Brugmann Hospital, Brussels, Belgium Introduction: Quadriceps weakness after injury and reconstruction of anterior cruciate ligament (ACL) is well documented. This amyotrophy in the immediate postoperative period is related to several factors, such as decreased weight bearing, knee joint effusion, pain, harvesting of the tendon graft and neuromuscular factors [1]. The present study is designed to compare the short outcome of strength and EMG recruitment pattern of quadriceps and hamstring between 3 months postoperatively for an ACL reconstruction with hamstring tendon autografts fixed patients and a healthy control group. Methods: Thirteen healthy male students (mean age: 24 years, weight: 77 kg, height: 181 cm) participated in the study. They had no history of knee or hip injuries. They were compared to 19 patients (mean age: 31 years, weight: 80 kg, height: 180 cm) who had surgery for ACL reconstruction with hamstring tendon autografts precisely 3 months before these assessments. Patients were excluded if there were any other lesions in the same knee. In both groups the subjects were recreational athletes. All subjects were familiarized with isokinetic movements in concentric (CON) or ecTable 1 Mean ± standard deviation of quadriceps and hamstrings Peak Torque (PT). Comparison between control legs and UninvolvedInvolved legs. ∗Significant at p < 0.05 level Control Uninvolved Involved Quad PT Con 180◦/s 136 ± 23 125 ± 37 93 ± 28∗ Quad PT Con 60◦/s 193 ± 30 183 ± 30 118 ± 47∗ Ham PT Con 180◦/s 101 ± 16 89 ± 30∗ 85 ± 9∗ Ham PT Con 60◦/s 137 ± 18 118 ± 22∗ 101 ± 33∗ Ham PT Ecc 30◦/s 178 ± 13 146 ± 20∗ 113 ± 10∗ centric (ECC) contraction. The tests were performed with a CYBEX NORM consisting in 3 maximal dynamic contractions at 180◦/s and 60◦/s in CON (for both flexor and quadriceps muscles) and at 30◦/s in ECC (for flexor). During these tests, the sEMG activity was recorded from the vastus lateralis (VL), the vastus medialis (VM) the rectus femoris (RF) and the mass of the hamstring by the Noraxon Myosystem 2000. The exercices were performed at a range of motion from 0◦ to 105◦. All electrical activities were expressed in microvolt (μV). Influence of independent variables was analysed using multivariate analysis of variance

Muscle Strength Imbalance in the Hip Joint Caused by Fast Movements

Eleven male sportsmen at the age of 24.3 ± 4.5 were examined. Their hip joint flexors and extensors were tested by an “REV-9000” Technogym dynamometer system during isokinetic movements at angular velocities of 100 (low) and 200 (high) °/s. The range of hip joint movements was from 30 (in flexion) to 130° (in extension). Torque values and their ratios for hip flexors and extensors at different angular positions were obtained and compared. It is shown that, at high speeds, the flexion movement significantly raises (p < 0.001) the torque ratios of flexors and extensors in flexion positions of the hip (50 and 60°). These ratios approximately twofold exceed their values at moderate velocities. The weakness of hip joint extensors in extreme flexion positions of the hip may cause injury of this group of muscles at fast movements.

Effect of movement velocity and movement pattern on the root mean square and the median frequency of the electromyographic activity of the quadriceps during isokinetic testing

The purpose of this study was twofold: 1) compare the effect of movement velocity and movement pattern on the electromyographic activity (EMG) of the quadriceps as measured by the Root Mean Square of the electromyogram (rmsEMG) and the Median Frequency of the electromyogram (mfEMG) during isokinetic testing and 2) compare the effect of movement pattern on the torque production of the quadriceps during isokinetic testing. Fourteen healthy adult females with no known knee pathologies and familiarity with isokinetic testing performed six continuous isokinetic movements at 100 0 · s −1 , 200 0 · s −1 , 300 0 · s −1 and 400 0 · s −1 . Movements were performed in a reciprocal pattern, (maximal knee extension followed by maximal knee flexion), and a non-reciprocal pattern (maximal extension followed by relaxation of the hamstrings). Statistical analyses revealed there was a difference in the rmsEMG for the quadriceps on the effect of velocity (F =3 .2, P< 0.05) with post hoc analysis revealing significant differences in the rmsEMG between 100 and 300 0 · s −1 (F =5 .6, P< 0.05), and between 100 and 400 0 · s −1 (F =6 .7, P< 0.01) with the highest rmsEMG being seen during the slowest velocities. For the mfEMG there were significant differences when comparing the velocity of movement (F =7 .8, P< 0.001), specifically when comparing the slowest velocity 100 0 · s −1 with 200 0 ·s −1 (F =4 .9, P< 0.05), 300 0 · s −1 (F =8 .8, P< 0.005) and 400 0 · s −1 (F =2 2.7, P< 0.001) with the highest mfEMG observed at the lower velocities. No difference was noted either in EMG or torque between the reciprocal and non-reciprocal movements. The results of this study suggests that during isokinetic testing the EMG activity of the quadriceps is altered as velocity changes with regard to the rmsEMG and mfEMG. Specifically as velocity increases overall muscle activity decreases as measured by the rmsEMG. In addition as velocity increases there is a shifting toward recruitment of slower velocity muscle fibers as measured by the mfEMG. These results also suggest that movement pattern (reciprocal vs. non reciprocal) does not effect the EMG for quadriceps activity during isokinetic knee extension.

Friction between human finger flexor tendons and pulleys at high loads

A method was developed to indirectly measure friction between the flexor tendons and pulleys of the middle and ring finger in vivo. An isokinetic movement device to determine maximum force of wrist flexion, interphalangeal joint flexion (rolling in and out) and isolated proximal interphalangeal (PIP) joint flexion was built. Eccentric and concentric maximum force of these three different movements where gliding of the flexor tendon sheath was involved differently (least in wrist flexion) was measured and compared. Fifty-one hands in 26 male subjects were evaluated. The greatest difference between eccentric and concentric maximum force (29.9%) was found in flexion of the PIP joint. Differences in the rolling in and out movement (26.8%) and in wrist flexion (14.5%) were significantly smaller. The force of friction between flexor tendons and pulleys can be determined by the greater difference between eccentric and concentric maximum force provided by the same muscles in overcoming an external force during flexion of the interphalangeal joints and suggests the presence of a non-muscular force, such as friction. It constitutes of 9% of the eccentric flexion force in the PIP joint and therefore questions the low friction hypothesis at high loads.

EMG Power Frequency Spectrum Shifts during Repeated Isokinetic Knee and Arm Movements

EMG Power Frequency Spectrum Shifts during Repeated Isokinetic Knee and Arm Movements

Characteristics of velocity-controlled knee movement in patients with cervical compression myelopathy: what is the optimal rehabilitation exercise for spastic gait?

The isokinetic strength of knee extensors and flexors was measured at various controlled velocities in patients with spastic paraparesis caused by cervical compression myelopathy. To evaluate leg function objectively in patients with myelopathy. Cervical compression myelopathy causes varying degrees of spastic paresis in the legs and affects the activities of patients. However, the leg function characteristics of the patients have not been fully elucidated. Velocity-controlled voluntary knee movements were studied in 39 patients (25 men and 14 women) with compression myelopathy. Their mean age was 60.2 years (range, 44-77 years). The patients were divided into Group A (ambulation without aid, n = 22) and Group AA (ambulation with aid, n = 17). Isometric peak torque values were measured in knee flexor and extensor muscles at 60 degrees of knee flexion, and isokinetic peak torque values were determined in maximal voluntary concentric movements of these muscles at constant angle velocities of 40 degrees, 80 degrees, 120 degrees, 160 degrees, and 180 degrees per second. The relative strength (percentage of isometric peak torque value) of the isokinetic motion was calculated at each velocity. In both groups, the relative strength decreased as the velocity increased, and the degree of reduced strength in the flexors at the high velocities of 160 degrees and 180 degrees per second was significantly greater in Group AA than in Group A (P < 0.05), whereas no significant difference was found in the extensors between the groups. The results indicate that isokinetic strength at a high velocity may reflect the severity of spastic paresis in the legs resulting from compression myelopathy.

Diagnostics with isokinetic devices in shoulder measurements -- potentials and limits

The correction of muscular imbalances is assumed to be important in therapy of shoulder pathologies and muscular strengthening. However, it is not clear how these imbalances should be defined and the extent to which conclusions can be drawn, relevant to therapy and training. Statements on physiological strength ratios and deviations from these are only possible using a valid and reliable measurement. Isokinetic shoulder strength measurements can be considered validly isokinetic up to 180 °/s, Differentiation between the various types of work and movements is reliable within a test-retest variability of 15-20%. The maximum torque serves as a reliable parameter and additional information is obtained by determination of local muscle fatigue. In this context important considerations are the test method and especially positioning and fixation. However, the direct application of isokinetically determined strength values in training and rehabilitation is only possible when the exercise position agrees with the position during measurement. This is usually not the case. Since isokinetic movements are rarely if ever encountered in everyday living or sports, data obtained by these methods can hardly be used for training management and should mainly be used as a therapy control. Adequately reliable data on the strength ratio of shoulder movements can be obtained within narrow limits by isokinetic strength measurements. However, in spite of critical assessment of the methods, it is recommended that isokinetic measurements should be uniformly performed in accordance with the queries in order to guarantee comparability and interpretation. In addition stress in everyday living and sports lead to specific changes which should always be interpreted on the basis of method-specific criteria and exercise-specific movements. Taking functional-anatomical and methodical considerations into account, isokinetic measurements deliver valuable information for training and therapy within the framework of medically and scientifically founded strength diagnostics.

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° s −1, 90° s −1, 120° s −1 and 150° 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° to 40° 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° to 80° 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. Relevance Isokinetic exercise of the knee flexors induces high muscular and tibiofemoral joint forces. These tests should be applied with precaution when testing subjects with injury problems.