Isokinetic Movements Research Articles

Reciprocal coactivation patterns of the medial and lateral quadriceps and hamstrings during slow, medium and high speed isokinetic movements

The effect of movement velocity and fatigue on the reciprocal coactivation of the quadriceps and hamstrings was investigated through analysis of the root mean square (RMS) and the median frequency (MDF) of surface electromyography for the vastus medialis (VM), vastus lateralis (VL), medial hamstrings (MH) and biceps femoris (BF). Fourteen subjects performed six continuous isokinetic knee extension and flexion movements at 60°, 180° and 300° s −1, and 30 continuous movements at 300° s −1 to examine muscular fatigue patterns. Statistical analyses revealed that the RMS activity of the VM displayed greater coactivation than the VL ( P<0.01) and the BF displayed greater coactivation than the MH ( P<0.0001). There was no effect of velocity on the coactivation levels of the VM, the VL, or the MH; however, there was an effect of velocity on the coactivation levels of the BF ( P<0.0001). Relative to MDF activity, the MH shifted upward as velocity increased ( P<0.01) while the BF decreased between 180 and 300° s −1 ( P<0.01). Results of the muscular fatigue test indicated that the RMS activity of the VM showed a higher degree of coactivation than the VL ( P<0.01) and the BF showed approximately three times the coactivation level of the MH ( P<0.001). The MDF of the VL and MH shifted downward as the repetitions progressed ( P<0.01) with no changes for the VM or for the BF. Results of this study suggest that during isokinetic testing, both the VM and BF have significantly greater reciprocal coactivation levels when compared to the VL and MH, respectively. In addition, these results suggest that motor unit recruitment patterns of the VM and VL and the MH and BF differ with regard to the effects of velocity and fatigue.

Determination of Angles of Awkward Wrist Postures for Wrist and Grasp Force

Neutral position of the wrist has been recommended because this posture can allow the greatest hand force and avoid musculoskeletal injury or illness. Most postural analyses have categorized wrist positions into three levels such as 0, 15 or 16, and 45 degrees to decide the severity of awkward wrist postures (McAtamney and Corlett, 1993). The purpose of this study is to verify the change of wrist force with simultaneous grasp force at every two degrees of wrist angle under isokinetic wrist movements at low speeds. Moreover, specific wrist angles may be recommended to define awkward wrist postures in terms of wrist and grasp maximum voluntary contractions. Twenty-five male subjects voluntarily participated in the study. The wrist and grasp forces were the dependent variables. The independent variables were three levels of speed (10 deg/sec, 20 deg/sec, and 30 deg/sec) and two levels of wrist motions (flexion and extension). Each trial was divided into 2-second exertions to reduce the effect of the forearm fatigue. With the specially designed isokinetic wrist dynamometer, each subject followed the American Society of Hand Therapists standard (Fess and Moran, 1981) and was tested in a random order with two-minute rest periods between trials. The results of analysis of variance performed for the wrist force revealed that there were significant differences in angle, speed, and wrist motion (p = 0.0001, p = 0.0001, and p = 0.0001, respectively). According to Tukey tests, the range of angles from 66 degrees of flexion to 26 degrees of extension were in the same grouping that included the maximum wrist force that was 49.674N at 18 degrees of flexion. The mean wrist force of 30 deg/sec (38.4657N) was lower than those of the others (43.2751N for 10 deg/sec and 41.3768N for 20 deg/sec). Also, the mean wrist force of flexion (38.4657N) was greater that that of extension (29.599N). The results of ANOVA performed for the grasp force showed that there were significant differences in angle and speed (p = 0.0001 and p = 0.0001). Tukey tests showed that the wrist angle from 58 degrees of flexion to 22 degrees of extension was in the same group that included the maximum grasp force that was 285.45N at 24 degrees of flexion. The mean grasp force of the 10 deg/sec (231.025N) were higher than the other speeds (204.931N for 20 deg/sec and 200.215N for 30 deg/sec). Both wrist and grasp forces decreased as the wrist angle deviated far from the neutral position in either direction. The study identified the neutral wrist position range in terms of wrist and grasp forces. According to the results, the wrist position can be divided into three categories. First, the neutral range of the wrist is from 58 degrees of flexion to 22 degrees of extension. Second, a reasonably neutral range can be from 70 to 58 degrees of flexion and from 22 to 70 degrees of extension. Third, awkward posture of the wrist is from 70 degrees flexion to the maximum for that subject and from 70 degrees of extension to the maximum range for that subject. These results broaden the currently accepted neutral range and has major implications for postural analysis and the definition of awkward wrist angles.

Motor Skill Learning of Concentric and Eccentric Isokinetic Movements in Older Adults

Neuromuscular adaptation at the onset of resisted exercise can be observed as increases in torque and surface electromyography. The effect of learning the motor task has been hypothesized to contribute to these early increases, especially for older people. Thus, the purpose of this study was to investigate the facilitatory effects of practice on motor performance in older adults during short-term isokinetic training of the ankle dorsiflexors (DF). Twenty-eight men and women (M = 76.3 +/- 4.6 years) volunteered for a 2-week, 3-days/week strength training program. They were tested in a sitting position on a KinCom isokinetic dynamom eter at 30, 90, and 180° s-1 through 40° of DF movement (concentric and eccentric contractions). Criterion curves of lever arm angle patterns were cross-correlated with subject-generated angle patterns, showing significantly better correlations on posttest versus baseline. Smoothness and proficiency of muscle contraction improved with practice by fewer hesitations in movement and increased ability to change between concentric and eccentric muscle contractions. Increased agonist electromyography and torque were hypothesized to be secondary to greater neural drive and/or synchronization of motor unit firing rate and/or recruitment during maximal voluntary contraction, improved coordination, and adapted neural control of concentric and eccentric muscle contraction.

Reliability of torque measurements during passive isokinetic knee movements in healthy subjects.

In the literature, few data are available about the reliability of torque measured during passive isokinetic knee movements. This study investigated the consistency of torque measurements during passive knee movements at 60, 180 and 300 degrees/second in 30 healthy subjects. Intraclass correlation values ranged between 0.78 and 0.92 when the results of two consecutive tests were compared. When retests were performed after repositioning the subjects, intraclass correlation values ranged between 0.43 and 0.87. These findings indicate the necessity for meticulous standardization of the test situation. Series of 10 consecutive movements, specifically repetitions of knee flexion at 180 and 300 degrees/second, indicated that torque measurements during the first two movements were less stable than those following. A concurrent change in electromyographic activity in the rectus femoris muscle suggested that these torque variations resulted from habituation of the stretch reflex.

Inertial effects on moment development during isokinetic concentric knee extension testing.

Two group pre-test post-test design was used with 2 isokinetic dynamometers in a laboratory setting. To evaluate the inertial effects on moment measurements during the initial acceleration period of concentric isokinetic knee extension. Torque acceleration energy is a controversial measure of muscle "explosive power." Moments due to acceleration during the initial period of isokinetic movements have been ignored in the majority of isokinetic studies. These inertial effects were assessed at various angular velocities measuring the work production at the initial 0.125 second on a Biodex and a Lido dynamometer. Four women (age, 23.33 +/- 2.49 years) and 5 men (age, 26.00 +/- 2.63 years) were tested on Biodex. A different group of 9 men (age, 23.4 +/- 3.41 years, height, 1.77 +/- 1.02 meters, and mass, 74 +/- 8.26 kg) was tested on the Lido. Joint moment was calculated by including moments associated with the angular acceleration of the lower limb and the lever arm. Torque acceleration energy was significantly greater after correction for inertial effects compared with uncorrected measures at moderate (165 and 180 deg/s) and high velocities (300 deg/s) on both dynamometers. In cases where moment development in the initial 0.125 second of an isokinetic movement is measured, it would be better to use slow velocities where inertial effects are minimum. At high angular velocities inertial correction is essential to acquire valid moment measurements and conclusions about muscle and joint function.

Torque variations during repeated passive isokinetic movements of the knee in subjects with Parkinson's disease and healthy control subjects.

The purpose of this study was to quantify response variations during isokinetic passive movements of the knee in subjects with Parkinson's disease. Parkinsonian patients demonstrated a greater decrease of resistive torque compared to healthy control subjects, particularly in tests at higher velocities and during knee flexion movements. Responses were influenced by electromyographic activity in stretched and shortened muscle groups and also by mechanical factors. The results indicate that repetition of movements needs to be taken into account when measuring hypertonia in parkinsonian subjects.

The Effect of PCL Injury on Muscle Performance

Studies on the effect of posterior cruciate ligament (PCL) injury on muscle performance have demonstrated that the normal PCL accommodates sensory nerve endings with capabilities that provide the central nervous system with information about characteristics of movement and position-related stretches of the PCL. Concerning the effect of PCL injury on performance of the quadriceps and hamstrings, there is disagreement in the literature. If there is an effect in the PCL-deficient knee, it is not as simple as that in the anterior cruciate ligament (ACL)-deficient knee. Electromyographic studies have demonstrated that the gastrocnemius muscle is significantly activated during walking and isokinetic motion in the involved knee, as compared with the uninvolved knee. Results of a gait-analytic study suggested that there are significant differences in gait cycle between PCL-deficient and normal knees. These phenomena might be part of the compensatory mechanism in PCL-deficient knees, but the data on the effect of PCL injury on muscle performance remain insufficient at the present time.

Viscous properties of human muscle during contraction

The purpose of this study was to determine viscous properties of human muscle during plantarflexion efforts. Experiments were performed on 17 subjects with an ankle ergometer allowing sinusoidal oscillations during isometric contractions and isokinetic movements. Sinusoidal oscillations led to the expression of (i) Bode diagrams of the musculo-articular system allowing the determination of a damping coefficient ( B bode); and (ii) a viscous coefficient ( B sin) using an adaptation of Hill’s equation to sinusoidal oscillations. Isokinetic movements led to torque–velocity relationships. They showed a fall in torque associated to an increase in angular velocity what was quantified by calculating a damping coefficient ( B iso). Both experiments gave consistent results indicating that B bode was the lowest viscous parameter. This difference is discussed in terms of (i) “analog” viscosity originating from muscle cross-bridges; and (ii) real mechanical damping of passive structures.

Isokinetic assessment of spasticity in subjects with traumatic spinal cord injury (ASIA A).

To assess resistance to passive isokinetic movements at specified speeds and range of motion, as a measure of muscular tonus. A group of 12 subjects with complete traumatic spinal cord injury and a group of 12 able-bodied subjects were analysed, distinguishing the level of spasticity in the SCI group. Maximum eccentric peak torque was observed in passive isokinetic flexion (F) and extension (E) knee movement in displacements of 30, 60 and 120 per second. The Student t-test showed that the average torque in the injured group was significantly higher than in the control group (F= 120 degrees per second, P<0.001). Variance analysis showed that the lower level presented lower torque levels (E=60 and 120 degrees per second, P<0.032), while those in the higher level presented higher torque levels (F and E=60 and 120 per second, P<0.032) when compared to the control group. In the control group the Student t-test (P<0.0006) showed a significantly different muscle behavior (Flexion>Extension Torque). By using isokinetic assessment it was possible to quantify hypertonic spasticity in a group of subjects with spinal cord injury, distinguishing groups with higher and lower levels of spasticity as compared to a control group.

LOWER LIMB FLEXIBILITY AND MUSCLE STRENGTH IN OSGOOD SCHLATTER DISEASE.

1819 BACKGROUND: Osgood-Schlatter Disease (OSD) is a result of microavulsions caused by traction of the patellar tendon on the tibial apophysis. We hypothesized that adolescent patients with OSD lack knee flexibility and may have an imbalance of muscle strength in the lower limbs. METHODS: 9 adolescents (mean age=11.8 yrs.) with OSD were matched for age, sex, height and weight with 9 adolescents with no known knee disease. Participants completed a questionnaire about type and frequency of sports participation. Quantitative static flexibility of the hamstring and quadriceps muscles was measured. Isokinetic knee extensor and flexor muscle strength was measured at speeds of 90,180,&360 degrees/second using a Biodex III system dynanometer. Peak torque and total work during isokinetic movement was calculated. RESULTS: A comparison of quadriceps and hamstring flexibility by goniometer between the OSD and control groups showed similar flexibility (mean 127.4 degrees and 129.6 degrees, respectively for quadriceps and 39.8 degrees and 41.2 degrees for hamstrings, p=ns). Subjects in the OSD group who engaged in sports more than three times a week (n=7) were significantly less flexible than the remainder (n=11) of the participants (mean quadriceps flexibility 141.1 degrees vs. 128 degrees, p<0.05). Isokinetic strength testing of bilateral knee extensor and flexor muscle groups was not significantly different between the OSD and control groups. However, the ratio of knee extensor strength to knee flexor strength was greater in affected knees of OSD subjects than in knees of controls. (Mean knee extension/flexion ratio in OSD subjects 73/30 ft.lbs=2.4, in controls 78/42 ft.lbs.=1.85, p<0.05). CONCLUSION: Lack of flexibility and strength imbalance of the leg muscles is associated with OSD. While this cross-sectional study cannot determine cause and effect, training aimed at improving the flexibility and balancing the strength of the leg muscle groups in adolescents may help prevent Osgood-Schlatter disease.

Isokinetic elbow joint torques estimation from surface EMG and joint kinematic data: using an artificial neural network model

Because the relations between electromyographic signal (EMG) and anisometric joint torque remain unpredictable, the aim of this study was to determine the relations between the EMG activity and the isokinetic elbow joint torque via an artificial neural network (ANN) model. This 3-layer feed-forward network was constructed using an error back-propagation algorithm with an adaptive learning rate. The experimental validation was achieved by rectified, low-pass filtered EMG signals from the representative muscles, joint angle and joint angular velocity and measured torque. Learning with a limited set of examples allowed accurate prediction of isokinetic joint torque from novel EMG activities, joint position, joint angular velocity. Sensitivity analysis of the hidden node numbers during the learning and testing phases demonstrated that the choice of numbers of hidden node was not critical except at extreme values of those parameters. Model predictions were well correlated with the experimental data (the mean root-mean-square-difference and correlation coefficient γ in learning were 0.0290 and 0.998, respectively, and in three different speed testings were 0.1413 and 0.900, respectively). These results suggested that an ANN model can represent the relations between EMG and joint torque/moment in human isokinetic movements. The effect of different adjacent electrode sites was also evaluated and showed the location of electrodes was very important to produce errors in the ANN model.

Reciprocal Coactivation Patterns of the Lateral and Medial Quadriceps and Hamstrings during Low- and Moderate-Speed Isokinetic Movement

The purpose of this study was to examine coactivation patterns of the lateral and medial quadriceps and the lateral and medial hamstrings during low- and moderate-speed isokinetic movements. Twelve female athletes performed isokinetic knee assessments at 60 and 180°/s. Root mean square electromyographic (rmsEMG) activity and the median frequency of the EMG (mfEMG) were determined by placing bipolar surface electrodes on the vastus lateralis (VL), vastus medialis (VM), biceps femoris (BF), and medial hamstrings (MH). Results of rmsEMG indicated that the VM showed almost twice the coactivation of the VL (p &lt; .05), and that the BF showed almost four times the coactivation of the MH (p &lt; .05). Finally, differences were noted in the mfEMG (p &lt; .05), with the VM displaying different recruitment patterns at 180°/s as an agonist compared to that as an antagonist. Results indicated that when acting as antagonists, the VM and BE display the greatest EMG patterns during isokinetic knee joint movement.

ESTIMATION OF ELBOW JOINT POSITION BEFORE, DURING, AND FOLLOWING A 17-DAY SPACEFLIGHT.

1920 The ability to estimate elbow joint position was tested in four male astronauts before (-30 and -12 days), during (1, 4, 9, and 15 days), and after(+1, +5, +9, and +16 days) a 17-day spaceflight (STS-78). Subjects were asked to estimate 90 ° or 135 ° joint angles during passive (relaxed) and active (10% maximal agonist effort) isokinetic extension (EXT) and flexion(FLX). Subjects also estimated these joint positions during low resistance isotonic EXT. For each angle, 6 (isokinetic) and 3 (isotonic) trials were requested in random order. Across all test conditions, the mean angle estimate ranges were 93 °-118 ° and 119 °-152 ° for requested angles of 90 ° and 135 °, respectively. Subjects overestimated the 90 ° position across all conditions, whereas the accuracy of the 135 ° estimate varied. Angle estimates were most accurate during isokinetic FLX for 90 °(mean error +9.8 °) and isokinetic EXT for 135 ° (mean error +0.7°). No differences occurred between passive vs. active isokinetic EXT or FLX. Estimates of each joint angle during isokinetic EXT were less than isotonic EXT, but greater than isokinetic FLX (P<0.05). During spaceflight, joint angle estimates were lower during isokinetic FLX and EXT for 90 °(P<0.05) and 135 ° (P≤0.10) compared to preflight. Spaceflight also decreased angle estimates during isotonic FLX and EXT (P<0.05). Elbow angle estimates had returned to preflight values one day after return to 1G. These data demonstrate that elbow joint angle estimation was: 1) decreased during spaceflight, particularly for isotonic conditions 2) rapidly restored to preflight values upon return to 1G; and 3) not changed by low level agonist muscle exertion during isokinetic movements. These data indicate that the proprioception of elbow joint position is altered by microgravity, but rapidly readapts to preflight control values after return to 1G.

Effect of movement velocity on the median frequency of the electromyographic activity of the quadriceps and hamstrings during isokinetic testing

The purpose of this study was two-fold: 1) to examine the median frequency of the electromyographic activity (mfEMG) of the quadriceps and hamstrings during isokinetic movements at 60, 180 and 300° . s -1 and 2) to examine the changes in the mfEMG with fatigue at 300° . s -1 . Fourteen female athletes had their dominant limb tested on a Cybex II+ isokinetic dynamometer (Cybex, Ronkonkoma, NY). The mfEMG of the quadriceps and hamstring muscle groups was determined by placing bipolar surface electrodes on the vastus lateralis, vastus medialis, biceps femoris, and medial hamstrings. Repeated measures ANOVA indicated no effect of movement velocity on the mfEMG of the quadriceps. Significant differences were noted however in the mfEMG of the hamstrings with the higher movement velocities effecting significant upward shifts in the mfEMG. Significant differences were also noted in the mfEMG of both the quadriceps and the hamstrings within the 300° . s -1 trials with the mfEMG shifting downward as the muscles fatigued. These results suggest that there is a difference in motor recruitment strategies for the hamstrings between low, moderate and high speed isokinetic activity and for the quadriceps and the hamstrings during high velocity movement.

Muscular endurance in long-term IDDM patients.

To determine the short-term muscular endurance and working capacity of leg muscles in long-term IDDM patients in relation to neuropathic complications, muscle strength, and metabolic control. The muscular endurance of extensors and flexors at the ankle and knee was assessed in 44 IDDM patients and in 44 matched control subjects during 30 maximal isokinetic movements. The endurance index was the work performance of the last 5 movements relative to the first 5 movements. Total work was the summated work of all movements. All patients underwent a neurological evaluation, nerve conduction studies, and quantitative sensory tests. The combined endurance index of the ankle extensors and flexors was 70% (51-88) (median [range]) in the diabetic group and 65% (55-82) in the control group (P < 0.01). For knee extensors and flexors the combined endurance index was 65% (55-103) for the diabetic patients and 63% (48-75) in the control subjects (P < 0.01). The endurance index related neither to the severity of neuropathy nor to the metabolic control (blood glucose and HbA1c) for any of the muscle groups. Diabetic patients had reduced strength of all muscle groups (14-24%, P < 0.02) and impaired total work performance (15-20%, P < 0.01) for ankle movements. Long-term IDDM patients have increased endurance but reduced strength and work performance of leg muscles. The combined effect of the motor abnormalities is suggested to give rise to functional impairment, including an increased risk of falls and injuries.

A mechanical device for studying mechanical properties of human muscles in vivo

A mechanical device, primarily devoted to biomechanical studies of human calf muscles during microgravity experiments is presented. It allows investigation of both contractile and visco-elastic properties of musculo-articular systems using, respectively, isokinetic movements, quick-release tests and sinusoidal perturbations. This device is a specifically designed ergometer associated to an experimental protocol designed for pre- and post-flight tests. The protocol was evaluated on 22 healthy subjects and typical results are briefly presented. Preliminary results are discussed in terms of agreement with currently available data and a detailed evaluation of test-retest measurements is provided for quick-release experiments. Complementary investigations are suggested and potential fields of research are indicated.

Effect of ankle position on knee flexor and extensor torque

The purpose of this study was to examine the effect of ankle position on knee flexor and extensor torque at 60 and 180 o/s. Twelve female athletes had their dominant and non-dominant limb tested on a Cybex II + dynamometer (Cybex, Ronkonkoma, NY) under two conditions: with the ankle plantarflexed and dorsiflexed. Paired t-tests showed no statistical differences in knee extensor torque. Significant differences were noted in knee flexor torque at both 60 (P < 0.05) and 180 (P < O.Ol)°/s with the greatest torque being seen with the ankle in the dorsiflexed position. These results suggest that ankle position affects knee flexor torque during open chain isokinetic movements. Copyright © 1996 Elsevier Science Ireland Ltd.

Knee extension dynamometer: a new device for dynamic isokinetic magnetic resonance spectroscopy experiments.

In the present study we introduce a new device for exercise magnetic resonance spectroscopy (MRS). It operates in a standard whole-body scanner. Mechanical exertion unit allows maximal 10 degrees to 15 degrees short-arc knee extensions. The device operates hydraulically and is based on isokinetic movement. The force and work conducted are automatically controlled by the electronic control and computer unit. A small surface coil placed on the vastus medialis muscle allows the collection of spectra without interfering spectra from nearby resting muscles. The force used for the extensions can be followed simultaneously as a curve on the screen in the operator's room and the data is transferred to a personal computer for later analysis. Total work and fatigue percentage are also calculated by the device. It also allows the use of different isokinetic exercise protocols. The measurements of force proved reliable in repeat measurements using an isokinetic test device as a control. This device has been used clinically for over a year, is easy to operate, and offers reliable measurements. It is well suited to trials where muscle energy states versus time are followed since it allows noninvasive simultaneous quantification of muscle performance and collecting MRS spectra at rest, during exercise, and in the recovery phase.

Muscle Torque Relationships Between Hand-Held Dynamometry and Isokinetic Measurements in Children Ages 9 to 11

This study examined torque relationships of the knee flexors and extensors in 18 boys and 7 girls (a) to evaluate whether isometric torque measures obtained with the NMMT could predict corresponding dynamic torque measures obtained with the Cybex II isokinetic dynamometer and (b) to evaluate the effects of joint angular velocity and joint angel of torque measurement on torque values. The children performed maximal isometric contractions at joint angles of 30 and 60° of knee flexion, and maximal isokinetic movements at angular velocities of 60, 120, and 180° · s−1. Correlation coefficients demonstrated that isometric strength measurements could predict low-velocity dynamic strength fairly well, with no loss in accuracy. ANOVA indicated a significant interaction effect for muscle group and angular velocity (p < 0.0001). Post hoc analysis indicated that, in general, torque values were significantly higher at lower angular velocities that at higher angular velocities of joint movement on the Cybex II, and that extensor muscle strength was greater than flexor muscle strength. Results suggest that knee flexor and extensor isometric strength measures obtained with the NMMT can predict low velocity dynamic strength of these muscle groups.

Isokinetic muscle performance after anterior cruciate ligament surgery. Long-term results and outcome predicting factors after primary surgery and late-phase reconstruction.

The purpose of this study was to evaluate the long-term isokinetic muscle performance after ACL surgery and to analyze by a multiple stepwise regression which factors (if any) predict the overall outcome. The study subjects were 119 patients who had a complete rupture of the ACL and had been treated surgically at the Tampere University Hospital between 1981 and 1990. They were divided into the acute group (N = 62) and into the chronic group (N = 57) according to the time delay between the injury and the ACL surgery. The isokinetic strength measurements of the quadriceps and hamstring muscles were performed on average 4 years after the operation using Cybex II and Cybex 6000 dynamometers (Lumex Inc., Ronkokoma, NY, USA). The peak torques were determined at speeds of 60 and 180 degrees/s and the peak work at speed of 180 degrees/s. The measurements revealed that after the ACL surgery there was still a considerable thigh muscle strength deficit especially in extension of the injured extremity, the average extension strength deficit ranging from 9 to 20%. The extension strength deficit was significantly more prominent in the chronic (18-20%) than in the acute group (9-15%). The extension strength deficit was significantly greater ar the slower (15-20%) than higher (9-18%) speed of the isokinetic movement. In both the acute and chronic groups, a multiple stepwise regression analysis indicated that patellofemoral pain and flexion deficit of the knee were the factors that most frequently and significantly associated with the strength deficits. At the higher speed of the isokinetic movement, these two factors accounted 20% and 21% for the variation seen in the quadriceps strength deficit of the acute group and the chronic group. No correlation could be found between age, sex, height, weight, body mass index, length of the follow-up time, injury type, athletic activity level, immobilization method, knee stability, and the isokinetic muscular performance.