Isokinetics and Exercise Science - Volume 6, issue 2
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Isokinetics and Exercise Science (IES) is an international journal devoted to the study of theoretical and applied aspects of human muscle performance. Since isokinetic dynamometry constitutes the major tool in this area, the journal takes a particular interest in exploring the considerable potential of this technology.
Isokinetics and Exercise Science publishes studies associated with the methodology of muscle performance especially with respect to the issues of reproducibility and validity of testing, description of normal and pathological mechanical parameters which are derivable from muscle testing, applications in basic research topics such as motor learning paradigms and electromyography. The journal also publishes studies on applications in clinical settings and technical aspects of the various measurement systems employed in human muscle performance research.
Isokinetics and Exercise Science welcomes submissions in the form of research papers, reviews, case studies and technical reports from professionals in the fields of sports medicine, orthopaedic and neurological rehabilitation and exercise physiology.
Abstract: Traditionally, the two-headed gastrocnemius muscle has been considered as one muscle. The purpose of this study was to delineate if electromyographic (EMG) activity differences existed between the medial and lateral gastrocnemius heads, as well as torque output, in the normal right leg, during isometric plantar flexion contractions at three knee angles. Thirty volunteers, between the ages of 18–35, participated in this study. Isometric plantar flexion, with the ankle at 90° , was performed at three knee angles; 0°, 45°, and 90°. The EMG activity was measured in root-mean-square (RMS) microvolts on the Bioscope electromyographic feedback unit, and torque output was…measured on the Biodex System II Dynamometer. Results showed decreasing EMG activity of both the medial and lateral gastrocnemius heads as the knee angle changed from 0° to 90°. EMG output decreased significantly as knee flexion increased from 0° to 45° to 90° (F = 14.29, P = 0.0007). However, the pattern of EMG activity decline for medial and lateral gastrocnemius heads was significantly different (F = 4.58, P = 0.0143). Plantar flexion torque decreased significantly across the three angles (F = 94.64, P = 0.0001). It appears that the length-tension principle played a major role in the declining EMG and torque, during isometric plantar flexion. The differences of the medial and lateral gastrocnemius pattern of decline implies that the two heads of the gastrocnemius muscle should be considered as separate entities. However, many factors not controlled for in this study, may have impacted the results. Therefore, health professionals should look at this study as a preliminary study in the investigation of the activation of the medial and lateral gastrocnemius muscles, leading to further investigation.
Abstract: The examination of moment and electromyographic (EMG) activity-angle curves of the agonists and antagonists is important for the determination of the mechanisms responsible for moment production during maximal activation of knee extensors and flexors. The purpose of this study was the examination of agonist and antagonistic activity of knee extensors and flexors at different knee joint angles during isokinetic exercise. Twelve females performed maximum isometric, eccentric and concentric isokinetic efforts of knee extensors and flexors on a Biodex dynamometer. The isokinetic tests were performed at angular velocities of 30, 60, 90, 120 and 150° Is. The EMG activity of vastus…lateralis, rectus femoris, vastus medialis and hamstrings was also recorded. The knee extensor and flexor maximal activity was found at angles ranging from 50° to 70° and from 20° to 40°, respectively. The antagonist activity was greater at the initial and final stages of the movement. Three way analysis of variance designs indicated significant differences in the agonist and antagonistic activity of knee extensors and flexors between eccentric and concentric exercise. The results of this study demonstrate that, despite changes in magnitude, the moment-angle and IEMG activity-angle patterns of the agonists were not affected by angular velocity and muscle action conditions. On the contrary, the IEMG activity-angle curves of the antagonists during maximal isokinetic voluntary efforts are affected by angular velocity conditions but were independent of the type of muscle action examined.
Abstract: We study the influence of the calculation of the trunk gravity correction, in standing position, on the isokinetic trunk flexors and extensors performance of a healthy population. Thirty men and 30 women are subjected to two tests, one with gravity correction, the other without, at angular speeds of 30°/s and 120°/s. In all cases, the results with gravity correction show: a significant decrease of Peak Torque (PT) and Power (P) recorded on the trunk flexors and a significant increase of Peak Torque and Power recorded on the trunk extensors. Thus, the flexors/extensors ratios (50%) of both parameters are quite different…from the ratios usually referred to in the literature (70%).
Abstract: The purpose of this study was to investigate the concentric and eccentric peak torque reliability of the Biodex B-2000, Kinetic Communicator, and Lido isokinetic dynamometers when testing the shoulder internal and external rotators. The subjects were 22 males with no previous shoulder pathology. Each subject completed two test sessions for each isokinetic dynamometer. The right upper extremity was tested at 120°/s through a 140° arc of motion with the shoulder in 90° of abduction. After a warm-up of three sub-maximal repetitions and 1 maximal repetition, five maximal repetitions were completed in either the concentric or eccentric mode. A 5-min rest…period lapsed and then the second test mode was completed. Six days later, the subjects were tested in the reverse order. This procedure was completed for each isokinetic dynamometer. Four one-way analyses of variance with repeated measures were used to compare peak torque values of shoulder internal and external rotation in each test mode. The F-values indicated significant differences in concentric and eccentric internal rotation and eccentric external rotation. Therefore indicating that comparisons of peak torque values should not be made between different isokinetic dynamometers. Means, standard error of measurement (SEM), and intraclass correlations (ICC) were calculated for each dynamometer in each test mode. The ICCs for concentric peak torque were generally higher than those of eccentric peak torque, but lower than those reported by previous researchers. Of the many variables that can impact isokinetic testing, position may have been the most influential in this study. It is possible that impingement of the shoulder rotators occured with the shoulder in 90 of abduction. Perhaps another test position would have yielded more consistent results. The presence of delayed onset muscle soreness may have also influenced this study. Copyright
Abstract: The purposes of this study were to determine the effects of unilateral leg extension concentric isokinetic resistance (CIR) training on: (1) hypertrophy at the largest anatomical cross-section of the vastus intermedius, vastus lateralis, vastus medialis, and rectus femoris muscles in the trained and untrained limbs and (2) strength of the quadriceps femoris muscle group in the trained and untrained limbs. Sixteen untrained young adult males [mean age 24.7 ± 5.1 (SD) years] volunteered to serve as subjects. The subjects were divided into two groups: (1) training group (TG, n = 8) and (2) control group (CG, n = 8). The…TG performed six sets of ten repetitions of extension of the non-dominant leg at 120°/s three times per week for 8 weeks on a Cybex II isokinetic dynamometer. The CG did not train. Pretraining and post-training leg extension peak torque at 120°/s and the largest anatomical cross-section of each muscle of the quadriceps femoris were determined utilizing a Cybex II dynamometer and magnetic resonance imaging scanner, respectively. The results indicated a significant (P < 0.05) increase (4.6%) in the CSA of the muscles of the non-dominant (trained) quadriceps femoris as well as significant (P < 0.05) increases in both non-dominant (trained) and dominant (untrained) quadriceps femoris strength (17.7 and 9.3%, respectively). There was no hypertrophy of the muscles of the dominant (untrained) limb. These data indicated that leg extension CIR training resulted in significant increases in both CSA and strength of the non-dominant (trained) quadriceps femoris as well as a significant increase in the strength, that was not accompanied by muscular hypertrophy, of the dominant (untrained) limb.
Keywords: Anatomical cross-section, Cross-training, Magnetic resonance imaging, Concentric, Isokinetic
Abstract: The purpose of this study was to compare lower extremity strength using a traditional isokinetic single joint (open kinetic chain) knee extension/flexion test and a multiple joint (closed chain) isokinetic leg press test in patients following an anterior cruciate ligament (ACL) reconstruction. Twenty three subjects underwent both isokinetic single and multiple joint testing at 180, 240, and 300°/s using a calibrated Biodex dynamometer. Testing was performed following (x = 15) weeks of accelerated knee rehabilitation with a predominantly closed chain rehabilitation protocol. Peak torque (PT) and single repetition work (SRW) were analyzed and compared bilaterally in both the single and…multiple joint tests. Single joint isokinetic knee extension testing measured strength of the injured limb relative to the uninjured limb at 74–77% for (PT) with multiple joint isokinetic extension testing at 91–93% for (PT). Significant (P < 0.001) differences were identified between the bilateral comparisons measured in the single and multiple joint isokinetic testing conditions for both PT and SRW. Results from this study demonstrate significant differences between single and multiple joint isokinetic testing in the lower extremity. This information is of vital importance to clinicians interpreting results of muscle function in patients following ACL reconstruction.
Keywords: Single versus multiple joint testing, ACL reconstruction, Isokinetics
Abstract: The purpose of this discussion is to review the methods utilized to calculate the intraclass correlation coefficient (ICC) as well as indications on the interpretation and application of the statistic in the assessment of reliability. The index result of the ICC and several examples of clinical and research applications of the ICC are given with respect to the reliability of isokinetic testing.
Abstract: Aging is associated with decreases in strength and muscle mass. In addition, the ability to maintain balance decreases with age. Few studies have examined the relationship between isokinetic muscle performance and balance performance. It was the purpose of this study to determine if there is a relationship between muscle and balance performance, and to discover how this relationship is affected by age. Fifty-five healthy females were recruited from two different age groups, 28 females who were 18–30 years of age mean age = 22.9 years (± 3.4), height = 163.5 cm (± 6.5), weight = 64.8 kg (± 15.7) and…26 females who were > 60 years of age mean age = 68.1 years (± 4.8), height = 159.7 cm (± 10.0), weight = 68.0 kg (± 11.4). Concentric and eccentric isokinetic muscle performance for the hip, knee, and ankle was measured using the KinCom isokinetic dynamometer. Balance performance was measured using the sharpened Romberg and one-legged stance tests. Younger subjects performed significantly better than older subjects on all muscle and balance performance variables (P = 0.05 to P = 0.0001), except the sharpened Romberg test with the eyes open. The older group exhibited significant relationships between balance and muscle performance measures (r = - 0.10 to r = 0.57). In the older group, hip muscle performance was shown to correlate significantly better with balance performance than knee or ankle muscle performance. Also noted was a significantly greater relationship between muscle performance and balance performance with the eyes closed in the older group, as compared to the younger group. This is the first study known to thoroughly examine the relationship between muscle and balance performance. The presence of significant relationships warrants further examination. It is recommended that this relationship be examined in a broad spectrum of young, old, healthy and disabled populations.
Abstract: Patellofemoral pain syndrome is a prevalent ailment experienced by a number of individuals participating in regular physical activity. Little information is available concerning the effects of patellofemoral bracing on the function of the extensor mechanism in patellofemoral malalignment patients. The purpose of this study was to examine the effects of patellar bracing on the extensor mechanism in relation to isokinetic exercise. Sixteen subjects exhibiting patellofemoral pain symptoms were tested on an isokinetic dynamometer with and without a patellofemoral brace. The testing procedure involved three maximal concentric/eccentric quadriceps contractions at an angular velocity of 180°/s. Electromyographic (EMG) activity of the vastus…medialis obliqus (VMO) and the vastus lateralis (VL) were recorded during testing. Integrated EMG activity (IEMG) was analyzed by a three-way ANOVA with repeated measures (p < 0.05). The results indicated that the application of the patellar brace resulted in a significantly smaller IEMG signal than during the non-braced condition in both the VMO and VL during both concentric and eccentric contractions (P < 0.05). The IEMG signal of the VMO was found to be significantly greater than the VL regardless of test or brace condition (P < 0.05). Moreover, the IEMG signal was also found to be significantly greater during the concentric contractions than the eccentric contractions during all testing conditions (P < 0.05). The clinical implication from this study suggests that muscle activation of the VMO and VL were reduced with the use of the brace. This type of bracing may provide mechanical support to the patellofemoral joint as evidenced by the reduction in quadriceps activation during isokinetic knee extension exercise.
Abstract: The purpose of this study was two-fold: (a) to further examine the efficiency of a novel protocol for differentiating maximal from submaximal effort of the knee extensors; and (b) to test the effect of effort performance order: maximal-submaximal vs. submaximal-maximal on the outcome, namely analyze an aspect of internal validity of the protocol. Thirteen women and 17 men took part in the study. They were randomly assigned to one of two groups. Group 1 performed a set of four intermittent maximal (MAX) concentric-eccentric contractions at 30 and 180°/s which was followed by an identical set but at a submaximal level.…In the latter set, subjects were asked to exert a submaximal level of force they could best reproduce (BREP). Group 2 performed the same sets but in a reverse order. Results have indicated: (1) no significant differences between the groups, hence prior exposure to maximal effort did not affect the differentiating capacity of the protocol; (2) no significant differences between absolute variability of the MAX and BREP conditions; (3) the DEC parameter defined as the difference in the eccentric/concentric force ratios at the high and low test velocities was highly effective (P < 0.001) in differentiating the MAX from the BREP conditions.