Isokinetics and Exercise Science - Volume 6, issue 1
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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: This investigation was designed to determine the test-retest reliability of a functional one legged hop test for distance in individuals with and without anterior cruciate ligament (ACL) reconstruction. Twenty subjects (X = 20.85 years) with no prior history of lower extremity injury, and 13 subjects (X = 22.40 years) with ACL reconstruction participated in this study. Testing occurred on two separate days with at least 24 h between testing sessions. The subjects executed a protocol consisting of a 5-min warm-up on a stationary bike, followed by three separate trial hops. This was followed by three separate hops which were measured…and recorded. The distance travelled for each hop was measured using a standard measuring tape. The same protocol was then repeated on the contralateral limb. The leg tested first was randomized with each subject. The subjects were then asked to return on the second day, wearing the same pair of athletic shoes, and repeat the identical protocol. The mean of the three hops were used in data analysis. Paired t-tests revealed no significant difference between the dominant and non-dominant legs on either pre-test or post-test in subjects with healthy knees. A significant difference was found when comparing involved to uninvolved limb on both the pre-test and post-test in patients with ACL reconstruction. There was no significant difference found from pre-test to post-test on either the dominant or non-dominant legs in healthy subjects or from the involved to uninvolved in patients with ACL reconstruction. Interclass correlation coefficients (ICC) revealed values of 0.92 and 0.96 for dominant and non-dominant legs, respectively. For individuals with ACL reconstruction, ICC values were 0.89 for both the involved and uninvolved limb. The results of this study suggest that the one legged hop test for distance is a reliable test for both young adults with healthy knees and those who have had ACL reconstruction. This test, along with others, may aid clinicians in determining whether patients are ready to return to prior level of activity.
Keywords: Functional tests, ACL reconstruction, One-legged hop test
Abstract: We evaluated three methods of strengthening the muscles of the lower leg in patients who had surgical reconstruction of the anterior cruciate ligament using an autogenous graft. Thirty-one patients met the study criteria of having a 15% or greater mean torque deficit in a muscle group of the involved leg compared with the same muscle group in the uninvolved leg, when tested on the Musculoskeletal Evaluation Rehabilitation and Conditioning System (MERAC, Universal Corporation, Cedar Rapids, Iowa). Patients were divided into three groups: open-kinetic chain MERAC, closed-kinetic chain Fitnet (Universal Corporation, Cedar Rapids, Iowa) leg press, and functional exercise. Functional testing,…open kinetic chain isokinetic testing and closed kinetic chain isokinetic testing were performed on all three groups pre- and post-training. A significant improvement in performance was found for all the groups over time on the MERAC, the Fitnet, and the functional tests. These results indicate that strengthening the muscles of the lower leg and improving function may be less dependent on the type of kinetic chain exercise, than on the muscle groups that are trained. The accommodating preset resistance and no restriction on the speed of movement during the exercise also may playa significant role in the development of strength and function.
Abstract: Elite level tennis players have shown a high incidence of lower back injuries. The objective of this study was to generate a descriptive profile of trunk extension and flexion strength as well as to examine the relationship between trunk strength and several field tests of physical fitness in elite junior tennis players. Measurements were obtained on 60 nationally ranked junior tennis players between 13 and 17 years of age. Trunk flexion and extension data were obtained concentrically on a Cybex 6000 Isokinetic dynamometer with TEF modular component at speeds of 60° s−1 and 120° s−1 . Peak torque/body weight…and work/bodyweight ratios were statistically analyzed in comparison to the field tests. A descriptive profile of isokinetic flexion/extension ratios was generated for elite junior tennis players. Trunk flexion/extension ratios ranged from 102 to 122% for peak torque at 60° s−1 and 120° s−1 . The field tests consisted of a standardized fitness testing protocol which included measurements of strength, power, speed and agility, endurance and flexibility. The correlated measurements included the total distance thrown on a forehand, backhand, overhead, and reverse overhead medicine ball toss. The analyses yielded significant correlations (range 0.47–0.82) between all isokinetic trunk flexion/extension data and the series of four medicine ball tosses, which were used in the field as a measurement of power (P < 0.01). These results demonstrate the relationship between isokinetic trunk testing and functional movement patterns. In addition, the isokinetic testing results provide an initial profile of trunk flexion and extension strength in elite junior tennis players.
Abstract: The purpose of this study was to investigate co-activation of the quadriceps and hamstring musculature during concentric and eccentric isokinetic actions at 30° s−1 . Eight female sedentary subjects performed maximal concentric and eccentric knee flexion/extension actions on an isokinetic dynamometer while simultaneous recordings of moment, joint position and agonist/antagonist electromyographic (EMG) activity from the rectus femoris and semitendinosus muscles were computer processed. Mean integrated electromyographic (IEMG) activity for agonist and antagonist muscle groups and mean moment data were calculated for three discrete knee angle ranges; outer (25–34°), mid (45–54°) and inner (65–74°) for both concentric and eccentric actions. Individual…IEMG activity was corrected to account for background activity in the unstressed muscle at 30°, 50° and 70° of knee flexion/extension. The results of this study show that under concentric and eccentric actions the hamstrings were more active during knee extension than the quadriceps were during knee flexion at all angle ranges studied. The corrected mean per cent IEMG activity of the co-contracting hamstrings throughout the joint range were 14 and 21% for concentric and eccentric actions respectively, for co-contracting quadriceps these values were 2.5 and 3.5% respectively. All per cent IEMG values were expressed as a percentage of the same muscle group and action (shortening/lengthening) during agonist action. No significant difference was seen between concentric and eccentric co-contraction per cent IEMG activity at any knee angle range studied. The data suggests that the hamstrings are used to a much greater extent than the quadriceps for limb deceleration and that in particular, hamstring antagonist muscle tension should be considered when analysing agonist quadriceps isokinetic moment curves.
Abstract: This study examined the effect of previous contraction condition on subsequent eccentric power production in the elbow flexor muscles in 20 healthy volunteers (10 males, 10 females). Power production was determined during constant velocity eccentric loading at 60°/s when preceded by: condition 1 passive elbow flexion; condition 2 maximal concentric contraction of the elbow flexor muscles; or condition 3 maximal isometric contraction of the elbow flexors. Comparison of eccentric power production under the different conditions was conducted using a repeated measures ANOVA. Results indicated that a continuum exists between conditions such that eccentric power production when preceded by condition 1…is < power production when preceded by condition 2, is < power production when preceded by condition 3. Implications are that contraction condition previous to eccentric loading allows various levels of tension transfer in the series elastic and the contractile components producing different levels of torque during the ensuing eccentric loading of the muscle. Techniques utilizing combinations of movement to enhancing muscle contraction should be examined critically with regard to order of movement and contraction conditions.
Abstract: The goal of the paper is to outline the topography of the strength of major muscle groups and to investigate the flexion:extension ratios in the joints of upper and lower extremities. There are number of papers undertaking different aspects of muscle strength — particularly concerning elbow flexors and knee extensors but there is only limited investigation on a sufficient number of muscle groups of one population, which would make it possible to outline the strength topography. For this purpose, the measurement of static torque of the flexors and extensors of elbow, shoulder, knee and hip joints was carried out. Twenty-two…students not practising sport were tested on a Merac machine. Some data of other authors on children and athletes is included for comparison. The relationship between the strength of muscle groups and body mass turned up to be non-linear. The similarities of the strength profile of the student group as compared with selected data of children and athletes are discussed. The flexion:extension ratios in some joints are quite different between groups, which is possibly — among other factors — due to different procedures applied.
Keywords: Strength profile, Major muscle groups, Flexion:extension ratios
Abstract: The BTE Dynatrac is an isotonic dynamometer in where the preset resistance determines the effort and the limb must overcome the resistance to accelerate through the ROM. Previous reliability studies of isokinetic devices do not apply to this type of dynamometer. Therefore, the purpose of this study was to assess the reliability of the BTE Dynatrac Isotonic Dynamometer using average work and power to determine whether the Dynatrac can produce consistent results under different preset loads and between exercise sessions. Twenty-nine (M = 19; F = 10) recreationally active college students underwent identical testing on three occasions. On a day…before testing, peak torque was measured from a 6 s maximal voluntary isometric contraction (MVIC) at 70° of knee flexion. This value determined the preset loads used for the three isotonic testing sessions. During the isotonic sessions each subject performed six repetitions of maximal knee extensions at preset loads (20%, 40%, and 60% of MVIC) through the 90° ROM. The order of testing on each of the three nonconsecutive days was determined by using a balanced Latin Square. Average work and power were recorded and analyzed. The reliability of average power measurement was excellent regardless of the preset load (20% MVIC = 0.82; 40% MVIC = 0.83; and 60% MVIC = 0.90). The reliability of average work measurement was excellent at 60% MVIC(0.86) and 40% MVIC(0.80), but only fair at 20% MVIC(0.57). We conclude that clinicians can be confident in comparing average power measurements between sessions regardless of the preset load and for average work at the moderate to higher preset loads.
Keywords: Isotonic, Muscle contraction, Reliability, Muscle power
Abstract: Plyometric training incorporates quick powerful movements involving an active pre-stretching (eccentric muscle contraction) prior to concentric contraction. It has been claimed that the effect of plyometric training could be enhanced using a frontal shoe orthotic due to increased overload created by this appliance. However, no study to date has examined this claim. Therefore, the purpose of the present study was to determine whether the use of the Jumpsole, a frontal shoe orthotic, will enhance the effect of plyometric training on vertical jump, 40 yard dash time, and calf circumference. Thirty five healthy eighth and ninth grade males participating on the…same junior high school football team volunteered to participate in this study. A stratified sampling technique was used to ensure similarity on a weight and position basis between a control group (18 males) and experimental group (17 males). The control group completed the 6-week training program without the Jumpsole shoe orthotic. The 6-week training program consisted of 45 min to 1 h sessions performed bi-weekly utilizing acceleration activity, skipping, lateral cone hops, bounding, jump rope, and depth (box) jumps. Vertical jump, 40 yard dash time, and calf circumference were measured before and after the 6 weeks of training. A two-way multivariate analysis of variance with repeated measures on one factor and appropriate follow-up repeated measures univariate analyses revealed that the only significant difference occurred between the pre-test and post-test (irrespective of influence of whether the subjects were in the experimental group or the control group) for the dependent variable vertical jump. These results indicate that, although the plyometric training program was effective for enhancing vertical jump, the training program did not improve speed of running or size of calf muscle. Additionally, the use of the frontal shoe orthotic in an attempt to enhance the plyometric training program was not effective.
Keywords: Frontal shoe orthotics, Plyometric training, Functional measurements, Junior high school football players
Abstract: The measurement of muscular strength of the shoulder internal and external rotators is an integral part of the comprehensive evaluation and treatment of the shoulder joint. The purpose of this study was to compare normal grade (5/5) manual muscle strength with isokinetic testing of the shoulder internal and external rotators. One hundred and fourteen consecutive subjects were tested isokinetically in the supine position with 90° of glenohumeral joint abduction on a Cybex 3S0 dynamometer. Prior to isokinetic testing each patient was tested by two physical therapists using manual muscle testing (MMT) with the shoulder abducted 90° for internal OR) and…external (ER) rotation. All subjects were rated as normal (5/5) grade for both IR and ER by both therapists to be included in this investigation. A two factor analysis of variance was used to test for differences between extremities. Results of this study showed significant (P < 0.01) differences between extremities in isokinetic peak torque and single repetition work scores. Differences between extremities ranged from 11 to 28% among a sample with normal grade (MMT). The results of this study identify objective, isokinetically measured discrepancies in muscular strength in subjects rated as ‘normal’ in shoulder internal and external rotation strength. This study demonstrates the efficacy of isokinetic testing of the shoulder internal and external rotators in clinical rehabilitation and evaluation of the glenohumeral joint.
Abstract: The purposes of the present study were to compare knee flexion torques determined in three test positions: (1) sitting; (2) prone; and (3) standing. Twenty-one healthy males (mean age 23 ± 2 years) completed tests in all three positions on each of two occasions, using isolated concentric and eccentric muscle actions. All tests were completed at 60° /sec angular velocity, using an. isokinetic dynamometer, with the sitting and prone tests completed using the dynamometer chair/bed. A specially built standing/stabilization frame was constructed to test knee flexion in standing. Averaging scores over two occasions was required to achieve reliability coefficients (ICCs)…greater than 0.75 for all tests. Standing tests were characterized by the lowest ICCs and the largest measurement error. Repeated measures analysis of variance (three positions by two muscle actions) indicated that the sitting position produced higher torques than did the prone (P < 0.01) and standing positions (P < 0.01), and the standing position produced higher torques than did the prone position (P < 0.01). All 21 subjects identified the standing position as permitting the fewest accessory movements, and providing the greatest isolation of the knee flexion movement and the hamstring muscles. Standing scores should not be compared with those determined in sitting or prone positions. In situations where the clinician wishes to isolate the knee flexors, the standing position is practical and may be advantageous. Future research needs to determine if reliability for standing tests can be improved and to examine the strength-function relationship for all three positions for testing knee flexion strength.
Keywords: Knee flexion, Isokinetic, Muscle strength, Test position