Isokinetics and Exercise Science - Volume 4, issue 3
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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: The purpose of this study was to investigate the effects of fatigue on the hamstrings and quadriceps during concentric and eccentric actions at 60 and 150 deg/sec. The dominant leg of 12 subjects was tested on the Biodex B-2000 isokinetic dynamometer (Biodex Medical Systems, Shirley, NY). The results showed that the eccentric mode of action, 150 deg/sec angular velocity, and quadriceps muscle group were levels at which fatigue was significantly delayed than at corresponding levels of concentric mode of contraction, 60 deg/sec angular velocity, and hamstrings muscle group. Subsequent analysis showed a significant three-way interaction. A significant simple, main effect…was determined to exist for the quadriceps muscle group at the 150 deg/sec angular velocity for mode of action; concentric fatigue was significantly greater than eccentric fatigue. The findings of the present study suggest that isokinetic fatigue training protocols must be designed to meet the specific training objectives if the desired outcomes are to be met.
Keywords: Fatigue response, concentric and eccentric measures, velocity specificity
Abstract: The isokinetic strength and endurance of the trunk extensors and flexors in 72 normal male and female subjects were evaluated concentrically from 25° of extension to 30° of flexion at angular velocities of 20, 40, and 60 deg/sec, on two occasions. Full range of motion (ROM) average torque (FRAT) and truncated ROM average torque (TRAD were calculated. The direct values and derived ratios were analyzed by repeated-measures analysis of variance and Pearson product moment correlations. Direct FRAT and TRAT measures, although highly correlated (r > 0.997), were significantly different (p = 0.000) at each of the three angular velocities. Derived…agonist/antagonist ratios had slightly lower correlations (r > 0.980) and were significantly different from each other only at 40 and 60 deg/sec (p = 0.0001 and p = 0.0012). It was concluded that for measurements of isokinetic strength of TEs and TFs, the initial and terminal nonisokinetic phases should be truncated before calculating the average torque, unless the result is expressed as the agonist/antagonist ratio and the angular velocity of measurement is slow.
Keywords: Trunk extensor/flexor, trunk flexor/extensor, full range of motion average torque, truncated range of motion average torque
Abstract: Problems during the deceleration phase of running include muscle trauma and eccentric force deficits caused by a maladaptation within the nervous system. Eccentric muscle dysfunction should be greater in runners than in cyclists because cycling does not involve weight-bearing repetitive deceleration. Therefore, we compared the endurance of runners and cyclists for eccentric torque production across velocities to determine if the eccentric torque-velocity relationship of cyclists was different than that of runners. Ten endurance runners and 10 endurance cyclists were tested for isokinetic eccentric and concentric knee extension peak torque (PT) at 30, 90, 150, and 210 deg/sec (0.52, 1.57, 2.62,…and 3.66 rad/sec). The cyclists produced (p≤0.05) greater concentric and eccentric PT. Eccentric and concentric PT were different across velocities (p≤0.05), but the type of exercise by velocity interaction was not different (p≥0.05). In addition, a significant linear trend (p≤0.05) was noted across velocities for concentric PT for both runners and cyclists. Thus, as velocity increases, a significant decrease is seen in concentric PT. No increase or decrease in eccentric PT (p≥0.05) across the four velocities was observed in either runners or cyclists. We conclude that eccentric PT is greater than concentric PT and that eccentric PT does not change as velocity increases. Therefore, the type of exercise, whether highly decelerative or not, does not influence the shape of the eccentric torque-velocity relationship. The lack of change in eccentric PT with increasing velocity may be due to a neural mechanism that is activated during maximal contractions to help ensure a safe maximum tension level.
Abstract: Although gaining popularity in sports physical therapy, few data exist as to the reliability of functional tests for the lower extremity; neither has “normal” right-left symmetry been established. Therefore, the threefold purpose of this study was to (1) describe five common and relatively simple functional tests, (2) investigate the reliability of these tests, and (3) determine the differences in the ability of the right and left limb to perform these functional tests. Testing of these five functional tests was performed three times across a 3-week period using standardized procedures for four different samples, with each sample performing a different functional…test. Eighteen volunteers completed the one-legged horizontal hop test, 16 subjects participated in the one-legged vertical hop, and 18 subjects completed the timed one-legged hop test. One sample of 22 subjects participated in both the one-legged triple-hop test and the one-legged cross-over hop test. Results indicated right-left differences of all five functional tests to be less than 1% and reliability correlation coefficients ranged from 0.85 to 0.94. Given the reliability coefficients obtained and the absence of clinically important right-left differences, the data collected from this study suggest that functional tests have the potential to be a valuable adjunct in the assessment of the athlete after injury.
Abstract: This study compared the test results from two spinal isokinetic dynamometers, the Cybex TEF and the Cybex 6000-TMC (Cybex, Ronkonkoma, NY) in an effort to establish the measurement reliability of the latter device and to develop formulas for the interconversion of test results. A stratified random sample of 5,760 normal subjects (2,880 females, 2,880 males; mean age 25.0±9.9 years; age range 17–49 years) was tested on both devices under an alternate repeated-measures paradigm across the concentric isokinetic speeds of 30, 60, 90, and 120 deg/sec after standardized warmup procedures. Data for peak torque expressed as a percentage of body weight…was collected from five maximal repetitions of spinal flexion and extension at all test speeds and then subjected to multiple statistical analyses. Results showed a high level of measurement reliability for both the TEF (intraclass correlation [ICC] = 0.927) and the TMC (ICC = 0.910); failed to show significant differences in subject performances across devices, speeds, genders, and motions; and showed comparison formulas of TEF = TMC + 13.325, TEF = TMC + 15.225, TEF = TMC + 15.775, and TEF = TMC + 16.775 for female and male spinal flexion and extension, respectively. The results may be useful for the design of clinical programs that include spinal isokinetic testing procedures.
Abstract: The purposes of the study were to (1) identify ratios for the evertor and invertor muscles of the ankle and (2) determine whether gender differences existed in ankle strength ratios of healthy, young adults. Twelve females and 13 males consented to be tested bilaterally on a single occasion for ankle inversion and eversion at two velocities (30 and 120 deg/sec) using the Cybex 330 isokinetic dynamometer (Cybex, Ronkonkoma, NY). Two- and three-way analyses of variance and post-hoc Neuman-Keuls tests were used to analyze the data. Results indicated that the invertor muscles were stronger than the evertor muscles at all velocities…(26.31% at 30 deg/sec, 29.14% at 120 deg/sec), ankles tested (32.35% for the preferred, 22.23% for the nonpreferred), and genders (26.08% for males, 29.39% for females). With the exception of inversion at the slow velocity for the preferred ankle, there were no differences between the ankles for velocities or movements tested. Similar ratios of eversion/inversion strength were observed for each gender at either velocity. However, ratios differed significantly between the preferred (dominant) and nonpreferred (nondominant) ankles. It was concluded that individual ratios must be used to determine appropriate antagonistic strength ratios for the preferred and nonpreferred ankles (65% and 75%, respectively) and that no differences in gender effect were observed.
Abstract: The purpose of this study was to examine muscle performance output as effected by electrical stimulation with and without eledromyographic (EMG) biofeedback in conjunction with quadriceps femoris muscle (QFM) strengthening exercises. Six males and six females aged from 20 to 36 participated in this study. Subjects were assigned to one of three independent groups. One group (n = 4) performed maximal volitional isometric contractions (MVICs) of the QFM and served as the control; the second group (n = 4) underwent strength training augmentation concurrent with electrical stimulation; the third group (n = 4) received EMG biofeedback-triggered electrical stimulation (BTES), i.e.,…electrical stimulation based on EMG biofeedback from volitional isometric contractions. Each group underwent pretesting and posttesting to record MVICs. The groups trained 3 days a week for 6 weeks. All groups had an increase in peak torque production over the 6-week training period, with the EMG-BTES group showing the greatest increase from pretest to posttest. Results of this study give preliminary evidence of the usefulness of electrical stimulation, especially when triggered by an EMG biofeedback signal, in strength training.