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Frank E. Seagraves and Michael Horvat

The purpose of this investigation was to compare isometric test procedures (make vs. break tests by muscle groups) with elementary school girls, ages 9–11, using hand-held dynamometry. Fifty subjects in Grades 3 and 4 performed three trials on four muscle groups using each testing procedure following a preliminary session to allow familiarity with the instrumentation, test procedures, and test positions. Retest measurements were taken in 5–7 days with the order of the test procedures counterbalanced. Four 2 × 2 (Side × Test Condition) AM0VAs, with repeated measures on each-factor, were used to analyze the data. Significant Side × Test Condition interaction effects were evident for knee extension, elbow flexion, and shoulder abduction. Except for the knee extension, the break test produced higher values than the make test in all muscle groups, which is in agreement with previous investigations.

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Andrew C. Fry, Dawn R. Powell and William J. Kraemer

Although it is generally accepted that human performance must be assessed in a manner specific to the training, previous studies have violated this principle. In order to determine the validity of evaluating short-term resistance training programs with isometric and isokinetic measures, 23 recreationally active males participated in an 8-week training program. Subjects were randomly divided into barbell squat, hip sled, leg extension, and control groups. Pre- and posttesting of quadriceps strength was performed with a Cybex isokinetic dynamometer. Six angle-specific torques (N.m) were determined at 0 rad-s-1 and 1.05 rad-s-1. Ten RM training loads increased significantly for all groups that trained. Isometric torque values differed significantly from isokinetic torque values at 30, 60, 75, and 90° of leg flexion for all groups. No significant torque increases from pre- to posttest were observed for any group at any limb angle for either isometric or isokinetic testing, or for isokinetic peak torque. This indicates that strength increases during short-term dynamic external resistance exercise are not adequately assessed with either isometric or isokinetic evaluations.

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Ralf Roth, Lars Donath, Lukas Zahner and Oliver Faude

For performance and injury prevention in sport, core strength and endurance are focused prerequisites. Therefore we evaluated characteristics of trunk muscle activation and performance during strength-endurance related trunk field tests. Strength-endurance ability, as total time to failure, and activation of trunk muscles was measured in 39 football players of the highest German female football league (Bundesliga) (N = 18, age: 20.7 y [SD 4.4]) and the highest national male under-19 league (N = 21, age: 17.9 y [0.7]) in prone plank, side plank, and dorsal position. Maximal isometric force was assessed during trunk extension and flexion, rotation, and lateral flexion to normalize EMG and to compare with the results of strength-endurance tests. For all positions of endurance strength tests, a continuous increase in normalized EMG activation was observed (P < .001). Muscle activation of the rectus abdominis and external oblique in prone plank position exceeded the maximal voluntary isometric contraction activation, with a significantly higher activation in females (P = .02). We conclude, that in the applied strength-endurance testing, the activation of trunk muscles was high, especially in females. As high trunk muscle activation can infer fatigue, limb strength can limit performance in prone and side plank position, particularly during high trunk muscle activation.

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Roger O. Kollock Jr., Bonnie Van Lunen, Jennifer L. Linza and James A. Onate

Context:

Assessment of hip strength can be performed with either isokinetic or isometric testing procedures, but the degree of association between values derived from the alternative testing methods has not been previously documented.

Objective:

To investigate the relationship between isometric peak torque and isokinetic peak torque at 60°·s-1 for various hip motions.

Participants:

Eighteen physically active males (N = 9) and females (N = 9) participated (22 ± 3 years, 173.0 ± 10.5 cm, 73.8 ± 16.7 kg).

Intervention(s):

Three isokinetic repetitions at 60°·s-1 and three isometric contractions of 5 s each for the hip fexors (HFs), hip extensors (HEs), hip abductors (ABs), hip adductors (ADs), hip external rotators (ERs), and hip internal rotators (IRs).

Outcome Measures:

Pearson correlation coefficients and coefficients of determination were calculated for both absolute and allometric-scaled peak torque values.

Results:

Meaningful associations between isometric and isokinetic peak torque values were found for each hip motion. Allometric-scaled strength values demonstrated stronger correlations than absolute strength values.

Conclusions:

The results suggest that portable fixed isometric testing of hip strength is an alternative to isokinetic testing at 60°·s-1.

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Stefan C. Garcia, Jeffrey J. Dueweke and Christopher L. Mendias

Context: Manual isometric muscle testing is a common clinical technique used to assess muscle strength. To provide the most accurate data for the test, the muscle being assessed should be at a length in which it produces maximum force. However, there is tremendous variability in the recommended positions and joint angles used to conduct these tests, with few apparent objective data used to position the joint such that muscle-force production is greatest. Objective: To use validated anatomically and biomechanically based musculoskeletal models to identify the optimal joint positions in which to perform manual isometric testing. Design: In silico analysis. Main outcome measure: The joint position which produces maximum muscle force for 49 major limb and trunk muscles. Results: The optimal joint position for performing a manual isometric test was determined. Conclusion: Using objective anatomical models that take into account the force-length properties of muscles, the authors identified joint positions in which net muscle-force production was predicted to be maximal. This data can help health care providers to better assess muscle function when manual isometric strength tests are performed.

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Aron J. Murphy, Greg J. Wilson, John F. Pryor and Robert U. Newton

The purpose of this investigation was to determine the relationship between isometric measures of muscular function at two different joint angles and dynamic performance. Thirteen experienced weight trainers performed two isometric tests in a bench press position, at elbow angles of 90 and 120°. Performance was assessed by a one repetition maximum (1-RM) bench press and a series of upper body bench press throws at loads of 15, 30, and 60% of the 1-RM load. The results clearly show that changing the joint angle from 120 to 90° improved the relationship between most of the tests and performance by more than 100%, possibly due to differences in motor unit recruitment patterns and differing muscle mechanics (e.g., length-tension), at varying joint angles. It was suggested that the best angle at which to assess isometric function may be the joint angle at which peak force is developed in the performance of interest.

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Theodoros Kannas, Eleftherios Kellis, Fotini Arampatzi and Eduardo Saez Saez de Villarreal

The aim of this study was to examine the differences in muscle architecture during isometric tests between children and adults. Eight boys (age= 11.2 ± 0.26 years) and eight men (age= 22.3 ± 2.01 years) performed plantar flexion isometric efforts at angles of -15°, 0°, 15° at 0%, 40%, 60%, 80% of MVC. Analysis of variance tests indicated that adults showed greater fascicle length from rest to 80% of MVC (p < .05), greater pennation angle at 80% and 100% of MVC (p < .05) and greater aponeuroses displacement at levels of effort greater than 60% of MVC (p < .05). These differences observed in MG would appear to favor better utilization of the force-length and the force-velocity relationships, of the muscle in adults compared with children.

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J. Allen Hardin, John A. Guido and Christopher J. Hughes

Due to the likelihood of hamstring dysfunction associated with anterior cruciate ligament (ACL) injury, it is clinically significant to determine if a hamstring weakness exists preoperatively. The purpose of this study was to determine if a hamstring muscle deficit existed at the time of surgery and to determine the time necessary to achieve hamstring strength equal to preoperative measures of the uninvolved extremity during postoperative rehabilitation. Twelve patients who underwent ACL reconstruction using a patellar tendon autograft participated. Each subject underwent a preoperative isometric knee strength evaluation at 60° of knee flexion. Each subject underwent postoperative rehabilitation including hamstring muscle strengthening. Repeat isometric testing was performed on each subject at 21 and 42 days postoperative. There was no statistical difference in hamstring muscle strength, as measured by isometric peak torque, either preoperatively or postoperatively. Therefore, maintaining rather than increasing hamstring strength postoperatively should be emphasized as an integral part of rehabilitation.

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Antonio Dello Iacono, Stephanie Valentin, Mark Sanderson and Israel Halperin

. Both are valid and reliable, 2 , 3 correlated with performance indices, 4 , 5 can distinguish between level of athletes, 6 , 7 and easy to administer and time efficient. 1 These isometric tests are extensively studied and implemented. However, both have 2 limitations. First, they require a force

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Claire J. Brady, Andrew J. Harrison, Eamonn P. Flanagan, G. Gregory Haff and Thomas M. Comyns

following a 48-hour rest. The sequence of the isometric tests was randomized among the subjects to limit possible effects of potentiation and fatigue. Subjects had a 5-minute rest between the 2 isometric tests. Subjects completed a general warm-up consisting of 3 minutes of cycling, 10 bodyweight squats, 10