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

a lack of studies that include representative samples of high-level sprinters performing isometric strength tests that assess various strength qualities to help identify the best correlations with speed performance. This information could assist coaches in choosing appropriate tests for use in

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Megan Q. Beard, Samantha A. Boland and Phillip A. Gribble

, transportable, and more economical. Although the HHD can be effective, the reliability of the device can be influenced by examiner experience, patient position, and the use of stability straps. Previous studies have determined isometric strength testing using a HHD can have high interexaminer reliability and

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Heiner Baur, Alessia Severina Groppa, Regula Limacher and Lorenz Radlinger

Maximum strength and rate of force development (RFD) are 2 important strength characteristics for everyday tasks and athletic performance. Measurements of both parameters must be reliable. Expensive isokinetic devices with isometric modes are often used. The possibility of cost-effective measurements in a practical setting would facilitate quality control. The purpose of this study was to assess the reliability of measurements of maximum isometric strength (Fmax) and RFD on a conventional leg press. Sixteen subjects (23 ± 2 y, 1.68 ± 0.05 m, 59 ± 5 kg) were tested twice within 1 session. After warm-up, subjects performed 2 times 5 trials eliciting maximum voluntary isometric contractions on an instrumented leg press (1- and 2-legged randomized). Fmax (N) and RFD (N/s) were extracted from force-time curves. Reliability was determined for Fmax and RFD by calculating the intraclass correlation coefficient (ICC), the rest-retest variability (TRV), and the bias and limits of agreement. Reliability measures revealed good to excellent ICCs of .80-.93. TRV showed mean differences between measurement sessions of 0.4-6.9%. The systematic error was low compared with the absolute mean values (Fmax 5-6%, RFD 1-4%). The implementation of a force transducer into a conventional leg press provides a viable procedure to assess Fmax and RFD. Both performance parameters can be assessed with good to excellent reliability allowing quality control of interventions.

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Richard L. Urbanski, Steven F. Loy, William J. Vincent and Ben B. Yaspelkis III

Ten physically active, untrained, college-aged males (26.4 ± 5.8 years old) received creatine (CR. 5 g creatine monohydrate + 3 g dextrose) and placebo (PLA, 7 g dextrose) supplementation four times per day for 5 days in a double-blind, randomized, balanced, crossover design. Performance was assessed during maximal and three repeated submaximal bouts of isometric knee extension and handgrip exercise. CR supplementation significantly increased (p < .05) maximal isometric strength during knee extension but not during handgrip exercise. CR supplementation increased time to fatigue during each of the three bouts of submaximal knee extension and handgrip exercise when compared to the PLA trials. These findings suggest that CR supplementation can increase maximal strength and lime to fatigue during isometric exercise. However, the improvements in maximal isometric strength following CR supplementation appear to be restricted to movements performed with a large muscle mass.

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Samuel R. Heaselgrave, Joe Blacker, Benoit Smeuninx, James McKendry and Leigh Breen

isometric strength were measured before and after 6 weeks of RT with 9, 18, or 27 weekly sets in RT-experienced males. We hypothesized that RT-induced changes in muscle mass and strength would be greater in response to 18 versus 9 weekly sets (performed over 2 and 1 weekly session[s], respectively), but

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Ryan T. Tierney

Column-editor : Carl G. Mattacola

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Johanne Desrosiers, François Prince, Annie Rochette and Michel Raîche

The objectives of this study were to standardize measurement procedures and study the test-retest and interrater reliability of the belt-resisted method for measuring the lower extremity isometric strength of three muscle groups. The strength of 33 healthy, elderly, community-dwelling subjects was evaluated with a hand-held dynamometer using the belt-resisted method. Isometric strength testing of three muscle groups (hip flexors, knee extensors, and ankle dorsiflexors) was performed on two separate occasions, I week apart, by the same tester to determine test-retest reliability. The test results of two different examiners testing on different days were used to determine interrater reliability. Test-retest reliability was higher than interrater reliability. Test-retest reliability coefficients of the three muscle groups were high (J9-.95). For interrater reliability, intraclass correlation coefficients varied from .64 to .92. depending on the muscle group and side. For the two kinds of reliability, intraclass correlation coefficients increased from proximal to distal. The method for the hip muscle group should be modified to increase reliability of the measure.

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

.1_6 15. Thomas C , Jones PA , Rothwell J , Chiang CY , Comfort P . An investigation into the relationship between maximum isometric strength and vertical jump performance . J Strength Cond Res . 2015 ; 29 ( 8 ): 2176 – 2185 . PubMed ID: 25647649 doi:10.1519/JSC.0000000000000866 25647649

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Jenny Toonstra and Carl G. Mattacola

Context: Physicians and clinicians need portable, efficient, and cost-effective assessment tools to determine the effectiveness of rehabilitation programs after knee injury. Progress in rehabilitation should be evaluated using valid and reliable measurement methods. Objective: To examine the test-retest reliability of portable fixed dynamometry (PFD), handheld dynamometry (HHD), and isokinetic dynamometry (IKD). In addition, the authors sought to examine the validity of PFD and HHD by comparing differences in peak torque of the knee flexors and extensors to that of the "gold standard" IKD. Design: Repeated measures. Participants: 16 healthy subjects (age 29.3 ± 7.2 y, height 167.4 ± 8.04 cm, mass 73.7 ± 20.0 kg). Main Outcome Measures: The dependent variables were trial (trial 1, trial 2) and instrument (IKD, PFD, and HHD). Results: Test-retest reliability was high for both PFD and IKD. However, fair to poor reliability was found for HHD. There were no differences in peak torque (Nm) between IKD and PFD. However, significant differences in peak torque were observed between IKD and HHD and between PFD and HHD. Conclusions: PFD provides reliable measures of strength and also demonstrates similar output measures as IKD. Its portability, ease of use, and cost provide clinicians an effective means of measuring strength.

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Luke Van Wyk, Gwendolen Jull, Bill Vicenzino, Mathew Greaves and Shaun O’Leary

The purpose of this study was to compare maximal torque exerted about the craniocervical (CC) and cervicothoracic (CT) axes in the sagittal plane using a novel dynamometry device. Maximal voluntary contraction (MVC) recordings in newton-meters (N·m) were measured in 20 males and 20 females for each of 4 tests: CT extension, CT flexion, CC extension, CC flexion. Twenty of the volunteers repeated the testing procedure on a second occasion to determine the test–retest repeatability of the measures. MVC recordings at the CT axis (extension, 30.24 ± 12.15 N·m; flexion, 18.90 ± 8.21 N⋅m) were 1.4–2 times greater than recordings at the CC axis (extension, 16.46 ± 7.26 N⋅m; fexion, 13.34 ± 5.97 N·m). Extensor to flexor strength ratios reduced from 1.75 at the CT axis to 1.24 at the CC axis, but were similar for both males and females. Good to excellent test–retest repeatability was demonstrated for all tests (ICC = 0.75–0.99, SEM = 0.50–2.44 N·m). Consistent with differences in the muscle morphology at the CC and CT axes, torque exerted about these axes differ. Separate measurement of torque about these axes potentially offers a more comprehensive profile of cervical muscle strength.