Influence of pulsed modes of a magnetic field on an electric vortex flow

Using a fiber-optic velocity transducer, the effect of external pulsed magnetic fields on the structure of electrovortex flows is experimentally investigated. It is shown that an external pulsed magnetic field can lead to the appearance of oscillations of significant amplitude in a liquid metal.

Reliability and concurrent validity of the PUSH Band™ 2.0 to measure barbell velocity during the free-weight and Smith machine squat exercises

The aim of this study was to examine the test-retest reliability and concurrent validity of the PUSH Band™ 2.0 to measure barbell’s velocity during unconstrained (free-weights) and constrained (Smith machine) squat exercises. After an initial assessment of the Smith machine squat one-repetition maximum (1RM), 24 resistance-trained males completed one or two testing sessions separated by 7 days. In one session, the squat was performed with free-weights ( n = 22), while in another session, the Smith machine was used ( n = 16). Both testing sessions consisted of two blocks of eight repetitions (three repetitions at 45%1RM, three repetitions at 65%1RM, and two repetitions at 85%1RM). The mean velocity of the lifting phase was simultaneously recorded with the PUSH Band™ 2.0 and a gold-standard linear velocity transducer (T-Force® System). The PUSH Band™ 2.0 generally revealed an acceptable reliability (CVrange = 5.81%–13.14%), but the reliability was always greater for the T-Force® System (CVrange = 2.95%–7.86%). Regardless of the squat exercise, the concurrent validity of the PUSH Band™ 2.0 with respect to the T-Force® System was generally low at 45%1RM (ESrange = 0.18–0.33; rrange = 0.58–0.75; SEErange = 0.04–0.05 ms−1 and 4.2%–6.0%), 65%1RM (ESrange = 0.26–0.44; rrange = 0.63–0.82; SEErange = 0.04–0.06 ms−1 and 6.0%–9.2%), and 85%1RM (ESrange = 0.61–0.64; rrange = 0.66–0.82; SEErange = 0.05–0.07 ms−1 and 11.4%–16.0%). Taken together, these results suggest that the PUSH Band™ 2.0 is a reliable, but not valid, wearable technology to measure the barbell velocity during the free-weight and Smith machine squat exercises.

Sensitivity of the iLOAD® Application for Monitoring Changes in Barbell Velocity Following Power- and Strength-Oriented Resistance Training Programs

Objective: To evaluate the sensitivity of the iLOAD® application to detect the changes in mean barbell velocity of complete sets following power- and strength-oriented resistance training (RT) programs. Methods: Twenty men were randomly assigned to a power training group (countermovement jump and bench press throw at 40% of the 1-repetition maximum [1RM]) or strength training group (back squat and bench press at 70% to 90% of 1RM). Single sets of 10 repetitions at 25% and 70% of 1RM during the back squat and bench press exercises were assessed before and after the 4-week RT programs simultaneously with the iLOAD® application and a linear velocity transducer. Results: The power training group showed a greater increment in velocity performance at the 25% of 1RM (effect size range = 0.66–1.53) and the 70% of 1RM (effect size range = 0.11–0.30). The percent change in mean velocity after the RT programs highly correlated between the iLOAD® application and the linear velocity transducer for the back squat (r range = .85–.88) and bench press (r range = .87–.93). However, the iLOAD® application revealed a 2% greater increase in mean velocity after training compared to the linear velocity transducer. Conclusions: The iLOAD® application is a cost-effective, portable, and easy-to-use tool which can be used to detect changes in mean barbell velocity after power- and strength-oriented RT programs.

Force-Velocity Relationship in the Countermovement Jump Exercise Assessed by Different Measurement Methods

This study aimed to compare force, velocity, and power output collected under different loads, as well as the force-velocity (F-V) relationship between three measurement methods. Thirteen male judokas were tested under four loading conditions (20, 40, 60, and 80 kg) in the countermovement jump (CMJ) exercise, while mechanical output data were collected by three measurement methods: the Samozino's method (SAM), a force platform (FP), and a linear velocity transducer (LVT). The variables of the linear F-V relationship (maximum force [F0], maximum velocity [V0], F-V slope, and maximum power [P0]) were determined. The results revealed that (1) the LVT overestimated the mechanical output as compared to the SAM and FP methods, especially under light loading conditions, (2) the SAM provided the lowest magnitude for all mechanical output, (3) the F-V relationships were highly linear either for the SAM (r = 0.99), FP (r = 0.97), and LVT (r = 0.96) methods, (4) the F-V slope obtained by the LVT differed with respect to the other methods due to a larger V0 (5.28 ± 1.48 m·s-1) compared to the SAM (2.98 ± 0.64 m·s-1) and FP (3.06 ± 0.42 m·s-1), and (5) the methods were significantly correlated for F0 and P0, but not for V0 or F-V slope. These results only support the accuracy of the SAM and FP to determine the F-V relationship during the CMJ exercise. The very large correlations of the SAM and LVT methods with respect to the FP (presumed gold-standard) for the mean values of force, velocity and power support their concurrent validity for the assessment of mechanical output under individual loads.

Investigation of the Characteristics of the Three-axis Ring Typed Angular Velocity Transducer Based on Optical Tunneling Effect

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