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Effects of Multipath and Conventional NMES on Maximum Comfortable Stimulus and Torque Production

100%
Bremner C. B., Holcomb W. R.
Central European Journal of Sport Sciences and Medicine
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2019
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vol. 25
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issue 1
23-33
EN
A novel multipath NMES (m-NMES) device has shown improved outcomes relative to conventional NMES (c-NMES) during recent basic and training studies. However, the mechanisms by which m-NMES outperformed c-NMES remain unclear. This study aimed to better understand these mechanisms by comparing the effects of m-NMES and c-NMES on maximum comfortable stimulus intensity and the subsequent NMES-induced torque, as these variables ultimately impact NMES training intensity; which is considered to be the primary determinant of NMES effectiveness. We measured maximum comfortable stimulus intensity and the subsequent NMES-induced torque while participants performed NMES-induced contractions under two conditions (m-NMES and c-NMES). Maximum comfortable stimulus intensity was significantly greater under the m-NMES condition, but the subsequent NMES-induced torque was not significantly different across conditions. m-NMES does not appear to influence the outcomes in a clinically meaningful manner, since it performed similarly to c-NMES with respect to peak NMES-induced torque.
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Effects of High-Intensity Blood Flow Restriction Exercise on Muscle Fatigue

100%
Neto G. R., Santos H. H., Sousa J. B. C., Júnior A. T. A., Araújo J. P., Aniceto R. R., Sousa M. S. C.
Journal of Human Kinetics
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2014
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vol. 41
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issue 1
163-172
EN
Strength training combined with blood flow restriction (BFR) have been used to improve the levels of muscle adaptation. The aim of this paper was to investigate the acute effect of high intensity squats with and without blood flow restriction on muscular fatigue levels. Twelve athletes (aged 25.95 ± 0.84 years) were randomized into two groups: without Blood Flow Restriction (NFR, n = 6) and With Blood Flow Restriction (WFR, n = 6) that performed a series of free weight squats with 80% 1-RM until concentric failure. The strength of the quadriceps extensors was assessed in a maximum voluntary isometric contraction integrated to signals from the surface electromyogram. The average frequency showed significant reductions in the WFR group for the vastus lateralis and vastus medialis muscles, and intergroup only for the vastus medialis. In conclusion, a set of squats at high intensity with BFR could compromise muscle strength immediately after exercise, however, differences were not significant between groups.
3
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Effect of a Short Time Concentric Versus Eccentric Training Program on Electromyography Activity and Peak Torque of Quadriceps

88%
Carvalho A., Caserotti P., Carvalho C., Abade E., Sampaio J.
Journal of Human Kinetics
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2014
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vol. 41
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issue 1
5-13
EN
The purpose of this study was to examine the effect of an 8-week concentric (CON) versus eccentric (ECC) isokinetic training program on the electromyography (EMG) signal amplitude of vastus medialis (VM), vastus lateralis (VL) and rectus femoris (RF). Also, the isometric (ISO) and dynamic maximum strength of the knee extensors were assessed. Eighteen physically healthy male subjects (age 22 ± 1 years, body height 177 ± 4 cm, body mass 73 ± 7 kg) performed four weeks of unilateral CON isokinetic training for the quadriceps of the dominant leg on a REV9000 dynamometer. At the end of the fourth week, the sample was divided into two groups, with one group performing additional four weeks of unilateral ECC training and the other continuing with CON training. The training sessions consisted of three sets of ten maximal repetitions at a velocity of 60°s-1, three days per week for eight weeks. The results showed that CON and ECC groups improved the peak torque in all types of contractions. Also, both groups presented increases in the avgEMG for VL, VM and RF. The present investigation showed that CON training elicited increases of the ISO peak torque and VM avgEMG in the CON contraction. Additionally, significant gains were reported after the ECC training on the VM avgEMG in all contractions and RM avgEMG in CON contraction.
4
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Evaluation of Consecutive Maximum Contractions as a Test of Neuromuscular Function

75%
Suzovic D., Nedeljkovic A., Pazin N., Planic N., Jaric S.
Journal of Human Kinetics
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2008
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vol. 20
51-61
EN
The aim of the study was to conduct a preliminary evaluation of consecutive maximum contractions (CMC) as a test of neuromuscular function. Eleven participants performed externally paced isometric CMC (i.e., a series of consecutive maximum force exertions and relaxations) of the quadriceps muscle. The derived variables included the peak forces, and the maximum rates of force development and relaxation. The results revealed high within-day reliability of CMC variables, while their correlations with the jumping performance were consistently higher than those of the variables of the standard strength test (SST). CMC variables also showed fairly stable values across a wide range of frequencies, while their peak force revealed a strong relationship with maximum force of SST despite being about considerably lower. Therefore, we conclude that CMC could be developed into a standard test of neuromuscular function. In addition to capturing the muscle actions based on different neural activation pattern than SST, CMC could also be based on simpler testing procedure, lower force exertion, and self-selected frequencies.
5
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Reliability of Concentric, Eccentric and Isometric Knee Extension and Flexion when using the REV9000 Isokinetic Dynamometer

75%
Pereira de Carvalho Froufe Andrade A. C., Caserotti P., Pereira de Carvalho C. M., André de Azevedo Abade E., Jaime da Eira Sampaio A.
Journal of Human Kinetics
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2013
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vol. 37
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issue 1
47-53
EN
The aim of this study was to assess the reliability of isokinetic and ISO knee extensor and flexor muscle strength when using the REV9000 (Technogym) isokinetic dynamometer. Moreover, the reliability of several strength imbalance indices and bilateral ratios were also examined. Twenty-four physically active healthy subjects (age 23±3 years) underwent three testing sessions, two on the same day and a third, 7 days later. All sessions proceeded in the same order: five concentric contractions at 60ºs-1 followed by an isometric contraction (5 seconds) and five eccentric contractions (60ºs-1). The results of this study showed a high reproducibility in eccentric (0.95-0.97), concentric (0.95- 0.96) and isometric (0.93-0.96), isokinetic strength for knee extensor and flexor muscles, thus indicating that the REV9000 isokinetic dynamometer can be used in future sports performance studies. A low-to-moderate reliability was found in the isokinetic strength bilateral ratios while the Hamstring:Quadricep concentric ratio showed moderate reliability. The highest reliability (>0.90) was observed in the dynamic control ratio (Hamstring eccentric:Quadricep concentric) which consequently confirms that it is a more valid indicator for imbalanced reciprocal parameters and can be used in rehabilitation and sports medicine.
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