Different types of mechanical vibration application on EMG response and strength performance

Abstract Aim: The present study aimed to compare the strength performance and the neuromuscular activity during one maximum repetition test (1RM), and the maximum voluntary isometric contractions (MVIC) performed with whole-body vibration (WBV), local vibration (LV), and no vibration (NV). Methods: The sample consisted of 15 males, experienced in strength training for at least 6 months, which performed all strength tests in the barbell curl exercise across randomized trials on the following conditions: NV, WBV, and LV. During all tests, the normalized root means square values of the electromyographic signals (EMGRMS) of the biceps brachii and brachioradialis were recorded and compared between the conditions. The one-way ANOVAs with repeated measures were used to compare the results of 1RM and MVIC tests and the normalized EMGRMS between the conditions. When necessary, a post hoc Scott-Knott test was used to identify the differences reported in the ANOVAs. The significance level adopted was α < 0.05. Results: The EMGRMS response of the biceps brachii and brachioradialis muscles during the 1RM and MVIC tests presented significantly higher values at LV compared to WBV, and NV (p < 0.001). The 1RM tests, and the MVIC results were similar between conditions (p = 0.9803; p = 0.061, respectively). Conclusion: These results indicate that the application of MV was not sufficient to increase strength performance.

Individual Responses to Different Vibration Frequencies Identified by Electromyography and Dynamometry in Different Types of Vibration Application.

ABSTRACT: Oliveira, MP, Menzel, H-JK, Cochrane, DJ, Drummond, MD, Demicheli, C, Lage, G, and Couto, BP. Individual responses to different vibration frequencies identified by electromyography and dynamometry in different types of vibration application. J Strength Cond Res 35(6): 1748-1759, 2021-The application of mechanical vibration is a common neuromuscular training technique used in sports training programs to generate acute increases in muscle strength. The principal aim of the study was to compare the individual optimal vibration frequency (IOVF) identified by electromyography (EMG) activity and force production in strength training. Twenty well-trained male volunteers (age: 23.8 ± 3.3 years) performed a familiarization and 2 interventions sessions, which included 5 maximal voluntary contractions (MVCs) of the elbow flexors with a duration of 10 seconds and 5-minute intervals between each MVC. The first MVC was performed without vibration followed by 4 randomized MVCs with application of vibration in the direction of the resultant muscle forces' vector (VDF) or whole-body vibration (WBV) at frequencies of 10, 20, 30, or 40 Hz. The mechanical vibration stimulus was superimposed during the MVC. Individual optimal vibration frequency, as identified by EMG, did not coincide with IOVF identified by force production; low agreement was observed between the vibration frequencies in generating the higher EMG activity, maximal force, and root mean square of force. These findings suggest that the magnitude of the vibratory stimulus response is individualized. Therefore, if the aim is to use acute vibration in conjunction with strength training, a preliminary vibration exposure should be conducted to determine the individualized vibratory stimulus of the subject, so that training effects can be optimized.

Effects of Local Vibration on Dynamic Strength Training.

ABSTRACT: Drummond, MDM, Couto, BP, Oliveira, MP, and Szmuchrowski, LA. Effects of local vibration on dynamic strength training. J Strength Cond Res 35(11): 3028-3034, 2021-The study aim was to compare the chronic effects of maximal dynamic strength training with and without the addition of local vibration (LV) on maximal force generation and hypertrophy of the elbow flexor muscles in trained subjects. Twenty men were divided into 2 groups (conventional training [CT] group and vibration training [VT] group). The CT group performed conventional maximal dynamic strength training, and the VT group performed maximal dynamic strength training with mechanical vibrations (frequency of 26 Hz and amplitude of 6 mm). CT and VT groups performed 5 sets of 3-4 repetitions, with 2-minute rest intervals between sets. The subjects trained 3 times per week for 12 weeks. After the training period, the CT group presented a significant increase in the mean 1 repetition maximum (1RM) value in the elbow flexion exercise in the orthostatic position (EFO) (7.2 ± 1.5%) (p < 0.0001) and elbow flexion exercise using the Scott bench (EFSB) (6.3 ± 1.8%) (p < 0.0001). The VT group also showed significant increases in 1RM values in the EFO (6.87 ± 0.8%) (p < 0.0001) and EFSB (6.56 ± 1.4%) (p < 0.0001). The CT group presented a significant increase in the mean maximal voluntary isometric contraction (MVIC) value after the training period (8.2 ± 2.3%) (p < 0.0001). The VT group also showed a significant increase in the mean MVIC value after training (9.1 ± 2.4%) (p < 0.0001). After the training period, both groups presented a significant increase in the mean value of elbow flexor thickness (CT = 5.6 ± 3.5%, VT = 5.1 ± 2.8%) (p = 0.001). The increases in 1RM, MVIC, and muscle thickness were statically similar between groups. Therefore, the addition of LV does not represent an additional stimulus for individuals trained in dynamic maximal strength training.

Content Validation of a Catalog of Exercises for Judo.

This study aimed to assess the content validity of a catalog of 76 judo exercises. Two groups of raters comprising 16 judo experts evaluated the following content validity indicators: Clarity of Language, Practical Pertinence, Theoretical Relevance, and the Dimension of each exercise. The results confirmed the content validity of the judo training catalog with indicators showing scores greater than 0.80. These findings suggest that all 76 judo exercises are pertinent, representative of judo training and understandable for judo coaches. Thus, this catalog of judo exercises may help judo coaches in the selection and recording of exercises.

Effect of strength training on regional hypertrophy of the elbow flexor muscles.

INTRODUCTION: Muscle hypertrophy is the main structural adaptation to strength training. We investigated the chronic effects of strength training on muscle hypertrophy in different regions of the elbow flexor muscles. METHODS: Eleven untrained men (21.8 ± 1.62 years) underwent magnetic resonance imaging to determine the proximal, medial, distal, and mean cross-sectional areas (CSA) of the elbow flexors. The volunteers completed 12 weeks of strength training. The training protocol consisted of 4 sets of 8-10 maximum repetitions of unilateral elbow flexion. The interval between sets was 120 s. The training frequency was 3 sessions per week. RESULTS: The magnetic resonance images verified the presence of significant and similar hypertrophy in the distal, medial, and proximal portions of the elbow flexor muscles. CONCLUSIONS: Muscle hypertrophy may be assessed using only the medial CSA. We should not expect different degrees of hypertrophy among the regions of the elbow flexor muscles. Muscle Nerve 54: 750-755, 2016.

Effects of 12 weeks of dynamic strength training with local vibration.

The purpose of this study was to investigate the chronic effects of dynamic strength training (ST) with local vibration on the maximum strength of elbow flexor muscles. Twenty healthy male untrained volunteers were divided randomly into the following two groups: the conventional training group (CTG) or the vibration training group (VTG). Both groups performed ST for 12 weeks, three times a week. The ST protocol included four sets of 8-10 repetition maximums (RMs) of unilateral elbow flexion exercise. The VTG performed this training protocol with local vibration at a frequency of 30 Hz and amplitude of 6 mm. The mean values of the one repetition maximum (1RM) tests for both groups increased significantly from the pretest week to the fourth week and from the fourth week to the eighth week (CTG: mean 19.02, s = 7.88%, p = 0.01; mean 10.50, s = 6.86%, p = 0.019, respectively; VTG: mean 16.02, s = 8.30%, p = 0.017; mean 12.55, s = 8.76%, p = 0.019, respectively). The increases in the maximal voluntary contraction (MVC) tests were also statistically significant from the pretest week to the fourth week and from the fourth week to the eighth week (CTG: mean 12.32, s = 8.33%, p = 0.004; mean 9.95, s = 5.32%, p = 0.006, respectively; VTG: mean 10.16, s = 11.71%, p = 0.003; mean 10.36, s = 2.96%, p = 0.01, respectively). There was no significant difference between the 1RM and MVC test results in the eighth and twelfth weeks in either group. No significant differences were observed between the groups (p < 0.05). In conclusion, the application of local vibration does not change the chronic effects of dynamic ST in untrained individuals.

Effects of mechanical vibration applied in the opposite direction of muscle shortening on maximal isometric strength.

Most studies about human responses to mechanical vibrations involve whole-body vibration and vibration applied perpendicularly to the tendon or muscle. The aim of the present study was to verify the effects of mechanical vibration applied in the opposite direction of muscle shortening on maximal isometric strength of the flexor muscles of the elbow due to neural factors. Conventional isometric training with maximal isometric contractions (MVCs) and isometric training with vibrations were compared. Nineteen untrained males, ages 24 +/- 3.28 years, were divided into 2 training groups. Group 1 performed conventional isometric training and group 2 isometric training with mechanical vibrations (frequency of 8 Hz and amplitude of 6 mm). Both groups executed 12 MVCs with a duration of 6 seconds and 2-minute intervals between the repetitions. The subjects trained 3 times per week for 4 weeks. The strength of the group subjected to vibrations increased significantly by 26 +/- 11% (p < 0.05), whereas the strength of the group with conventional isometric training increased only 10 +/- 5% (p < 0.05). These data suggest that training with vibrations applied in the opposite direction of muscle shortening enhances the mechanism of involuntary control of muscle activity and may improve strength in untrained males. Since these findings were in untrained males, further studies with athletes are necessary in order to generalize the results to athletes' training, although it seems that it would be possible.