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Randomized Controlled Trial
. 2018 Sep 1;18(3):339-347.

Does the motor unit synchronization induced by vibration enhance maximal voluntary isometric contraction force? A randomized controlled double-blind trial

Seher Kara  1 , Ilhan Karacan, Muharrem Cidem, Emel Saglam Gokmen, Safak S Karamehmetoğlu
Affiliations
Randomized Controlled Trial

Does the motor unit synchronization induced by vibration enhance maximal voluntary isometric contraction force? A randomized controlled double-blind trial

Seher Kara et al. J Musculoskelet Neuronal Interact. .

Abstract

Objectives: Motor unit synchronization has been proposed as a potential mechanism underlying muscle strength gains for vibration training, but it has yet to be definitely demonstrated. Aim of this study was to determine whether motor unit synchronization induced by vibration has an effect on isometric muscle strength.

Methods: Thirty-six healthy volunteers were randomized into two groups: the vibration and the control (sham vibration) groups. Two sets of test measurements and vibration resistance training between the two sets were applied to the right wrist flexors. The maximal voluntary isometric contraction force, and flexor carpi radialis EMG activity were recorded in the first (without vibratory stimulation) and the second (with vibratory stimulation) set.

Results: There was no difference in the normalized peak force between the first and the second set in the vibration group (p=0.554). Motor units fired with maximal voluntary isometric contraction synchronized at the vibration frequency (25 Hz) during vibration in all participants of the vibration group.

Conclusion: The present study indicates that vibration-induced motor unit synchronization does not have a significant effect on the maximal voluntary isometric contraction force.​.

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Conflict of interest statement

The authors have no conflict of interest.

Figures

Figure 1
Figure 1
Study flow diagram: Pre-training MVICs without vibration (1.set), vibration resistance training and post-training MIVCs with vibration (2.set). After the first set, 30% of the MVIC trial with the highest peak force value was determined as a threshold for the submaximal isometric exercise. The horizontal dashed line shows the threshold. P1-P6: training periods.
Figure 2
Figure 2
Experimental setup: a) To apply real vibration, the steel rope was connected to the vibration platform b) To apply the sham vibration, the steel rope was fixed a hook on the side wall of the exercise table.
Figure 3
Figure 3
Error bars with 95% confidence interval of the normalized muscle strength.
Figure 4
Figure 4
Representative frequency spectrograms of vibration (4a, 4b) and SEMG signals (4c, 4d) for a participant of the vibration group. Fig 4c: A prominent peak frequency of a pre-training MVIC at 10.7 Hz. Fig 4d: The prominent peak during real vibration at the vibration frequency (25 Hz) due to synchronization.
Figure 5
Figure 5
Representative frequency spectrograms of vibration (5a, 5b) and SEMG signals (5c, 5d) for a participant of the Control group. Fig 5c: A prominent peak frequency of a pre-training MVIC at 12.7 Hz. Fig 5d: The prominent peak during sham vibration at 12.7 Hz.
See this image and copyright information in PMC

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