The Influence of Preset Frequency, Loading Condition, and Exercise Type on the Mechanical Behavior of a Novel Vibratory Bar

Abstract

This study aimed to analyze the influence of different vibration frequencies, loading conditions, and exercise types on the mechanical behavior of a novel vibratory bar (VB). Fourteen healthy men were asked to hold the VB during lying row (pulling) and bench press (pushing) static exercise as steadily as possible for 10 seconds with loads of 20, 50, and 80% of the maximum sustained load (MSL) and at preset vibration frequencies (f(in)) of 20, 35, and 50 Hz. Root mean square vibration acceleration (a(RMS)), peak-to-peak displacement (D), and frequency (f(out)) were gained from a 3-dimensional accelerometer fixed to the VB. Increasing vibration frequency (from 20 to 50 Hz) resulted in a progressive and sizeable increase in VB a(RMS) and f(out) (both p ≤ 0.001) with smaller variations of D (≤5.9%, p ≤ 0.001). Adding weight to the VB (progressive overload from 20 to 80% MSL) did not affect D and minimally altered a(RMS) (<4.2%, p = 0.014) and f(out) (<1.7%, p = 0.002). Altering the type of exercise (pulling vs. pushing) did not affect VB a(RMS), D, and f(out). In conclusion, this study establishes the validity of a novel VB and legitimates its use for effective and safe upper-body static exercise with a wide range of vibration frequencies and loading conditions in the context of physical training or rehabilitation.

Effect of vibration frequency on agonist and antagonist arm muscle activity

“…Again, this could be partly explained by differences between vibrating devices in stimulus transmission, resulting in a different vibration damping effect across loads. The acceleration and peak-to-peak displacement of our vibratory bar were hardly influenced by overloading partly because the vibration source was mounted directly onto the bar (Rodríguez-Jiménez et al 2014). In contrast, the vibration transmissibility of the device used by Mischi and Cardinale (2009) is clearly tension-dependent because the sinusoidal vibrations are produced by an electromagnetic generator and mechanically transmitted to the hands through belts; an excessive damping effect onto the belts during the lower levels of muscular tension could partly explain the absence of vibration effects they observed.…”

“…An-inverter (Omron Sysdrive 3G3JV, single phase 230 V, 0.55 kW) was used to reduce the speed of the motor (3,000 rpm) according to the required frequency. The two extremities of the vibratory bar were attached to the guide rails of a pneumatic resistance system (Keiser Half Rack, Fresno, CA) by means of carabineers, which allowed pneumatic pulleys to roll seamlessly with the movement of the bar (Rodríguez-Jiménez et al 2014). …”

“…Cardinale 2009) and more recently vibratory bars (Moras et al 2010;Poston et al 2007;Rodríguez-Jiménez et al 2014) have also been specifically designed for upper limb vibration exercise. One of the main features of the vibratory stimulus is that it has been shown to acutely improve specific aspects of neuromuscular performance like maximal power output (Bosco et al 1999;Cochrane et al 2008;Issurin and Tenenbaum 1999;Poston et al 2007), maximal strength (Liebermann and Issurin 1997) and muscle activity, as evaluated with surface electromyography (EMG) (Bosco et al 1999;Mischi and Cardinale 2009;Moras et al 2010).…”

“…The EMG data reported in the present study were collected in our previous work (Rodríguez-Jiménez et al 2014). Based on the existing literature, we formulated the following hypotheses: (1) vibration exercise would result in greater agonist activation and antagonist coactivation than non-vibration exercise; (2) the expected vibration-induced increase in agonist activation and antagonist coactivation would be proportional to the vibration frequency and (3) would occur regardless of the applied load.…”