AVIBRATORY BAR FOR UPPER BODY: FEASIBILITY AND ACUTE EFFECTS ON EMGrms ACTIVITY GERARD MORAS, 1 SERGIO RODRI ´ GUEZ-JIME ´ NEZ, 1 JULIO TOUS-FAJARDO, 1 DANIEL RANZ, 1 AND IN ˜ IGO MUJIKA 2,3 1 Sports Performance Lab, National Institute of Physical Education, Barcelona, Spain; 2 USP—Araba Sport Clinic, Vitoria-Gasteiz, Basque Country, Spain; and 3 Department of Physiology, Faculty of Medicine and Odontology, University of the Basque Country (UPV-EHU), Spain ABSTRACT Moras, G, Rodrı ´guez-Jime ´ nez, S, Tous-Fajardo, J, Ranz, D, and Mujika, I. A vibratory bar for upper body: Feasibility and acute effects on EMGrms activity. J Strength Cond Res 23(x):000– 000, 2009—The purpose of this study was to determine the feasibility of a purpose-designed vibratory bar (VB) as a potential vibration training device and thereafter to assess its effects on upper-body muscles’ electromyographic (EMG) activity during vibration. During session 1, 16 physically active males held the VB during the bench press exercise in an isometric extended position (EP) in the following vibration conditions selected in the inverter ( i ): no vibration (0), 20, 30, 40, and 50 Hz i . Maximal acceleration (Acc max ), frequency (Freq), and peak-to-peak amplitude (Amp p-p ) obtained at the center (C) and at the end (E) of the VB were assessed using an accelerometer. During session 2, EMGrms of the triceps, deltoid, and pectoralis major were recorded in EP and isometric flexion position (FP) at 0, 25, and 45 Hz i . The Acc max , Freq, and Amp p-p values ranged from 37.4 to 96.4 mÁs 22 , 18.5 to 30.8 Hz, and 4.6 to 6.1 mm, respectively. The accelerometer’s position had a significant effect on the Acc max and Amp p-p . All Freq obtained at C and E were different (p , 0.001) to the Freq i . An increase (p , 0.05) in EMGrms was observed in both vibration conditions compared with 0 Hz i , except during 25Hz i for deltoid and pectoralis muscle in FP. Although no significant differences were found in any of the muscles between 45 Hz i and 25Hz i , the highest EMGrms was elicited at 45Hz i . Although the registered VBs’ parameters seem appropriate for vibration training, the frequency in the FP should be higher than 25 Hz i to induce significant increases in EMGrms in deltoid and pectoralis muscles. The use of a vibratory bar may be a suitable system to simultaneously stimulate upper-body muscles. KEY WORDS vibration exercise, neuromuscular, posture, strength, reflex INTRODUCTION V ibration training has been promoted during the last decade as an alternative and complementary method to resistance training (26,32). A number of studies have examined its effects on several physiologic systems, including the neuromuscular (38), endocrine (6), cardiovascular (37), sensory (30), circulatory (27), and bone systems (16). Vibratory stimuli can be applied directly to the targeted tendon (24,28) or muscle belly (18,20) or indirectly through a part of the body to the target muscle(s) (34) in either the lower- (9,33) or upper-body extremities (4,8,19). In the most common and well-investigated indirect method, a subject stands on a vibration platform that transmits the vibration to all the muscles of the lower extremities (38) via the feet. In this case the vibration signal is attenuated during its transmission through soft tissues, which are capable of absorbing and dampening the vibration (15). This means that the amplitude of vibration could be very small in the target muscle and may be insufficient to elicit a training effect (34), especially at the more distant muscles. In contrast, when vibration is directly applied to the tendon or muscle belly, the attenuation of vibration by transmission is much lower (24). The acute response of the neuromuscular system to different vibration loads may be analyzed by EMG measure- ments. It is well known that sustained vibration applied to a muscle or tendon can stimulate muscle spindles and elicit a tonic vibration reflex (TVR) primarily via Ia monosynaptic and polisynaptic pathways (12,28). However, as stated earlier, it is important to separate research using the direct applica- tion of a vibration signal at the surface of the muscle/tendon unit or an indirect application through platforms or dumb- bells. Nevertheless, several studies have reported an increase in EMG activity in both lower- (2,5,17,38) and upper-body muscles (4,24), but to our knowledge, only 4 studies have No funding was received for this work from any organization. Address correspondence to Dr. Gerard Moras, gmoras@gencat.net. 0(0)/1–11 Journal of Strength and Conditioning Research Ó 2009 National Strength and Conditioning Association VOLUME 0 | NUMBER 0 | MONTH 2009 | 1