Category Archives: Dumbbell

28-Hz Vibration on Arm

Med Sci Sports Exerc. 2009 Mar;41(3):645-53. doi: 10.1249/MSS.0b013e31818a8a69.

The effects of a 28-Hz vibration on arm muscle activity during isometric exercise.

Mischi M, Cardinale M.


Department of Electrical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands.



The aim of this study was to evaluate activation and coactivation of biceps and triceps muscles during isometric exercise performed with and without superimposing a vibration stimulation.


Twelve healthy volunteers (age = 22.7 +/- 2.6 yr) participated in this study. The subjects performed five trials of isometric elbow flexion and five trials of elbow extension with increasing levels of force in two conditions: vibration (V) and normal loading (C). V stimulation was characterized by a frequency of 28 Hz. Surface EMG activity of biceps and triceps muscles was simultaneously measured by bipolar surface electromyography and assessed by the estimation of the root mean square (RMS) of the electrical recordings over a fixed 5-s interval. Frequency analysis was adopted to estimate the RMS related to muscle activation and to exclude the harmonics generated by movement artifacts due to V.


The analysis of the recordings revealed a significant EMG RMS increase when V was applied. On average, the EMG RMS of biceps and triceps during elbow flexion was, respectively, 26.1% (P < 0.05) and 18.2% (P = 0.15) higher than C. During elbow extension, the EMG RMS of biceps and triceps was 77.2% and 45.2% (P < 0.05) higher than C, respectively. The coactivation was assessed as the ratio between the activation of antagonist and agonist muscles during arm flexion and extension tasks. The results revealed an increase of coactivation during V exercise, especially for lighter loads.


This study shows that V exercise at 28 Hz produces an increase of the activation and the coactivation of biceps and triceps. This exercise modality seems therefore suitable for various applications.

PMID: 19204585

Vibration Effects Shoulder Motion

Int J Sports Med. 2009 Dec;30(12):868-71. doi: 10.1055/s-0029-1238288.

Handheld vibration effects shoulder motion.

Tripp BL, Eberman LE, Dwelly PM.


University of Florida, Applied Physiology & Kinesiology, Gainesville, USA.


We explored effects of handheld vibration on glenohumeral motion in competitive overhead-throwing athletes. We used a randomized, blinded pre-test post-test cross-over design. Each arm of each subject experienced 2 conditions (1-control, 1-experimental), each with pre-test and post-test measures; the order of which was randomized. Participants included Division-I baseball and softball players (n=35: age=20+/-2 yr, height=178+/-9 cm, mass=84+/-12 kg, years of sport participation=13+/-4 yrs). During the experimental condition, participants held a vibrating (2.2 mm, 15 Hz, 20 s), 2.55 kg (5.62 lbs) Mini-VibraFlex dumbbell in neutral glenohumeral rotation. During the control condition, participants held the still dumbbell (0 mm, 0 Hz, 20 s). Participants rested one min after each trial (3). We used a digital protractor to assess range of motion bilaterally, employing a standard technique for measuring maximal internal (IR) and external rotation (ER). Repeated-measures analyses of variance indicated that range of dominant IR increased 6.8% ( P=0.001, ES=0.16) after handheld vibration. Handheld vibration did not affect range of dominant ER ( P>0.05, 1-beta=0.20), non-dominant IR ( P>0.05, 1-beta=0.41), or non-dominant ER ( P>0.05, 1-beta=0.05).

Short bouts of handheld vibration increased dominant IR in collegiate baseball and softball athletes.These results suggest that handheld vibration may help maintain glenohumeral IR that is vital to the healthy and competitive throwing shoulder.

PMID: 19885779

Vibration Effects Mechanical Power & EMG

Eur J Appl Physiol Occup Physiol. 1999 Mar;79(4):306-11.

Influence of vibration on mechanical power and electromyogram activity in human arm flexor muscles.

Bosco C, Cardinale M, Tsarpela O.


University of Rome-Tor Vergata, Fondazione Don Gnocchi, Italy.


The aim of this study was to evaluate the influence of vibration on the mechanical properties of arm flexors. A group of 12 international level boxers, all members of the Italian national team, voluntarily participated in the experiment: all were engaged in regular boxing training. At the beginning of the study they were tested whilst performing forearm flexion with an extra load equal to 5% of the subjects’ body mass. Following this. one arm was given the experimental treatment (E; mechanical vibration) and the other was the control (no treatment). The E treatment consisted of five repetitions lasting 1-min each of mechanical vibration applied during arm flexion in isometric conditions with 1 min rest between them. Further tests were performed 5 min immediately after the treatment on both limbs. The results showed statistically significant enhancement of the average power in the arm treated with vibrations. The root mean square electromyogram (EMGrms) had not changed following the treatment but, when divided by mechanical power, (P) as an index of neural efficiency, it showed statistically significant increases. It was concluded that mechanical vibrations enhanced muscle P and decreased the related EMG/P relationship in elite athletes. Moreover, the analysis of EMGrms recorded before the treatment and during the treatment itself showed an enormous increase in neural activity during vibration up to more than twice the baseline values.

This would indicate that this type of treatment is able to stimulate the neuromuscular system more than other treatments used to improve neuromuscular properties.

PMID: 10090628

Vibration + Isometric Contractions

J Strength Cond Res. 2004 Nov;18(4):777-81.

Effect of vibration during fatiguing resistance exercise on subsequent muscle activity during maximal voluntary isometric contractions.

McBride JM, Porcari JP, Scheunke MD.


Musculoskeletal Research Center, Department of Exercise and Sport Science, University of Wisconsin-La Crosse, La Crosse, WI 54601, USA.


This investigation was designed to determine if vibration during fatiguing resistance exercise would alter associated patterns of muscle activity. A cross-over design was employed with 8 subjects completing a resistance exercise bout once with a vibrating dumbbell (V) (44 Hz, 3 mm displacement) and once without vibration (NV). For both exercise bouts, 10 sets were performed with a load that induced concentric muscle failure during the 10th repetition. The appropriate load for each set was determined during a pretest. Each testing session was separated by 1 week. Electromyography (EMG) was obtained from the biceps brachii muscle at 12 different time points during a maximum voluntary contraction (MVC) at a 170 degrees elbow angle after each set of the dumbbell exercise. The time points were as follows: pre (5 minutes before the resistance exercise bout), T1-T10 (immediately following each set of resistance exercise), and post (15 minutes after the resistance exercise bout). EMG was analyzed for median power frequency (MPF) and maximum (mEMG). NV resulted in a significant decrease in MPF at T1-T4 (p < or 0.05) and a significant increase in mEMG at T2 during the MVC. V had an overall trend of lower mEMG in comparison to NV. The mEMG and MPF values associated with NV were similar to previously reported investigations. The lower mEMG values and the higher MPF of V in comparison to NV are undocumented.

The EMG patterns observed with vibration may indicate a more efficient and effective recruitment of high threshold motor units during fatiguing contractions. This may indicate the usage of vibration with resistance exercise as an effective tool for strength training athletes.