Perceptual & Motor Skills: Exercise & Sport 2013, 117, 2, 353- 357. © Perceptual & Motor Skills 2013
THE EFFECT OF A SILICONE WRISTBAND IN DYNAMIC BALANCE1 THIAGO TOSHI TERUYA, BRUNO MACHADO MATARELI, FILLIPE SOARES ROMANO, AND LUIS MOCHIZUKI School of Arts, Sciences and Humanities University of São Paulo Summary.—The eﬀect of a wristband on the dynamic balance of young adults was assessed. Twenty healthy young adults wore a commercial Power BalanceTM or fake silicone wristband. A 3D accelerometer was attached to their lumbar region to measure body sway. They played the video game Tightrope (Wii® video game console) with and without a wristband; body sway acceleration was measured. Mean balance sway acceleration and its variability were the same in all conditions, so silicone wristbands do not modify dynamic balance control.
Anecdotal evidence2 suggests that wearing a silicone wristband increases balance control; the producers of such a silicone wristband claim that the hologram attached to the wristband is capable of balancing the metaphysical energies of the human body to improve human performance in several sport activities. Previous studies (Brice, Jarosz, Ames, & Da Costa, 2011; Pérez & Vicén, 2011) showed that static and dynamic balance functional performance were not improved when the participants wore such a silicone wristband. Pothier, Thiel, Khoo, Dillon, Sulway, and Rutka (2012) and Verdan, Marzili, Barna, Roquemore, Fenter, Blujus, et al. (2012) did not find any eﬀect of the wristband on balance sway in a quiet standing posture. Postural control (Mochizuki, Duarte, Amadio, Zatsiorsky, & Latash, 2006; Hamill & Knutzen, 2009) supports the body weight against gravity, balances the center of mass in static and dynamic conditions, keeping the horizontal projection of the center of mass over the support base, and counteracts internal and external mechanical perturbations of body position. Posture changes and muscle activation, expressed as body sway, are used in balance control and to counteract mechanical perturbations. Studies (Brice, et al., 2011; Pérez & Vicén, 2011) of postural eﬀects of silicone wristbands have not addressed body sway during dynamic balance tasks. In this study, a dynamic balance task was designed to challenge postural control under a condition similar to sport activities. The goal was to evaluate the eﬀect of a silicone wristband on body sway during a virtual reality dynamic balance task using a video game console. Address correspondence to Luis Mochizuki, School of Arts, Sciences and Humanities, University of São Paulo, Av. Arlindo Béttio, 1000, 03829-000, São Paulo/SP, Brazil or e-mail ([email protected]
Retrieved December 10, 2011, from http://www.powerbalance.com/about-us.
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Hypothesis. Body sway will not be aﬀected by wearing the silicone wristband during the dynamic balance task. METHOD In this double-blind, placebo-controlled study, participants were randomly assigned to placebo and experimental groups. The participants (N = 20; 11 men, 9 women; M age = 23.2 yr., SD = 4.0; M weight = 70.5 kg, SD = 18.1; M height = 169.3 cm, SD = 8.47) did not know whether they had a real or fake Power Balance® wristband. Those who explained the task and controlled the acquisition system were not aware of the condition for each participant. Inclusion criteria were: age between 20 and 35 years; no disease or injury aﬀecting balance; engage in sports or physical exercise at least twice per week for 30 min./session. The exclusion criteria were: practice of ballet, gymnastics, skateboarding, judo or other sport activity in which the control of static postures are necessary to performance; inability to perform or to understand the balance task; taking three or more medicines; visual problems not corrected by glasses; deafness. Participants gave written informed consent to engage in the study, and this study was approved by a local ethics committee. Participants wore a silicone wristband (fake or Power Balance®) while playing the videogame Tightrope (Wii Fit®). The fake wristband was similar in size and weight to the Power Balance® wristband, but its hologram was not designed according to Eastern philosophies. To record body sway, a 3-cmside-cubic-3D accelerometer (EMG System Brazil Ltda.) was attached over the sacrum so that one accelerometer axis was vertical and the other two components parallel to the ground, to measure anterior-posterior (AP) and medio-lateral (ML) body sway. The acceleration signal was recorded during the whole task using a 16-channel acquisition system which sampled the data at 100 Hz. The task was to play the Tightrope (Nintendo Wii Fit®), in which the participant crosses a virtual aerial space between two buildings walking on a rope. The participant stood in the upright position, over the Wii Balance Board®, 2.5 m away from a 50” digital TV monitor. Virtual movement along the imaginary rope during this game is guided by the real movements of the participant standing on the board. Participants could move the body or even take a foot oﬀ the board, but not touch the ground. The Wii balance platform measures the vertical ground reaction force and estimates the position of the center of mass, to control the virtual movements of the player displayed on the TV monitor. Participants performed the task twice, with and without a wristband, in counterbalanced order. They had foreknowledge about the supposed eﬀects of the Power Balance®, but they were not aware that one of the wristbands was fake. The acceleration time series of the body sway was low-pass filtered with a digital 4th-order Butterworth filter at 20 Hz. The mean acceleration intensity (the root mean square) and the mean acceleration variability (mean standard
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deviation) of the time series were calculated. For both variables, a Kruskal Wallis test (H) analyzed the eﬀect of condition (Power Balance® wristband, fake wristband, no wristband) for each body sway direction (Vertical, Anterior-Posterior, Medio-Lateral). Alpha was set at .05. RESULTS AND DISCUSSION For the three body sway directions, the mean intensity acceleration was not aﬀected by condition (Vertical: H = 1.9, p = .37; Anterior-Posterior: H = 2.3, p = .31; Medio-Lateral: H = 2.0, p = .35; Cohen’s d range: –.27 to .94, eﬀect
FIG. 1. (A) Mean acceleration of body sway and (B) mean standard deviation of the acceleration of body sway in Anterior-Posterior, Medio-Lateral and Vertical directions during the no wristband (hashed bars), Power Balance® wristband (white bars), and fake wristband (gray bars) conditions.
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sizes r range: –.13 to .42) and the mean standard deviation acceleration was also not aﬀected by condition (Vertical: H = 1.9, p = .37; Anterior-Posterior: H = 2.2, p = .33; Medio-Lateral: H = 1.9, p = .38; Cohen’s d range: –.11 to 1.2, eﬀect sizes r range: –.05 to .53). Body sway parameters during the dynamic task did not change when the person wore a wristband (Fig. 1) (Cohen’s d range: –.05 to .05, eﬀect sizes r range: –.02 to .02). This supports other studies (Pothier, et al., 2012: Cohen’s d range: –.23 to .03, eﬀect size’s r range: –.11 to .01; Verdan, et al., 2012: Cohen’s d range: –.05 to .05, eﬀect sizes r range: –.02 to .02) reporting no eﬀect of a wristband on body sway during static postural tasks. Tests of functional balance have shown equivocal eﬀects on postural control of wearing a silicone wristband. Porcari, Hazuga, Foster, Doberstein, Becker, Kline, et al. (2011) reported that college football athletes presented better strength performance, flexibility, and balance when they wore a silicone wristband (placebo or non-placebo) (Cohen’s d range: –.16 to .06, eﬀect sizes r range: –.008 to .03). However, there may have been an eﬀect of warm-up exercises and task familiarization, and Pérez & Vicén (2011) did not show any eﬀect of the Power Balance® wristband or placebo on static and dynamic balance (Cohen’s d range: –.8 to .08, eﬀect sizes r range: –.37 to .04). In addition, in a double blind study using the Power Balance® wristband or placebo, Henschel, Boutagy, Gabbard, Sam, Griﬃths, Carney, et al. (2011) found no eﬀect on strength, balance, or flexibility. The silicone wristband also did not change the variability of body sway. In general, the participant’s low confidence or hesitancy leads to increased variability. Therefore, this result suggests that the participant's confidence to perform the virtual reality task was not aﬀected by the wristband. Neither was the acceleration of the body sway aﬀected by either silicone wristband: the dynamics of the body sway were equivalent under the two wristband conditions. In summary, there is no evidence that wearing a silicone wristband changes body sway to improve performance of a balance task. REFERENCES
BRICE, S. R., JAROSZ, B. R., AMES, R. A., & DA COSTA, C. (2011) The eﬀect of close proximity holographic wristbands on human balance and limits of stability: a randomized, placebo-controlled trial. Journal of Bodywork & Movement Therapies, 15, 298-303. HAMILL, J., & KNUTZEN, K. M. (2009) Biomechanical basis of human movement. (3rd ed.) Baltimore, MD: Lippincott Williams & Wilkins. HENSCHEL, M., BOUTAGY, N., GABBARD, A., SAM, M., GRIFFITHS, K., CARNEY, C., MANIGUET, E., PETERS, A., KATAE, D., WYGAND, J. W., & OTTO, R. M. (2011) The eﬀect of embedded holographic technology on balance, strength and flexibility. Medicine and Science in Sports and Exercise, 43, 913.
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MOCHIZUKI, L., DUARTE, M., AMADIO, A. C., ZATSIORSKY, V. M., & LATASH, M. (2006) Changes in postural sway and its fractions in conditions of postural instability. Journal of Applied Biomechanics, 22, 51-60. PÉREZ, F. V., & VICÉN, J. A. (2011) Eﬀects of Power Balance® in static and dynamic balance in physically active subjects. Apunts Medicina de L'Esport, 171, 109-115. PORCARI, J., HAZUGA, R., FOSTER, C., DOBERSTEIN, S., BECKER, J., KLINE, D., MICKSCHL, T., & DODGE, C. (2011) Can the Power Balance® bracelet improve balance, flexibility, strength and power? Journal of Sports Science and Medicine, 10, 230-231. POTHIER, D. D., THIEL, G., KHOO, S. G., DILLON, W. A., SULWAY, S., & RUTKA, J. A. (2012) Eﬃcacy of the Power Balance® silicone wristband: a single-blind, randomized, triple placebo-controlled study. Journal of Otolaryngology-Head & Neck Surgery, 41, 153-159. VERDAN, P. J. R., MARZILI, T. S., BARNA, G. I., ROQUEMORE, A. N., FENTER, B. A., BLUJUS, B., & GOSSELIN, K. P. (2012) Eﬀect of the Power Balance® band on static balance, hamstring flexibility, and arm strength in adults. Journal of Strength and Conditioning Research, 26, 2113-2118. Accepted September 17, 2013.
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