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Power Balance flunks scientific tests.

A controlled trial of college athletes has found that wearing a Power Balance bracelet did not enhance their performance. The study, sponsored by the American Council on Exercise (ACE), was conducted by John Porcari, Ph.D. and other researchers from the University of Wisconsin. Each athlete completed two trials of four tests: trunk flexibility, balance, strength and vertical jump. 

For one trial, the subjects wore a Power Balance bracelet ($30), and for the other they wore a placebo ($0.30 rubber bracelet). The order of bracelets worn was completely randomized and double-blinded so that neither the subjects nor the examiners knew which bracelet was being worn for which trial. Analysis of the data showed no significant difference in  flexibility, balance, strength, or vertical-jump height between the Power Balance and placebo trials. Curiously, the subjects did better in the second trial than the first, a phenomenon called the "order effect." ACE's report stated: 

"The improvements in the second trials were attributed to the fact that subjects were either: (1) more warmed up, or (2) habituated to the task. This would explain why the public sales demonstrations of Power Balance and similar performance-jewellery products appear to have beneficial effects on flexibility, balance and strength. But in reality, these sales demonstrations are essentially carnival tricks. By altering the way you apply force to the body, explains Porcari, you can easily change the outcome. 'If I'm pushing a certain direction, and then I change the angle of pull or push a little bit, I can get you to lose your balance easily,' he says."

[Porcari JP and others. Power Balance or power of persuasion? ACE Web site, March 2011]

https://www.acefitness.org/certifiednews/images/article/pdfs/ACEPowerBalanceStudy.pdf 

Power Balance reportedly has sold three million units during the past three years. In December 2010, the Australia Competition and Consumer Commission (ACCC) announced that Power Balance Pty Australia admitted that there is no credible scientific basis for the claims and therefore no reasonable grounds for making representations about its wristbands being beneficial [6]. To settle ACCC's concerned, the company signed an undertaking in which it promised to stop making unsupportable claims and to offer refunds to consumers who feel they have been misled.

For a detailed account of the product's history, see http://www.devicewatch.org/reports/power_balance.shtml

Extracted from: Consumer Health Digest #11-06 March 24, 2011

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