In a recent decision, the National Advertising Division recommended that Reebok discontinue certain claims for its EasyTone toning shoe line made in print and Internet advertising.

Although the decision was not prompted by a competitor challenge, the NAD nevertheless requested substantiation from Reebok for certain performance and establishment claims like “Better legs and a better butt with every step” and “It’s the shoe proven to work your hamstrings and calves up to 11% harder and tones your butt up to 28% more than regular sneakers just by walking.”

The NAD determined that a 2008 study commissioned by Reebok did not support the advertiser’s quantified performance claims.

The study included just five subjects who were assigned to wear Reebok’s EasyTone shoes, regular walking shoes, or no shoes at all on an indoor treadmill at a freely chosen pace for five minutes, with electrodes attached to key muscle areas.

“[T]his was a very small scale study both in number of participants and duration of the study,” the NAD noted, adding that a sample size of five participants is not sufficiently “representative of the universe of consumers to whom this product making broad performance claims is targeted. It is well-established that tests offered to support product performance claims must reflect real world conditions. Here, the only testing that was conducted was on a treadmill for a five-minute period of time.”

Although test results for the subjects wearing EasyTone shoes “suggest[ed] the potential” for greater muscle force generation and greater metabolic expenditure, the NAD concluded that such “results that suggest potential toning are insufficient to support unequivocal claims that you will ‘tighten and tone with EasyTone’ and ‘get a better butt.’”

Finding that Reebok’s quantified and general strengthening and toning claims had insufficient support, the NAD recommended that they be discontinued.

In its advertiser’s statement, Reebok said it disagreed with the NAD’s conclusions, but would take the findings into account in future advertising.

To read the NAD’s press release about the case, click here.

Why it matters: “Product testing should reflect consumers’ real world experience to ensure performance claims are meaningful,” the NAD decision reminded advertisers. Advertisers should ensure that their claims can be adequately substantiated with tests that reflect real world conditions. The NAD’s decision comes at an interesting moment for the toning shoe industry, as several recent false advertising class actions have been filed against Reebok’s competitors, like Skechers and New Balance.