Walmart US CEO Greg Foran asked workers to email him their biggest complaints about where Walmart "cut muscle instead of fat," and his inbox was flooded with 2,700 responses.

Workers most commonly complained about Walmart's removal of toilet-seat covers from restrooms, he said.

"Small thing, but really important," Foran said. "In the interest of saving money, we'd taken those things out."

Walmart US CEO Greg Foran stood on a stage at a company holiday meeting five years ago and asked thousands of workers to email him.

"Can you send me three things where you think we've cut muscle instead of fat, and can you email it to me?'" Foran recalled asking, recounting the incident at a recent UBS conference. "Immediately, I could feel the emails coming in. I ended up getting about 2,700 emails."

A surprising theme emerged from the thousands of responses that flooded his inbox: Workers wanted toilet-seat covers returned to the stores' restrooms.

"Small thing, but really important," Foran said. "In the interest of saving money, we'd taken those things out."

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At the time, Foran had recently been appointed CEO of Walmart's US business. He was trying to execute a turnaround following two years of quarterly same-store-sales declines.

He said he discovered that returning the toilet-seat covers and fixing other "hygiene factors" were vital to getting employees involved in the turnaround plan.

"I've learned something over the years: You can never motivate anyone until you fix some of these factors," he said.

He said that for the first year it was about fixing those and saying: "What are the things that you need? OK, you need the electrician to get that plug fixed? Get it done. You need that restroom remodeled? Get it done."

"Then people start to buy into it," he said.

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These investments gave workers "a reason to believe," which is critical when you're trying to motivate a workforce of 1.2 million people, he said. Walmart's quarterly same-store sales turned positive shortly after Foran took over, and they have been growing for four years.

Stores now have the tools they need, he said, so the company is "raising the bar" in terms of performance.

"I know when I now visit not just stores but distribution centers, and I talk to our associates and I talk to our leaders ... the conversation is 'Actually, you've given us what we need — now we've got to get on and execute.'"