(ABC News)

Maybe he was having a hard time getting to 10,000 steps.

Sen. Chuck Schumer, D-N.Y. is warning against fitness trackers such as FitBit, citing privacy concerns.

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Schumer has called on the Federal Trade Commission to regulate the massive quantity of data tracked by wearable fitness devices.

"Personal fitness bracelets and the data they collect on your health, sleep, and location, should be just that - personal," Schumer said in a statement on Sunday.

"The fact that private health data - rich enough to identify the user's gait - is being gathered by applications like FitBit and can then be sold to third-parties without the user's consent is a true privacy nightmare," Schumer said.

FitBit stores data on users' walking, exercise and sleep habits, encouraging users to reach activity benchmarks, such as 10,000 steps per day. The San Francisco-based company claims its users "take 43% more steps with FitBit."

A representative for FitBit told Business Insider the company is "committed to our users' privacy and [welcomes] the opportunity to work with Senator Schumer on this important issue."