Peloton has warned parents to keep children away from its treadmills after the death of a child.
Boss John Foley said the firm recently learned of the “tragic accident”, one of a “small handful” of incidents in which children have been hurt on its exercise equipment.
He did not provide further detail about how the accident happened.
But he said children should stay away from the firm’s machines, which surged in popularity during the pandemic.
“We design and build all of our products with safety in mind. But in order to help ensure that you and your family members stay safe with Peloton products in your home, we need your help,” he wrote in the letter to customers.
“Keep children and pets away from Peloton exercise equipment at all times. Before you begin a workout, double check to make sure that the space around your Peloton exercise equipment is clear.”
Peloton sells cycling machines and treadmills that can be connected online to virtual fitness classes. Its business has boomed as people look for alternative ways to exercise during lockdowns and gym closures.
The firm has said the skyrocketing demand has created supply chain pressures, leading to backlogs in orders for the machines.
Its treadmills, which sell for more than $2,400 (£1,722), were designed for use by those aged 16 and older, who weigh at least 105 pounds, it said.
Mr Foley said the company did not intend to release more information about the accidents, in order to respect privacy of those involved.
“While we are aware of only a small handful of incidents involving the Tread+ where children have been hurt, each one is devastating to all of us at Peloton, and our hearts go out to the families involved,” he wrote.
The company is “currently assessing ways to reinforce our warnings about these critical safety precautions to hopefully prevent future accidents,” he added.
Last year, Peloton recalled about 27,000 bikes in the US, citing problems after clip-on pedals broke unexpectedly during use.