Jill Biden Surprises L.A. Spin Enthusiasts, Drops into SoulCycle Class

Jill Biden isn't pumping the brakes on her SoulCycle obsession anytime soon -- surprising spin enthusiasts in L.A. by dropping into an early morning class for those much-needed endorphins.

Sources tell TMZ the First Lady's suited and booted Secret Service agents arrived first to the trendy cycling chain's 7 AM class in Brentwood earlier this month ... wanding down everyone and informing them a VIP would be in class.

Upon entering, Jill settled onto bike no. 42 -- at the back, right by the Secret Service team at the entrance ... just in case she needed to make a speedy escape.

There was no theme for this SC class, though we're told at one point they rode to Janet Jackson's "Escapade" ... and Jill was, noticeably, in great shape.

She even appeared to make a friend ... fist-bumping a boy riding in front of her at the end of class, but there were no photos due to SC's no-phones-in-studio policy.

Jill attended the class in the middle of a jam-packed weekend of fundraising events with President Biden -- probably hoping for some me-time, as she's previously credited the spin classes for helping her find her "inner strength so she can be strong for everyone else."