Witherspoon's Upside Down Workout

Reese Witherspoon gets down and dirty for a workout in Santa Monica on Thursday.

The Oscar-winning actress was worked hard by her personal trainer — running, doing ab exercises and working out her upper body with handstands. Reese, 31, kept track of all of her exercise experiences in a BodyMinder exercise journal.

In fashion news, Reese has been offering her advice to Nina Ricci Artistic Director, Olivier Theyskens.

Theyskens says, “My best friend Reese has helped me design [the latest collection] – she is always giving me materials and advising me.”

An insider tells Glamour, “Olivier and Reese herself love the combination of the brand and her style.”

15+ pictures inside of Reese exercising up a storm…