Credit: Steve Granitz/

New year, new fitness plan for Jessica Simpson.

The singer and VH1 reality star, 29, posted on Twitter earlier this week, "Just got done boxing.

"Second day in a row... Have I lost my marbles?" she added.

Relive Jessica Simpson's most controversial moments

The curvy singer -- who next appears in "The Price of Beauty" -- has been chronicling her gym routine on Twitter.

Can you spot Jessica Simpson's lips in this photo gallery?

"Why am I still hurting from our workout earlier? I'm getting old!" she wrote last November, adding that she has "sore buns."