Cast of

Tone & Shred: HIIT and Core with Karena, Katrina and Jillian

Tone & Shred is the first collaboration between Jillian Michaels and Tone It Up exclusively for FitFusion. in Tone & Shred: HIIT and Core, this 25-minute workout combines techniques from the most popular and powerful fitness modalities - HIIT, Yoga, Pilates, dynamic resistance training and more to ensure incredible variety, maximum results and a sweat session you'll like showing up for!