If you’ve been around a while, then you’re familiar with The Oxygen Challenge series — an all-encompassing and comprehensive fitness and nutrition plan that will help you achieve your goals, no matter what your current level of fitness. Now in its fourth year, the Challenge is better than ever, and it will help you change your body, your life, your mindset and your attitude.

This year, we’ve enlisted two of television’s most celebrated fitness and movement experts — women who have led others to achieve goals they never thought were possible — Jen Widerstrom and Karina Smirnoff. Each has created her own unique 90-day program exclusively for Oxygen that will get you into the best mental and physical shape of your life.

Jen Widerstrom is best known for her role as a transformation expert on NBC’s The Biggest Loser, and she is now bringing her depth of knowledge and transformative expertise to the Oxygen audience. Her plan uses simple tools — dumbbells and a medicine ball — making it accessible to everyone and doable anywhere. Through continual adaptation and progression, coach Jen’s plan moves you forward toward your goals, no matter your starting point or skill set.

Karina Smirnoff is a professional ballroom dancer, and though she is best known as one of the coaches on ABC's Dancing With the Stars, she has also created several successful fitness DVDs that have helped millions lose weight and have fun doing it. Coach Karina uses dance as a foundation for her programming, blending it with power, strength, yoga and even self-defense. Not a dancer? Not to worry: Coach Karina breaks down all her dance steps in detail so that even those with two left feet can cha-cha and salsa like a pro.

No matter which coach you choose, the plans work like this: Each day for 90 days, you will receive exclusive video content from your coach. She will personally take you step by step through the workout of the day, offering form tips, modifications for special populations and intensifiers for more advanced athletes. This enables you to tailor the program to suit your own purpose and level of conditioning. You’ll also gain access to a nutritional plan that outlines your coach’s theory on food, offers guidelines for meal prep, provides detailed grocery lists and delivers coach-approved recipes, making getting in shape easy as well as delicious.

With the help of coach Jen and coach Karina, you will get into the best shape of your life and have fun doing it. OC4 gives you all the tools you need to make lasting changes to your physique and your lifestyle.

So what are you waiting for? Sign up today. You’re only three months away from becoming your best self, ever!