Try this knee-friendly 35-minute workout, requiring no equipment, designed to burn calories and build strength safely.

HIIT workouts don't have to include burpees and jumping jacks and jump squats. In fact, you can get in a totally effective low-impact workout that's still high intensity and burns major calories.

While sit-ups and crunches might be seen as the cornerstone of ab and core workouts, they’re far from the only moves that get results. Plenty of other exercises take you off the mat and onto your feet ...