Before you can see your abs, you must eliminate your abdominal fat; therefore, low-impact crunches are off the table.

Perform interval training by sprinting all-out for 30 seconds, followed by a minute or so of pacing, and then repeating.

High knees are another high-impact, no-equipment fat-burner that can be performed virtually anywhere.

In training intervals, elevating your legs to your chest for thirty seconds while targeting the same place on the ground with your feet.

Rowing engages both the upper and lower body musculature in a manner that is relatively low-impact on the joints and ligaments.

 The duration of these activities ranges from 20 to 60 minutes, during which your heart rate fluctuates .

One or two HIIT workouts per week can result in a 6 to 15% greater calorie expenditure than steady-state exercise.