Lie flat on back. Bend left knee at 90-degree angle, keeping foot flat on floor. Keeping the right leg straight, slowly lift it to the height of the left knee. Hold for a count of 3. Repeat 10 times. Switch sides. Work up to 10 sets of 10 over several weeks. Safety Tip: Lifting both legs at the same time causes excessive stress on your lower back so only lift one leg at a time; the opposite leg should be kept slightly bent with foot on floor.