Strength comes from resistance. Body builders and weightlifters spend many hours in strength training, but their muscles are not as flexible as dancers. This is because when they are developing their muscles, they usually do quick short movements to make them lean and compact. As a dancer, however, you have a need to strengthen muscles more than develop them. So we pair our strength training with flexibility, and alternate fast and slow movements to maximize our movements.

Choose a space that will allow you to walk unhindered for a few feet. The longer the better, but a short space will do. Now, shifting your balance to one leg, slowly lift the other from your hip, as high as you can control, and bring it down  with the same slow control you used to lift it. Gravity is providing the resistance you need to develop strength, the lift is both lengthening your muscles and helping to increase flexibility. Do this across the floor a few times a day, taking care to control your leg as it comes down, and lifting it as high as you can in a slow controlled manner as it goes up.