If you love running take up jogging. There is no need to go flat-out, just jog at a relaxed speed using proper shoes and on level ground. It won’t be long before you notice a visible difference in your thigh muscles growing bigger and the fat slowly melting away.
Cycling is another activity that tones up the thighs. Your thighs get a great workout when you cycle long distances. The sense of freedom and happiness that you feel when cycling is not matched by other exercises.