To tighten up thigh muscles, one needs to tighten up the hamstring.
Daily stress, standing for long periods, weight lifting will tighten the outer thigh muscles and tendon. One can feel how tight the outer thigh muscles and tendon are by pressing down on the outer thigh with the fingers. If they are tight, pressing on them will cause excruciating pain. If you are standing against a wall and the thigh muscles and tendon are tight, and someone presses the outer thigh, you will feel instantaneously weak in the leg and you will fall. Pressing the outside of the thigh is a major acupressure practice to loosen the sciatic nerve and eliminate sciatica.
One of the more extreme martial arts exercises to strengthen the thigh muscles is to practice the horse stance (ma bu) on the two arms of an arm chair. I used to demonstrate this in my meditation classes. Traditionally, kung fu students and masters would practice the horse stance (ma bu) on top of two wooden poles. One sometimes sees this in kung fu films.