<human>:  What’s the best way to improve muscle mass in a teenagers thighs?
<bot>: The best way to improve muscle mass in a teenager's thighs is to focus on compound exercises like squats and lunges that target the thigh muscles. High intensity interval training and plyometric exercises can also be added to the mix to quickly build leg strength and power. Additionally, incorporating proper nutrition with a balanced diet and adequate protein intake is essential for building lean muscle tissue.