Final answer:
You can feel the tensor fasciae latae contract by asking a supine partner to perform hip flexion or thigh abduction, which involves lifting the leg upward or moving it away from the body's midline.
Step-by-step explanation:
To feel the tensor fasciae latae contract when your partner is laying supine, you can ask them to perform the action of hip flexion or abduction. The tensor fascia latae is a muscle that helps in flexing and abducting the thigh due to its position in the superior aspect of the lateral thigh. It also plays a role in stabilizing the knee by maintaining the tension of the iliotibial tract. To palpate this muscle's contraction, you might ask your partner to lift their straight leg upward off the ground (hip flexion), or move their leg away from the midline of their body (abducting the thigh), while keeping the knee straight.