The hip flexors are a group of muscles located in the front of the hip joint. They include the iliopsoas, which is made up of the psoas major and iliacus muscles, as well as the rectus femoris muscle, which is one of the quadriceps muscles.

To perform the advanced motion with ankle weights for your hamstring, follow these steps:

1. Lie down on the ground with your back flat and your legs extended.
2. Lift one leg off the ground and bend it at the knee to form a 90-degree angle. This will be your working leg.
3. If desired, secure an ankle weight around your working leg to add resistance.
4. Engage your core muscles by imagining pulling your navel towards your spine. This will help stabilize your body during the exercise.
5. Begin the motion by lifting your working leg up towards the ceiling, keeping your foot flexed and maintaining the 90-degree angle at the knee.
6. Slowly lower your leg back down to the starting position, maintaining control throughout the movement.
7. Aim for a steady pace, performing 10 to 15 repetitions of the exercise.
8. Focus on activating your glute muscles (your "ass") and maintaining a stable core throughout the exercise.
9. If you experience any pain or discomfort, it's advisable to consult a local family physician or a physiotherapist for proper guidance and assessment.
10. Seeking the expertise of a registered dietitian and athletic therapist can also be beneficial for managing and optimizing your overall condition.

Remember to listen to your body and adjust the weight and intensity of the exercise according to your fitness level and comfort.

The hip flexor stretch you described is indeed a commonly recommended exercise to stretch the quadriceps and hip flexor muscles. It can be done either standing or on the ground, depending on personal preference and comfort.

Here are the steps to perform the stretch:

1. Stand tall or lie on your stomach on the ground.
2. Reach back and grab your ankle with the hand on the same side.
   • If you have difficulty reaching your ankle, you can use a towel or a strap to assist you in grabbing your leg.
3. Gently pull your ankle towards your glutes, keeping your knee pointing downwards.
4. As you pull, you should feel a stretch in the front of your thigh and the hip area.
5. Engage your core muscles by tightening your stomach to stabilize your spine.
6. Hold the stretch for about 20-30 seconds, while maintaining a relaxed breathing pattern.
7. Repeat the stretch on the opposite side if desired.

It's important to note that you should never push yourself to the point of pain or discomfort while stretching. The stretch should be felt as a gentle pulling sensation and should not cause any sharp or intense pain. If you experience pain or have any concerns, it's recommended to consult with a healthcare professional or a physiotherapist for guidance.

In addition to stretching, it's beneficial to incorporate a variety of exercises and movements to promote overall flexibility, strength, and mobility in the hip and surrounding areas. Always listen to your body and modify or adjust exercises as needed to suit your individual needs and abilities.