This is one of my favorite stretches for the hip flexors. Start by getting into a lunge position with your front knee at a 90-degree angle and your back knee on the ground. Next, engage your core by pressing forward on your hip flexion and tuck your pelvis under at the same time. Hold for 30 seconds.
A couple of good stretches for them, you want to lengthen not only the hip flexor but quadriceps. So the front of your thigh. There’s a lunge stretch that we teach here, two ways to do it really. One is from a kneeling position and one is from a standing position and eventually progressions to maybe one on one foot as well.
Make sure that your kneecap is directly over top of your ankle so that knee doesn’t collapse in or out. That’s important for stress on the knee joint. So you would lunge forward and then straighten your back leg till you feel mild discomfort or tightness in the front and then relax. Or hold wherever you’re comfortable. And again, not to feel pain or anything like that, just stretch it and kind of get used to it and hold there and breathe normally and eventually progress forward with more repetitions or more intensity