I think the problem started with a bad bike fit on my tri bike and developed tightness (starting on tendonitis) at the top of my quads, in the hip/groin region. The standard one legged quad stretch is good, but doesn't isolate the top part.. the lie on your stomach and stretch the quad behind is better, but still didn't isolate the right part. The kneeling quad stretch is better again as it engages the top of the quad when pushing the hip forward.. but takes some balance and the majority of ones body weight is supported on the knee which is being stretched.. ouch!
Here it is - stand next to a cushioned chair with the seat very slightly below knee height, then just do the one legged quad stretch with your knee resting on the seat. With a combination of pushing your hip forward and slightly bending your straight leg you can isolate any part of the quad you want while staying balanced and not stressing any other part of the body.
I do it at work all the time now.. standing at my desk while pretending to read something
