Early in my judo career I couldn’t do uchi mata to save my life. I have relatively long legs, I’m just about 182 cm (pretty much 6’0″), so it should have been a bread-and-butter throw. Tanner had no problems with it. He would just grab and before I knew it I was on the ground.
The variation I first learned was what I consider “traditional”. You throw facing forward, your leg lifts up making contact along theirs more or less the whole length of the leg, and it’s the hand pull and twisting of your hips that finishes it. Later I’d learn that the reason it wasn’t working is that I didn’t have uke’s arm pulled out in front of me enough. I also learned how hard it was to get that much pull for me because even to the limit of what I’m physically able to do, it’s not as much pull as the coral belt who was teaching at the time wanted. If I’m in just the right configuration and the person has committed themselves forward already, I might hit it. Maybe.
The second variation I learned didn’t work any better. It’s the “hip version”. It looks about the same, but you actually attack the opposite leg – making thigh to thigh contact on the far leg for the lift – and then cut across to the nearside leg during the finish to cause the rotation. I can kind of fake this one by starting with a hane goshi and then cutting the leg across once they’re lifted, but I still am not quite sure what detail I’m missing that would make this one work the way it’s supposed to. Play with it as I may, only in a kata setting have I ever been able to hit it.
The third variation, which I hadn’t learned until only a couple years ago, is a lower uchi mata. You make ankle to ankle contact rather than whole leg contact, and are facing more toward uke rather than the same direction. I’d describe the action as an ankle pick with your leg – pulling to the rear outside corner instead of the forward outside corner to finish. This quickly became a staple throw of mine. It just works for me. Even if uke has shorter legs so I can’t get low enough to get my leg in, being able to pop theirs up usually lets me do some throw. Having said that, I’ve tried to show it to others, and they still prefer one of the other variants.
Personal preferences and slight variations in the application of a technique are important. The core set of techniques work, but sometimes finding the right variant of a given technique is what’s really necessary to turn it from hot garbage into a staple. Everyone has some variant on the notion that you can ask four black belts how to do one technique and get six different answers. If you feel like you just absolutely suck at a technique, but you want to do it better, it may be worth a try to see if there’s a different variation you can use instead.