I've just recently begun training again for sport taekwondo - specifically sparring. I've always had a more traditional training, but these days the front-leg heavy style is what's in vogue and I have trouble against them. What are some good ways to break through the defense of the leading leg? I'm told that the regular approach is to beat them in playing the front leg game, and then follow with a good offensive mix-up. The problem is that if you manage to block or get past the first kick, the second one is coming straight for your head. In addition, the front leg has better reach and less committal than a back leg kick, so it's difficult to punish/counter.
I would watch people specifically in your division. Heavyweight games are much different than fin or fly weight fights. Even male/female fin weight divisions fight different. Watch what people are doing in your specific division.
Keep an eye out for Phil's section on this. (USA National Team member, Phillip Yun, is going to run a section on this soon. https://www.youtube.com/user/itsenzothephillip)
Currently I run two schools of thought on this. (I am smaller than average for my division). 1) To make a grab/throw against the leg. If you can get your hands on footage from Daehoon Lee in the 2014 Asian games, it's a perfect example, except in my case, I go with a back kick or hook kick instead of the roundhouse counters to the face.
Another example is to watch the Russian Flyweight in the Russia World Championships 2015. He was really good at getting around the front leg of all of his opponents, using his punch and his body. Off the top of my head those are the best two examples I can see.
The next school of thought is to go fencing with them. This is all fairly new, but the cutkicks can either go low, medium or high. If they're low, we're being taught to cut ontop of their legs and bring it to the body or face (flippy kicks). If it's high, we usually swing our leg up, straight into theirs to try and displace their balance and then follow up as they're recovering. Another option is to do a front leg hook or a reverse kick under their leg. (I'm not flexible so this isn't as effective for me). Also I've seen front leg in out axe kick do well. If it's in the middle, you have to gauge the distance and how bent their leg is, you can do any of the options presented above. The game is fairly new. The key right now is to find what works for you and to get really good at it.
The sport and its dynamics have changed greatly and it seems the UZB heavyweight and many of the IRI national team players have figured it out. I'd suggest watching their gameplay and see what you like.
Something Dr. Jason Han told me a long time ago was to try everything and keep what worked for you. I think it's applicable now. Good luck in your next matches!
You can watch other people sparring to see how they deal with front-leg kicks; either watch 'live' at tournaments, or search for videos on YouTube. However, I watched a video of a gold medal final from the London Olympics and couldn't really see what their approach was!
I train in ITF TKD, which normally has a different approach to sparring (more use of hands, for one thing!). One of the ways we use to get round front-leg attacks is to step closer to the attacker (have a look at this video) or step sideways, rather than backwards
I know from personal experience that it is much, much easier to say/type that than it is to actually do (I certainly spend more time going backwards when I spar!)
Something you may notice from the second video is a spinning kick as a counter to the front-leg attack. In ITF TKD, the back is not a target zone, so strikes to the back do not count (however uncomfortable!); the spin moves your target area away from your opponent and gets your foot closer to their target area. It is also quite an intimidating technique, which can be useful.
Lastly, you can always ask the people you train with how they deal with front-leg attacks!