While the 800/1600 won’t be as specific as the 100/200, she won’t lose that much. It will be more of an execution thing…any “trouble” she has going back to racing the 100/200 will only be getting used to that distance. And, at the end of the day, she’s 14! Diversity of training is critical for fun and to identify where, in fact, she naturally excels. Good luck to her!

From a tri perspective, you have to really think about WHY you want to train fast twitch fibers. Since even our shortest races take elite folks an hour (sprint tris), the effectiveness of fast twitch fibers is reduced over that timeframe. I think fast twitch work plays a very strong role in tri technique / execution, however, regardless of the overall race distance. I recommend folks include spin ups (to max cadence and hold for 1 min) on the bike in the base training phase and 1- to 3-min bursts / accelerations in the tapering phase. From a running perspective, high turnover efforts are good, as is including strides (30-seconds fast, jog back recovery) at the end of long slow runs is also effective.

Explosive weight training is another way to target FT muscles…but most folks don’t have the proper technique to execute these…so I won’t really get into that here.

Good luck!

-Thanks, Jameson