Want to run faster off the bike? Stop training like a runner and start training for a single sport: triathlon. Durability is the biggest limiter to triathlon run speed. Additional run mileage is not the secret to a successful triathlon run performance. Athletes looking to run faster off the bike need to run the right type of volume to build appropriate multisport resilience and durability.
Your triathlon resilience & durability is developed week after week, month after month & year after year. Sound boring? It is. Swim fitness is bike fitness and bike fitness is run fitness.
Regardless of the race distance, you will feel the effects of limited swim & bike volume on your run. As events get longer, the lack of durability across all three sports will emerge. Afterall, you can't ride at race pace if you're exhausted from the swim. Riding at race pace on an overly fatigued body will lead to an underwhelming run performance.
Consequently, you don’t just run more miles to get faster at running off of the bike. In fact, in-season weekly run mileage should never really be more than 1/5 of your bike mileage.
Assuming that you pace the bike properly and there are no nutrition limiters, your open vs triathlon run times should not decouple more than 6% (70.3) and 12% (IRONMAN). For example, if your open half marathon time is 1:30, you shouldn’t run slower than 1:36 off the bike. If your decoupling is greater than 6%, focus on your swim & bike volume before you reevaluate your run volume.
A coach should work with every athlete individually to apply the right stimulus to raise their V02 ceiling, build durability and give that athlete more room to increase aerobic output. An easy way to do this is to make their easy sessions easier and their hard sessions harder. A clear contrast in intensities will prevent plateauing, increase performance adaptation and build durability: the foundation of triathlon run success.