Why Can’t I Run Faster?

Contrary to the outdated locker-room myth, the reason you hit your limits is not simply that lactic acid is scorching your muscles. Instead, the sensations you feel while running each correspond to a different minicrisis in your body, and they combine to determine whether you can hold your pace.

Last spring, scientists from around the world gathered in San Diego for a special conference to share the latest results in their search for the ultimate limits of endurance. They discussed hot new topics like metabolites and mental fatigue, as well as the familiar foes like heat and hydration. Here is what their findings reveal about what’s behind the pain of pushing for a PR.

“I CAN’T CATCH MY BREATH!”
Cause: Oxygen deficit
Occurrence: Shortly after starting to run
Antidote: A “priming” warmup, including a sustained burst of intense running

“I’M RUNNING HARDER, BUT I’M NOT SPEEDING UP!”
Cause: Inefficient muscle-fiber recruitment
Occurrence: Sustained medium efforts like 10K to half marathon
Antidote: Train your fast-twitch fibers to be more efficient.

“MY LEGS ARE ON FIRE!”
Cause: Metabolite accumulation in your muscles triggers signals to your brain.
Occurrence: Mile or 5K races, fast surges, or finishing sprints
Antidote: Short, fast interval workouts

“I GIVE UP!”
Cause: Effort overload
Occurrence: Anytime you’re pushing your limits
Antidote: Train your brain.

Click read more for other barriers and more about the antidotes for those listed above.