What metabolic information can we get from a flat half-marathon?

"I've read that a time trial for 10k or 45 min or 1 hr is a general test for one's anaerobic threshold, and a marathon is raced at one's aerobic threshold. Is that true?"

An image of a solo runner on a rural road
Photo by Isaac Wendland / Unsplash

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I've read that a time trial for 10k or 45 min or 1 hr is a general test for one's anaerobic threshold, and a marathon is raced at one's aerobic threshold. Is that true?

A quick clarification: A given threshold can't be measured with a specific the same event for all people. Without measuring lactate or respiration, duration needs to be used instead of distance.

Non-lab threshold tests are most commonly done with a field test of a given duration. Because the duration of an event a given distance will vary per person, events reveal different things about different people.

For example, a pro-level marathon at ~2 hours would likely be run just above aerobic threshold (AeT.) For any athlete whose aerobic threshold is close to their anaerobic threshold (AnT), that AeT pace wouldn't be sustainable for too much longer than 2-ish hours. (But if they don't have a base, the AnT / AeT gap will be wide, and AeT pace may be slow enough to maintain for much longer.)

So depending on ability and training, a half-marathon can span a wide range of intensities. For a professional, it may be a good proxy for anaerobic threshold; for an amateur (at around two hours), aerobic threshold.

If we assume that a particular runner has a good base (with AnT and AeT thresholds that are ~5% apart,) then:

  • A pro running a half-marathon in the 1-hour range would be running at anaerobic threshold;
  • For someone between 1.5 to 2 hours, the intensity would be between AeT and AnT, similar to a skimo race (although skimo is more stochastic); and
  • Near two hours, the effort would be around AeT (and lower as the duration gets longer.)