Extreme events reveal an alimentary limit on sustained maximal human energy expenditure.
Level 4 - case-series / case-control
Prospective observational cohort combined with compiled historical observational datasets
PubMed 31183404 · doi:10.1126/sciadv.aaw0341
What was done
Researchers evaluated maximum sustained metabolic scope (SusMS) relative to basal metabolic rate (BMR) across human endurance events lasting 0.5 to 250+ days. They compiled total energy expenditure (TEE) and BMR data from endurance and overfeeding literature and added new prospective data from adults running ~250 km/week for 20 weeks in a transcontinental race.
What was found
SusMS decreased curvilinearly with event duration, plateauing below 3× BMR. Incorporating overfeeding data indicated an alimentary energy supply limit of ~2.5× BMR; expenditures above this required drawing down body energy stores. Transcontinental race data showed humans partially reduced TEE during long events to extend endurance.
Why it matters
This study defines a digestive and metabolic limit on sustained human energy throughput (~2.5× BMR), clarifying biological constraints on extreme endurance, heavy occupational labor, and reproduction.
Limits
The abstract reports no sample size (n), participant demographics, or variance metrics. The findings rely on extreme endurance athletes and compiled historical cohorts, which may limit generalizability.
Cited by
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