The Sport Information Resource Centre
The Sport Information Resource Centre

As extreme endurance races become more popular, athletes are confronting a new limit on human performance – their gut. New research shows your digestive track can only absorb 2.5 times your basal metabolic rate (BMR) worth of calories per day. With some athletes depleting their glycogen and fat stores at 4 or 5 times their BMR during each day of competition, performance will eventually be affected because they can’t absorb enough nutrients to refuel their bodies.