a fit human can store enough sugar to run nearly fifteen miles. But there is a consequential catch: during glycolysis the leftover halves of each sugar, molecules known as pyruvates, accumulate faster than cells can handle. As pyruvates pile up to intolerable levels, enzymes convert each pyruvate into a molecule called lactate along with a hydrogen ion (H+). Although lactate is harmless and eventually used to recharge ATPs, those hydrogen ions make muscle cells increasingly acidic, causing fatigue, pain, and decreased function.21 Within about thirty seconds, a sprinter’s legs feel as if they
...more
