The New York Times – “When we exercise, the levels of thousands of substances in our bloodstream rise and drop, according to an eye-opening new study of the immediate, interior impacts of working out. The study is the most comprehensive cataloging to date of the molecular changes that occur during and after exercise and underscores how consequential activity — and inactivity — may be for our bodies and health….But for the new study, which was published in May in Cell, scientists at Stanford University and other institutions decided to try to complete a full census of almost every molecule that changes when we work out….They wound up measuring the levels of 17,662 different molecules. Of these, 9,815 — or more than half — changed after exercise, compared to their levels before the workout. Some increased. Others declined. Some gushed immediately after the exercise, then fell away, while others lingered in heightened or lowered amounts for an hour after the workout. The types of molecules also ranged widely, with some involved in fueling and metabolism, others in immune response, tissue repair or appetite. And within those categories, molecular levels coursed and changed during the hour. Molecules likely to increase inflammation surged early, then dropped, for instance, replaced by others likely to help reduce inflammation.

“It was like a symphony,” says Michael Snyder, the chair of the genetics department at Stanford University and senior author of the study. “First you have the brass section coming in, then the strings, then all the sections joining in….”