While it is commonly accepted that exercise provides numerous and wide-ranging beneficial effects, the underlying biochemical changes have remained elusive.  Robert Gerszten, from Massachusetts General Hospital (Massachusetts, USA), and colleagues developed a set of comprehensive plasma metabolite signatures characterizing the metabolic changes associated with exercise.   These pioneers of a new field known as metabolomics, that is -- metabolic profiling, seek to catalog metabolic variabilities among individuals and  identify patterns that may signal risks of disease.  The researchers measured biochemical changes in the blood of a group of healthy middle-aged men and women, some of whom who became short of breath with exertion, as well as marathon runners.  Among the first group, the team identified more than 20 metabolites that change during exercise, some of which were not previously known to be involved with exercise.   Among the marathon runners in the study, the researchers observed a ten-fold increase in the metabolite niacinamide, a nutrient byproduct involved in blood-sugar control.  In analyzing the collective data, the researchers determined that ten minutes of exercise has at least an hour of effects on the body.