And clear patterns emerged. The researchers found that levels of 147 proteins were strongly linked to people's basic fitness. If some of these protein counts were high and some were low, the resulting molecular profiles showed how fit someone was.
Even more intriguing, a separate set of 102 proteins tended to predict people's physical responses to exercise. Higher and lower concentrations of these molecules – few of which overlapped with the proteins associated with basic human fitness – prophesied the extent to which a person's aerobic capacity would increase, if at all, through exercise.
Because aerobic fitness is so closely linked to longevity, the scientists eventually checked the levels of the various fitness-related proteins in the blood of people who took part in a separate health study that also included mortality records and found that protein signatures had a lower or lower level Implying greater fitness response also meant shorter or longer life.
Overall, the results of the new study suggest that "molecular profiling tools could help tailor training plans," said Dr. Robert Gerszten, professor of medicine at Harvard Medical School and chief physician for cardiovascular medicine at Beth Israel Deaconess Medical Center, led the new study with lead author Dr. Jeremy Robbins and others.
Someone whose blood protein signature suggests that he or she might gain little fitness from doing normal, moderate walking, cycling, or swimming, for example, might be pushed into more vigorous workouts or resistance training, said Dr. Gerszten.
However, this area of research is still in its infancy, said he and Dr. Robbins. Scientists will need to study far more people, with far greater differences in health, fitness, age, and lifestyle, to determine which proteins are most important in predicting a person's exercise response. The researchers also hope to trace back and find out where these molecules originated to better understand how exercise reshapes our bodies and reshapes our health. Expect more and more refined results within a few years, said Dr. Gerszten.