Stanford study raises prospect of blood test to measure aerobic fitness
An impressively comprehensive new study from Stanford University has delivered the most thorough investigation into the human body’s molecular response to exercise ever conducted. The research chronicles in detail how a single session of aerobic exercise triggers broad systemic molecular changes, and the findings point to a potential future blood test that could objectively measure a person’s general fitness.
"Everybody knows exercise is good for you, but we really don't know what drives that at a molecular level," explains Michael Snyder, co-senior author on the new study. "Our goal at the outset was to conduct a highly comprehensive analysis of what's happening in the body just after exercising."
The best general test currently available to measure a person’s aerobic fitness is called a peak VO2 test. This involves a subject running on a treadmill, with progressively increasing intensity, while oxygen consumption is measured through a mask. A VO2 max measurement is reached when an individual’s oxygen consumption peaks at a steady level regardless of increases in exercise intensity.
The Stanford study recruited 36 subjects, aged between 40 and 75, with varying levels of insulin resistance. The subjects then performed a traditional peak VO2 test, with blood samples taken before and after the exercise test.
Instead of taking just one blood sample following the peak VO2 test, the researchers gathered four post-exercise blood samples – at two, 15, 30, and 60 minutes after the session. This allowed the researchers to study molecular changes from an unprecedented temporal perspective.
"All of these measurements allow us to describe a choreography of molecular events that occur after physical exercise," says Snyder. "We know that exercise causes an array of physiological responses, such as inflammation, metabolism and hormone fluctuation, but these measurements allowed us to characterize those changes in unprecedented detail."
Unsurprisingly, the researchers detected intense molecular responses two minutes after the subjects finished exercising. A variety of metabolic and immune biomarkers spiked immediately, however, rapid changes over time were detected. The two-minute test revealed the subjects metabolizing amino acids for energy, but this had shifted to metabolizing glucose by the 15-minute mark.
"The body breaks down glycogen as part of its exercise recovery response, so that's why we see that spike a little later," explains Snyder.
Those subjects with pre-existing insulin resistance displayed different post-exercise molecular activity. Snyder notes these subjects generally showed a dampened immune response immediately following exercise.
Perhaps one of the more immediately pragmatic outcomes from the robust research is the suggestion a simple blood test could replace the traditional peak VO2 test as a way to objectively test a person’s fitness. The study did identify a clear correlation between the subjects’ baseline blood tests and their subsequent peak VO2 results.
This correlation suggests the same aerobic fitness data collected by a peak VO2 test could be gathered from a blood sample. The problem the researchers will need to overcome will be finding a way to simplify the test and find a small sub-set of molecular biomarkers that are representative of the peak VO2 data.
The current test used in this study was incredibly expansive, analyzing thousands of different molecular biomarkers. Obviously this would not be feasible for a common clinical test, but the researchers are currently developing an algorithm to sift through the mass of data collected and home in on a few particular molecular biomarkers that are most correlative of the peak VO2 data.
"Aerobic fitness is one of the best measures of longevity, so a simple blood test that can provide that information would be valuable to personal health monitoring,” says Kévin Contrepois, co-lead author on the study.
The new research was published in the journal Cell.
Source: Stanford Medicine