How the body recovers from an ultramarathon

Ultramarathons -- footraces longer than the traditional 26.2-mile marathon -- have grown in popularity, with some people participating in multiple races each year. These races most often take place on tracks, roads and trails with terrains and environmental conditions that challenge even the most seasoned runners.

"The exponential increase in the number of people running multiple ultramarathons each year, combined with the physical stress each race places on a runner's body, has made it important to understand the factors that enhance recovery," explains Joseph Chin, a second year medical student at SUNY Upstate Medical University. Chin served as a summer extern at the VA Northern California Healthcare System and member of the research team under the mentorship of the Principal Investigator, Martin Hoffman, MD; chief of PM&R at VA Northern California Health Care System and professor of PM&R at the University of California Davis. The team studied 72 participants in the 2015 Western States Endurance Run -- a 100-mile trail race through the Sierra Nevada mountains of Northern California where runners climb 18,000 feet and descend 23,000 feet.

The team first established each participant's baseline function with two separate 400-meter runs in the 21 days prior to the race, and this was repeated at days three and five after the race. The researchers also assessed subjective measures by participant's lower body muscle pain -- on a scale of zero (no pain) to 10 (unbearable pain) -- and fatigue at race registration, immediately after the race, and each morning for the seven days immediately following the race. Finally, at completion of the race, the researchers collected blood samples from participants to determine plasma creatine kinase concentrations of each runner, which measures muscle damage.

While assessing the outcomes of these tests, the researchers also took into account other factors that might affect a person's recovery. "Ultramarathons are challenging runs, and we expected a number of factors to affect recovery," says Chin.

"In this study, we looked at those factors that seem to be the most important and most easily obtained; these included age, sex, race finish time, number of years of regular running, number of years running ultramarathons, number of 100-mile marathons completed, number of 100-mile ultramarathons started, average weekly running distance, highest week running distance, and longest training run or race during the three months prior to the Western States Endurance Run."

Instead of the typical 24 to 72 hours it takes to recover from exercise-associated muscle pain and soreness, the participants required an average of five days to recover. This -- according to Mr. Chin -- is to be expected from such a physically demanding sport. However, despite recovery from pain and fatigue, speed does not return to baseline within that time frame.

The researchers noted that older runners reported slightly less muscle pain and soreness. Also, higher levels of post-race plasma creatine kinase concentrations were correlated with higher muscle pain and soreness ratings. However, Chin notes the muscle pain, soreness, fatigue, and change in run times are not good indicators of severe muscle injury (called rhabdomyolysis), and blood tests are best to capture this information.