The goal, said Dr. George Chiampas, the chief medical officer for the federation, is to educate players with real-time information about their health and nutrition in the hope “that the more they know about themselves, the more engaged and committed they’re going to be on their side.”
Change within soccer can still be met with suspicion, however, and even resistance. Only recently, for example, has the game begun to employ instant replay technologies that have long been used in other sports. But soccer has more eagerly embraced other areas of data-driven sports science.
Player movement is seemingly tracked by every device but bloodhounds, like heart rate monitors, GPS units, accelerometers and gyroscopes. In preparation for a World Cup qualifying match at an altitude of 7,300 feet last month in Mexico City, members of the men’s national team drank beet juice (a blood-flow enhancer) and tart cherry juice (a sleep enhancer) and took supplemental iron to increase production of oxygen-carrying red blood cells.
And as part of a long-term health and performance strategy, the team’s medical staff and players have begun to examine everything from bone health to triglycerides.
Participation in the blood analysis is voluntary, Chiampas said, adding that the program adheres to privacy laws protecting the confidentiality of players’ health care information. If, as planned, U.S. Soccer extends the program to its youth national teams, parental consent will be sought for players younger than 18, he said.
“We don’t mandate that anybody do anything,” Chiampas said.
Chiampas said more research is needed into the efficacy of micronutrients — vitamins and minerals needed in trace amounts — in improving performance. And the United States Anti-Doping Agency has long cautioned athletes that the supplement business is loosely regulated and that product labels can be “notoriously unreliable.”
It is difficult, too, to quantify how this blood analysis could help the United States reach the 2018 World Cup and advance beyond the first or second round of the tournament next summer in Russia.
“The science in sports has grown tremendously,” said Bruce Arena, the coach of the men’s national team. “You know everything you need to know about a person. Whether it makes them any better or not is up for debate.”
But at least one other prominent sports team, the Golden State Warriors, the winners of two of the last three N.B.A. titles, also uses a version of the blood analysis/supplement program of Thorne Research and its affiliate, Wellness FX.
Chelsea Lane, the Warriors’ director of performance and sports medicine, said in an email that she admonished players for whom “every 1 percent counts in the pursuit of excellence.”
In the past, nutritionists spoke to the players on the national team as a group and gave comprehensive advice about balanced diets, U.S. Soccer officials said. Now the team has taken a more personalized approach.
At a training camp in January, players’ blood was drawn and analyzed. Their individual results were retrieved via a mobile app, and consultations were available with the team medical staff and health experts of Wellness FX, which conducted the blood chemistry analysis.
The results are a biological passport that, with the athlete’s approval, the national team can share with each player’s club team.
“For each player to have their individualized results and to be able to target different areas they need to work on is really important because everyone is so different,” said Morris, whose club team, the Seattle Sounders of Major League Soccer, has its own sports science and performance manager.
Morris, 22, said he had begun taking more vitamin D (for calcium absorption and strong bones) and iron (for red blood cell production). And for Morris, monitoring of his blood sugar levels is vitally important; he was found to have Type 1 diabetes when he was 9 and wears a glucose monitor and an insulin pump.
Clint Dempsey, a teammate of Morris’s with the Sounders, tied Landon Donovan’s record of 57 goals for the national team with a curling free kick on Saturday in the Gold Cup semifinals. But Dempsey is also 34 and missed the final four months of the 2016 M.L.S. season with an irregular heartbeat.
He has had blood screening with Seattle and the national team. He said he had augmented his diet with magnesium, which can help normalize heart rhythm; glucosamine for his joints; fish oil for cardiovascular health; and multivitamins.
“People are just trying to figure out ways to get that edge to be at their best and prolong their careers,” Dempsey said after the quarterfinals. “It’s recovery, taking care of your body, sometimes seeing a chiropractor, sometimes getting acupuncture. You’ve got to figure out ways to be on the field. The older you get, the harder that gets.”