With 90-minute games, soccer is usually considered an endurance sport. But strength is also key to avoiding injury and improving performance, according to research presented this month at the American College of Sports Medicine’s annual meeting in Minneapolis. Now teams from youth leagues to the World Cup are kicking this science into practice.
When it comes to keeping athletes healthy, “strength training plays a huge role,” says Shawn Arent, an exercise physiologist at Rutgers University who led the work. “You’re really providing the supporting musculature.” He notes robust muscles and tendons stabilize joints, minimizing the risk of a painful twist or tear. His research group partnered with the Rutgers women’s soccer team to add consistent weight lifting to the team’s training regimen. The results were immediate: After one season the team’s injury rate plummeted by 70 percent compared with previous years. Last fall marked the third straight year without a season-ending injury—a rare feat in a sport notorious for torn ligaments and sprained ankles. Arent is now working to publish his findings. “When you can keep your players on the pitch,” he says, “they can accomplish a lot more.”
Upper-body strength could even mitigate a major health concern among soccer players: brain injury from repeated headers, according to Thomas Kaminski, director of the Athletic Training Education Program at the University of Delaware. Kaminski’s own research investigates ways to reduce soccer’s adverse effects on the brain. Frequent headers have been correlated with lower cognitive performance in both amateur and professional players, he says. Kaminski believes a stronger neck and torso can diminish what he calls the “bobblehead effect,” in which a player’s head accelerates rapidly when it strikes a flying soccer ball. That whiplash can damage brain cells. But having more muscle mass in body parts that support the spine and head can reduce acceleration, he says, adding, “It’s simple physics.”
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Kaminski announced plans to test his idea this fall in a youth girls’ soccer league outside of Wilmington, Del. He and his colleagues published a study in 2017 in Research in Sports Medicine that found female youth players suffered greater acceleration from headers than males did. The girls in Kaminski’s upcoming study, ages 11 to 13, will wear sensors that measure cranial acceleration each time they head the ball. The players will also undergo neck- and torso-strength training, which Kaminski hopes will result in decreased acceleration measurements by season’s end. “I’m excited for [this study],” Kaminski says. “This is going to make the game safer,” he claims.
Of course, strength is beneficial for more than just avoiding injury. Strong muscles are also speedy muscles, according to Arent. “A lot of coaches forget: if your player is stronger and more powerful, that means they’re faster,” Arent says. During a slide tackle, arriving to the ball a split-second sooner can mean the difference between a clean steal and a foul (not to mention a jarring collision with an opponent).
Mark Russell, a researcher who specializes in applied exercise physiology at Leeds Trinity University in England and collaborates with Arent, agrees on the importance of strength training for soccer performance. Although endurance matters—players routinely run seven miles in a match—games can be won or lost by how strong players are. “Very often,” Russell says, “the most decisive moments of the game are those high-intensity strength actions.” He notes strength-based movements power 80 percent of goals scored, whether by a leaping header or an all-out sprint to the ball.
Paul Geisler, an exercise and sports science researcher at Ithaca College cautions the goal of strength training in soccer should be more than simply building muscle mass. “If you focus too much on just size,” he says, “you can risk compromising or losing some flexibility and elasticity of those muscles.” To maximize the benefit of strength training, he suggests soccer players focus on “dynamic strengthening.” This method emphasizes muscle extension in addition to contraction—the most common form of strength training. He says players can further reduce injury risk by evening out strength imbalances between opposing muscle groups such as hamstrings and quadriceps. “It’s about coordination and balance,” Geisler notes. “An interrelationship between all those muscles allows the elite soccer player to prevent injury and perform well.”
Arent believes the benefits of strength training extend beyond high-level soccer players. “We’re all athletes,” he says. “We may not all play competitive sports but we were designed to move.” Walkers, joggers and recreational athletes alike can improve performance and reduce injury risk via strength training, he adds. “The lessons that we’ve learned in sports science can absolutely be applied in a much broader sense,” Arent says. “The role of proper training and injury prevention still applies.”
As a former soccer player and “jock who was good at science,” Arent was disappointed at the U.S.’s failure to qualify for this year’s World Cup. Still, he is watching the matches intently. “I’m interested to see which teams are best physically prepared,” he says. He highlighted Germany as a team whose science-based use of strength training and recovery techniques has propelled them into the late stages of recent World Cup tournaments (although they have been eliminated in the 2018 Russian games). “They have always been a very physical team and very at the forefront in terms of their preparation,” he says.
Arent predicts more national teams will follow Germany’s lead in the future. “I expect you’re going to start to see that from more countries,” he says. “They’re going to start appreciating the unique power demands of the sport.”