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Specific mechanisms remain unclear
Multimodal warm-up exercise programs appear to have benefits for reducing the incidence of groin injuries in athletes, but researchers are working to identify which specific training components have the greatest effect.
Almost an afterthought at the 2008 sports injury prevention congress in Tromso, the topic of groin injury prevention was deemed worthy of a three-hour symposium in Monaco just three years later. Presenters from Copenhagen and Santa Monica, CA, reported on the results of two similarly conceived exercise prevention programs implemented in elite soccer players.
“We need to address dynamic stability and address faulty biomechanics of the pelvis and core,” said Holly Silvers, PT, PhD, project coordinator for the Santa Monica Orthopedic Sports Medicine/Research Foundation.
In a study published in the December issue of the Scandinavian Journal of Medicine & Science in Sports, researchers from Copenhagen University Hospital randomized 27 of 55 soccer teams to perform an six-exercise intervention focused on pelvic strengthening, coordination, and core stability. The six exercises included: supine adduction with a soccer ball between the feet or the knees, simultaneous abdominal situps and hip flexion with a ball between the knees, “cross-country skiing” on one leg, partner-based abduction/adduction while seated, and iliopsoas stretches.
The incidence of groin injury was 31% lower in the group that performed the intervention than in the control group, but that difference was not statistically significant. More than four times as many subjects would have been required for that finding to have been significant, said lead author Per Holmich, MD, an associate research professor of anatomy and orthopedic surgery at the university, who presented the findings in Monaco.
The gods of statistical significance were a bit more generous with Silvers and colleagues, best known for the PEP anterior cruciate ligament injury prevention program, as they tested the effectiveness of a similar program designed to prevent groin injuries.
Like the PEP program, the Santa Monica groin prevention program started with a dynamic warm-up of running and shuttle drills. Players then performed strengthening exercises including supine ball rotations, bridges, side planks, and lateral adductor exercises with abduction of the contralateral leg. Cool down involved static stretching.
During a single season, the incidence of groin injuries in the 106 Major League Soccer players who performed the intervention was 28% lower than in the 209 players in a control group, a statistically significant difference. However, the incidence of groin injuries requiring surgery did not differ between groups.
Though it is difficult to tease out the benefits of specific components of a multimodal exercise program, a more focused study from the Copenhagen group may help. In a randomized controlled trial, researchers are studying the effects of a single elastic band-based adductor strengthening exercise (performed concentrically, isometrically, and concentrically) after eight weeks of training in sub-elite Danish soccer players. Preliminary results, which have not been analyzed for statistical significance, suggest improvements of 15% to 30% in isometric and eccentric muscle strength, according to graduate student Kristian Thorborg, PhD, who described the protocol in Monaco. Whether those improvements translate into reduced injury risk may be a topic for the next international sports injury prevention conference in 2014.
