Purpose: Recent research indicates that a concussion increases the risk of musculoskeletal injury. Neuromuscular changes after concussion might contribute to the increased risk of injury. Many studies have examined gait postconcussion, but few studies have examined more demanding tasks. This study compared changes in stiffness across the lower extremity, a measure of neuromuscular function, during a jump-landing task in athletes with a concussion (CONC) to uninjured athletes (UNINJ).
Methods: Division I football players (13 CONC and 26 UNINJ) were tested pre- and postseason. A motion capture system recorded subjects jumping on one limb from a 25.4-cm step onto a force plate. Hip, knee, and ankle joint stiffness were calculated from initial contact to peak joint flexion using the regression line slopes of the joint moment versus the joint angle plots. Leg stiffness was (peak vertical ground reaction force [PVGRF]/lower extremity vertical displacement) from initial contact to peak vertical ground reaction force. All stiffness values were normalized to body weight. Values from both limbs were averaged. General linear models compared group (CONC, UNINJ) differences in the changes of pre- and postseason stiffness values.
Results: Average time from concussion to postseason testing was 49.9 d. The CONC group showed an increase in hip stiffness (P = 0.03), a decrease in knee (P = 0.03) and leg stiffness (P = 0.03), but no change in ankle stiffness (P = 0.65) from pre- to postseason.
Conclusion: Lower extremity stiffness is altered after concussion, which could contribute to an increased risk of lower extremity injury. These data provide further evidence of altered neuromuscular function after concussion.
1Department of Physical Therapy, College of Public Health and Health Professions, University of Florida, Gainesville, FL; 2Department of Orthopaedics and Rehabilitation, College of Medicine, University of Florida, Gainesville, FL; 3Department of Community Health and Family Medicine, College of Medicine, University of Florida, Gainesville, FL; 4Department of Athletics, University of Texas, Austin, TX; 5Department of Large Animal and Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville FL; 6Department of Anesthesiology, College of Medicine, University of Florida, Gainesville, FL; and 7TRIA Orthopaedic Center, Bloomington, MN
Address for correspondence: Dominique F. DuBose, M.S., A.T.C., Department of Physical Therapy, University of Florida, Box 100154, UFHSC, Gainesville, FL 32610-0154; E-mail: firstname.lastname@example.org.
Submitted for publication December 2015.
Accepted for publication July 2016.