Preseason weight-bearing symmetries differ in athletes sustaining lower extremity injury during the competitive season [abstract] Abstract uri icon
  • PURPOSE/HYPOTHESIS: Symmetrical weight-bearing between limbs during athletic tasks is often a focus of preseason training programs. The specific relationship between weight-bearing symmetries during athletic tasks and injury risk has not been demonstrated. Therefore the purpose of this study was to (1) compare preseason lower extremity weight-bearing symmetry during different athletic tasks between athletes who did or did not sustain a lower extremity injury during the subsequent season and (2) determine a threshold for injury risk. NUMBER OF SUBJECTS: One hundred thirty-seven Division I collegiate athletes (98 male football, 17 female volleyball, 22 female basketball). MATERIALS/METHODS: An overhead squat (OHS), single-leg forward land (FL) and drop vertical jump (DVJ) were performed during a preseason screening. The OHS was performed with each foot on a force plate, and the subjects descended until thighs were parallel to the floor. The FL was performed from a 25-cm step, and subjects landed on the test leg on a force plate. The DVJ was performed from a 30-cm step, and subjects landed with each foot on a force plate followed by an immediate maximum vertical jump. Vertical ground reaction forces were measured at the lowest point of the sacrum for the OH, in the first 500 milliseconds after landing in the FL and at peak knee flexion in the DVJ. A symmetry index was calculated using the formula: absolute value [(right side – left side)/ body weight [(N)] × 100%]. Athletic training records from the subsequent season identified athletes with any lower extremity injury resulting in loss of training, practice or game time. Independent-samples t tests compared weight-bearing symmetry in the tasks between injured versus noninjured groups. When significant differences were found, positive and negative likelihood ratios were calculated with a threshold determined from a receiver operating characteristic (ROC) curve. The threshold was chosen based on minimizing the risk of false negatives. RESULTS: Sixty-four athletes sustained lower extremity injuries. Significant group differences were found for DVJ (13.0% ± 10.2% BW versus 17.4% ± 12.4% BW, P = .026), but not OHS (4.78% ± 3.9% BW versus 4.88% ± 3.9% BW, P = .882) or FL (24.1% ± 19.1% BW versus 30.0% ± 21.6% BW, P = .090). Based on the ROC curve, a cutoff score of 23.1% BW produced a positive likelihood ratio of 1.47 and negative likelihood ratio of .88 (P = .03). CONCLUSIONS: Athletes with a time-loss lower extremity injury during the season showed greater weight-bearing asymmetry in the DVJ at preseason testing. A weight-bearing asymmetry of 23.1% BW or greater during the DVJ slightly increased the likelihood of sustaining a lower extremity injury. Weight-bearing symmetry in OHS and FL did not significantly differ between the injured and noninjured groups. CLINICAL RELEVANCE: Asymmetries were present in all athletic tasks, however only the DVJ was associated with injury risk. Measuring weight-bearing symmetry during the DVJ may complement other screening methods for lower extremity injury risk.

  • publication date
  • 2017
  • Research
  • Injuries
  • Risk Factors
  • Sports
  • Additional Document Info
  • 47
  • issue
  • 1