Lumbopelvic Stability During a Single Leg Step Down Predicts Elbow Varus Torque During Baseball Pitching

During a baseball pitch, energy is transferred from the lower extremities through the lumbopelvic junction to produce ball velocity. Reduced lumbopelvic stability has been associated with elbow injury in pitchers, and commonly ulnar collateral ligament (UCL) tears. The primary biomechanical mechanism of UCL tears is high elbow varus torque. Understanding how decreased lumbopelvic stability influences the development of elbow varus torque could identify risk factors of UCL elbow injury. PURPOSE: Characterize the predictive ability of lumbopelvic stability on elbow varus torque during a baseball pitch. METHODS: NCAA Division 1 baseball players (N=44; 19.6+1.3yrs) participated. Pitchers threw ten fastballs from a mound to a catcher over regulation distance. Elbow varus torque was recorded using an inertial measurement unit and ball velocity was recorded with a radar gun. Pitchers also completed a single leg step down (SLSD) task. Triplanar kinematics were recorded for both legs, pelvis and trunk using inertial measurement units. Statistical analysis consisted of a cluster analysis, principal component analysis (PCA), and a multivariate logistic regression model to determine the relationship between lumbopelvic stability and elbow varus torque. RESULTS: Cluster analysis revealed 2 subgroups of pitchers: Low Torque-High Velocity and High Torque-Low Velocity. PCA analysis indicated 4 patterns of SLSD motion variability (principal components): 1-sagittal plane, 2-transverse plane, 3-frontal plane trail limb, and 4-frontal plane lead limb. Increased transverse plane motion of the trunk and pelvis predicted higher odds of belonging to the High Torque-Low Velocity cluster; trunk [Odds Ratio=2.9 (95%CI:1.1,8.0), p=0.036] and pelvis [Odds Ratio=2.6 (95%CI:1.1,6.0), p=0.031]. CONCLUSIONS: Lumbopelvic motion assessed during the SLSD in pitchers can identify deficits that predict high elbow varus torque and low ball velocity during the baseball pitch. Specifically, higher pelvis and trunk transverse plane motion was associated with pitchers in the High Torque-Low Velocity cluster. The SLSD provides an easily accessible method for coaches and clinicians to identify a potential risk factor related to increased elbow varus torque and UCL injury in pitchers

Force-plate derived predictors of lateral jump performance in NCAA Division-I men's basketball players.

A lateral jump assessment may provide unique benefits in sports such as basketball that require multidirectional performance optimization. This study aimed to examine selected force-plate derived metrics as predictors of lateral jump task distance in men's basketball players. Twenty-two NCAA Division-I men's basketball players (19.4 ± 1.3 years, 95.0 ± 12.5 kg, 196.5 ± 8.1 cm) each performed six single leg lateral jumps while standing on a force plate (1200 Hz, Kistler Instrument Corp). The lateral jump task involved the subject beginning by standing on the force plate and jumping sideways off one foot and then landing on the floor with the opposite foot. Three-dimensional ground reaction force curves were used to identify the eccentric and concentric phases of the jump and variables were computed each from the lateral (y), vertical (z), and resultant (r) force traces. Peak ground reaction force (pGRF), ground reaction force angle (θr), eccentric braking rate of force development (ECC-RFD), average concentric force (CON-AVG), total jump duration, eccentric phase duration, and eccentric to total time ratio were evaluated for predictive ability. Three regression models were able to significantly (p<0.05) predict jump distance: (1) pGRFy, pGRFz, and θr (p<0.001, R2 = 0.273), (2) Relative pGRFy, Relative pGRFz, and θr ((p<0.001, R2 = 0.214), and (3) Relative CON-AVGy and Relative pGRFr (p<0.001, R2 = 0.552). While several force plate-derived metrics were identified as significant predictors, a model with Relative CON-AVGy and Relative pGRFr explained a greater variability in performance (R2 = 0.55) compared to the other variables which were low, yet also significant. These results suggest that lateral ground reaction forces can be used to evaluate lateral jump performance with the use of three-dimensional force plates. The identified predictors can be used as a starting point for performance monitoring, as basketball training interventions can be directed at specific improvements in the identified metrics