No abstract

Marker placement deviation has been shown to be the largest source of error in gait kinematic data, limiting the ability of clinicians and researchers to conduct between-day or between-center investigations. Prior marker-placement standardization methods are either impractical for a clinical setting or rely on expert marker placement. However, a recently developed, real-time feedback tool has been developed and shown to improve marker placement and downstream kinematic calculations. The purpose of this study was to determine whether this real-time marker-placement tool could improve the consistency of gait kinematic data collected by a group of novice examiners. Twelve novice examiners identified anatomical landmarks and placed retroreflective markers on a single subject. For each examiner, a running trial was analyzed separately using two static trials: (1) PRE and (2) POST implementation of the feedback tool. The protocol was repeated a second time, one week later. Between-examiner consistency was represented by the 95% confidence interval (CI) of the mean joint angles for the entire stride, and compared between the PRE and POST conditions. The POST feedback trials showed an average 27.45% reduction of the 95%CI range for eight out of nine joint angles on day one, and an average 24.73% for five out of nine joint angles on day two, compared to POST. The results indicate a real-time feedback tool improves the consistency in marker placement for novice users.

Lacrosse requires the coordinated performance of many complex skills. One of these skills is shooting on the opponents' net using one of three techniques: overhand, sidearm or underhand. The purpose of this study was to (i) determine which technique generated the highest ball velocity and greatest shot accuracy and (ii) identify kinematic and kinetic variables that contribute to a high velocity and high accuracy shot. Twelve elite male lacrosse players participated in this study. Kinematic data were sampled at 250 Hz, while two-dimensional force plates collected ground reaction force data (1000 Hz). Statistical analysis showed significantly greater ball velocity for the sidearm technique than overhand (P < 0.001) and underhand (P < 0.001) techniques. No statistical difference was found for shot accuracy (P > 0.05). Kinematic and kinetic variables were not significantly correlated to shot accuracy or velocity across all shot types; however, when analysed independently, the lead foot horizontal impulse showed a negative correlation with underhand ball velocity (P = 0.042). This study identifies the technique with the highest ball velocity, defines kinematic and kinetic predictors related to ball velocity and provides information to coaches and athletes concerned with improving lacrosse shot performance.