RESUMO
Background: Currently, most pitching instructors suggest a shorter arm path-the total distance the arm travels during pitching. Theoretically, this combination allows for better body segment sequencing, a more efficient energy transfer through the kinetic chain, and increased ball velocity, while limiting elbow varus torque. Hypothesis: Shorter arm paths would be associated with increased ball velocity and decreased elbow varus torque. Study Design: Descriptive laboratory study. Methods: A total of 182 professional pitchers threw 8 to 12 fastball pitches while evaluated by 3-dimensional motion capture (480 Hz). The arm path was calculated as the total distance the hand marker traveled during the pitch. The pitch was divided into early, late, and total arm paths. A linear regression model assessed the interpitcher relationship between arm path, elbow varus torque, and ball velocity. A linear mixed-effects model with random intercepts assessed intrapitcher relationships. Results: Interpitcher comparison showed that total arm path weakly correlated with greater elbow varus torque (P = .025). Strong correlations were found between ball velocity and early (R2 = 0.788; P < .001), late (R2 = 0.787; P = .024), and total arm paths (R2 = 0.792; P < .001). Strong positive intrapitcher correlations were found between elbow varus torque and early (R2 = 0.962; P < .001) and total arm path (R2 = 0.964; P < .001). For individual pitchers, there was a large variation in the early (30.1 ± 15.7 cm) and late (21.4 ± 12.1 cm) arm path. For every 30-cm (11.8-inch) increase in early arm path (the mean range for an individual pitcher), there was a 1.29-N (ß = 0.0429) increase in elbow varus torque and a 0.354 m/s (0.79 mph) (ß = 0.0118) increase in ball velocity. Conclusion: A shorter arm path correlated with decreased elbow varus torque and decreased ball velocity in intrapitcher comparisons. Determining the individual mechanics that decrease elbow varus torque may help coaches and trainers correct these patterns. Clinical Significance: A shorter arm path during the pitch can decrease elbow varus torque, which limits the load on the medial elbow but also has a detrimental effect on ball velocity. An improved understanding of the impact of shortening arm paths on stresses on the throwing arm may help minimize injury risk.
RESUMO
This study investigated the accuracy of the Insole3 wireless shoe device in estimating several clinically useful spatiotemporal parameters (STPs). Eleven subjects walked at slow (0.8-1.0 m/s) and moderate-paced (1.2-1.4 m/s) speeds. Data were simultaneously recorded using the Insole3 and an industry-standard, three-dimensional motion capture (MOCAP) system. An error analysis compared the resulting STP data from the two systems. The mean bias error (MBE) was generally lower for temporal variables, and somewhat higher, but acceptable, for spatial variables. The MBE for temporally-related cadence and cycle time were the lowest (less than ±0.45%), with 100% (110/110) of slow-paced walking trial values and 99.1% (109/110) of moderate-paced walking trial values within 5% of the MOCAP estimates. The MBE was highest for speed (3.23-4.91%) and stride length (3.68-4.63%), with between 52.7 and 69.1% of trial values falling within the 5% error range. Stance time and swing time ranged between -0.98 and 4.38% error for both walking conditions. The results of this study suggest that the Insole3 is a potential alternative to MOCAP for estimating several STPs, namely cadence, stance time, and cycle time, particularly for use outside of the laboratory setting.