Biomechanical Effects Of Assistive Equipment On Wheelchair Softball Batting

Wheelchair softball is an adaptation of slow pitch softball. The rules allow athletes to use unique assistive equipment and strategies to improve batting performance, including wheelchair “blocks” and “cages,” which allow for one-handed and two-handed swings to be performed, respectively. However, there is no consensus on strategy implementation and equipment usage due to the lack of available objective data on the performance components of the swing. PURPOSE: To investigate the effects of assistive equipment (i.e., block, cage) on batting kinematics and kinetics in wheelchair softball swing. METHODS: Wheelchair batting trials of 12 adaptive athletes (age = 33.8 ± 11.0 years; 9 males) were captured using an optical motion capture system, and five force plates. Participants performed six maximal-effort swings off of a tee in three assistive batting conditions: block, cage, and no equipment. A total of 52 retroreflective markers were applied to the body of the participant, bat, and wheelchair. The group means were compared using MANOVA, and alpha for each MANOVA was corrected to 0.017 (Bonferroni). RESULTS: Participants generally exhibited faster bat speeds, larger magnitudes of pivoting torque, and larger magnitudes of pelvic (i.e., wheelchair) and shoulder angular displacements and velocities in the equipment conditions than in the no-equipment condition. The cage and block conditions generally exhibited similar batting results, however, batting trials with the block produced larger magnitudes of upper lever and lower lever angular displacements as compared to batting trials with the cage. CONCLUSION: Assistive batting equipment (i.e., block, cage) may lead to optimal batting performance for athletes in wheelchair softball. These results also serve as the foundation for understanding the complexity of the wheelchair batting swing. Table 1: Wheelchair Batting Results. - Performance Variables Assistive Batting Equipment No Equipment Block Cage Significance Performance Variables Peak Bat Velocity (m/s) 21.3 ± 5.5 21.4 ± 4.0 23.2 ± 5.3 NE < C Swing Time (ms) 391 ± 92 397 ± 46 332 ± 73 NE > C Peak GRF Combined Z (BW) 1.3 ± 0.4 1.3 ± 0.2 1.2 ± 0.3 NE > C Peak Pivoting Moment Z (10-2 BW·cm) 1.9 ± 1.1 4.7 ± 1.7 4.1 ± 1.5 NE < B|C Range of Motion (deg) Upper Lever 95 ± 15 114 ± 13 103 ± 18 NE < C < B Lower Lever 159 ± 31 183 ± 33 163 ± 32 NE|C < B Pelvis Line -28 ± 13 5 ± 3 3 ± 3 NE > B|C Shoulder Line 54 ± 15 78 ± 14 70 ± 16 NE < B|C Max. Angular Velocity (deg/s) Upper Lever 628.5 ± 181.8 634.0 ± 77.7 701.7 ± 159.3 - Lower Lever 1052.3 ± 200.5 1059.8 ± 178.8 1117.6 ± 167.5 - Pelvis Line AV -143.5 ± 52.9 18.3 ± 13.5 22.4 ± 22.8 NE < B|C Shoulder Line AV 290.7 ± 104.0 400.9 ± 74.5 387.3 ± 110.4 NE < B|C Abbreviations: GRF = Ground Reaction Force, AV = Angular Velocity.