**4. Discussion**

This study examined the effect of upper and lower-body compression garments on the body kinematics and shooting accuracy of basketball free-throws. Our study found that upper-body (top) or full-body (top + bottom) compression garments significantly improved the performance of basketball free-throws; however, there was no significant improvement in the consistency of performance. Overall, mechanically, compression garments had a significant influence on the ROM of the head flexion, trunk lateral bending, left (non-dominant side) shoulder flexion, right (dominant side) shoulder rotation and left knee flexion as indicated by the ANOVA findings. Post hoc comparisons showed that wearing either upper- or full-body garments constrained the ROM of head flexion and trunk lateral bending which could be associated with improved trunk stability and thus, improved performance [27]. The relationship between the condition of the head movement and stability and free-throw accuracy was advocated previously, but not well understood [28]. On the other hand, garmen<sup>t</sup> coverage of the lower body (bottom or full-body gear) significantly reduced the ROM of the left (non-dominant) side knee joint in the sagittal plane, but not the right (dominant) side, because experienced players tended to adjust the knee joint of the dominant side to greater extent for better performance [29]. Theoretically, compression of the knee joint enhanced proprioception and thus performance [30,31] notwithstanding that our study did not demonstrate an improved shooting score for lower-body (bottom) garments. In addition, the reduced head flexion and trunk lateral bending ROM could implicate successful shooting performance.

Elbow and wrist movements are determinants of free-throw performance and player skill levels [20]. Skilled players coordinate the shooting arm by constantly compromising between elbow and wrist movements to adapt to subtle changes in release parameters of the ball (e.g., release height, angle of ball projection, velocity at ball release) [20]. In addition, more highly skilled players tend to maximize the ROM of the wrist joint [20]. top compression garments help to constrain the ROM of the elbow, and thus players can focus on optimizing distal joint (wrist) motion only [20]. In our study, although there were no significant main effects on the ROM of the elbow and wrist joints, pairwise comparisons showed that upper-body (top) garments significantly reduced the ROM of the right (dominant) side elbow, but increased that of the wrist radial/ulnar deviation and palmar rotation compared to that of the control-pre condition. This was likely due to the fact that the uncovered wrist joint compensated the reduced motion of the elbow [20]. In fact, some statisticians argued that conducting and interpreting post hoc analyses could still be valid even though the main effect was not significant [32,33].

The enhanced proprioception by compression garments may also facilitate the organization of compensatory behavior between joints for better performance. This was supported by existing studies that the proprioception (joint position sense) of the elbow and wrist joints was correlated with the success rate of the free-throw tasks [34]. More highly skilled players managed to optimize their performance based on the perceptual consequence of their actions [35].

A previous study suggested that the shoulder joint plays an important role in the action of basketball free-throws. Kaya et al. [36] found that free-throw performance was significantly correlated with the peak torque of the shoulder joint muscles and the shoulder joint position sense at 160◦ in the dominant side. While we anticipated that compression garments would amplify the proprioception [30], enhance stability and reduce the ROM of the shooting limb (right side), our study found that the ROM of the upper-body was significantly smaller when wearing top compression garments than when wearing bottom garments. Although there were no significant differences compared to that of the control-pre condition, we believe that the increased trend of the joint ROM may indicate that wearing lower-body (bottom) garments alone had a negative effect on the shoulder joint. From the kinetic chain perspective, intervention at the lower limb level may alter energy generation which can be transferred to the upper limbs and thus considerably influences upper limb movement tasks (e.g., racket and ball speed in racket sports) [19,37]. The influence of lower limb garments on the upper limbs may also be the reason that the full-body garments did not have an effect on the elbow and wrist joints, despite upper-body garments having an effect.

There were some limitations in this study. First, although we demonstrated no carry-over effect as revealed by the fact that there was no significant difference between the performance score of the control-pre and control-post conditions, there was an improvement trend on both the performance score and consistency. We believed that the randomized order assigned on the garmen<sup>t</sup> condition could minimize the carry-over effect. Second, our short adaptation time for each compression garmen<sup>t</sup> condition may not be adequate enough, despite that there is no consensus on the duration of adaptation in the past studies. Future studies may consider tests with longer adaptation in different days or weeks or considering the variation of kinematic variables [38]. Third, we presented only joint ROM in this study. More comprehensive analysis with discrete variables (peak angle, angular velocity), joint power, muscle force, proprioception as well as stability should be considered to evaluate their influence and underlying mechanism on the free-throw shooting performance. Asymmetry sport activity (e.g., single-handed shooting) may produce unique sequential coordination of the upper and lower limb with coherent patterns of muscle activation [39]. Forth, our study confined to non-professional basketball players. Playing level and sex effects may contribute to variations in movement strategy, skeletal alignment and muscle strength and could also be investigated. Lastly, the compression garments may impose different levels of pressure on the participants depending on their body built. Future study shall consider measuring the compression level in each condition.
