E ﬀ ects of Upper-Limb, Lower-Limb, and Full-Body Compression Garments on Full Body Kinematics and Free-Throw Accuracy in Basketball Players

: Compression garments can enhance performance and promote recovery in athletes. Di ﬀ erent body coverage with compression garments may impose distinct e ﬀ ects on kinematic movement mechanics and thus basketball free-throw accuracy. The objective of this study was to examine basketball free-throw shooting accuracy, consistency and the range of motion of body joints while wearing upper-, lower- and full-body compression garments. Twenty male basketball players performed ﬁve blocks of 20 basketball free-throw shooting trials in each of the following ﬁve compression garment conditions: control-pre, top, bottom, full (top + bottom) and control-post. All conditions were randomized except pre- and post-control (the ﬁrst and last conditions). Range of motion of was acquired by multiple inertial measurement units. Free-throw accuracy and the coe ﬃ cient of variation were also analyzed. Players wearing upper-body or full-body compression garments had signiﬁcantly improved accuracy by 4.2% and 5.9%, respectively ( p < 0.05), but this di ﬀ erence was not observed with shooting consistency. Smaller range of motion of head ﬂexion and trunk lateral bending ( p < 0.05) was found in the upper- and full-body conditions compared to the control-pre condition. These ﬁndings suggest that an improvement in shooting accuracy could be achieved by constraining the range of motion through the use of upper-body and full-body compression garments.


Introduction
Basketball is one of the most popular sports; at least 450 million people play basketball worldwide, ranging from registered elite players to amateurs [1]. Basketball skills can be categorized into offensive skills, including shooting, passing and dribbling and defensive skills, including blocking and stealing [2]. While shooting is the mean to score in the game, free-throws (or foul shots) are considered as one of the easiest movements, yet they can significantly influence the outcome of a game [3,4]. Movement mechanics and coordination are key to free-throwing performance [5,6] and may be regulated by wearing compression garments [7]. the previous 6 months. Ethical approval (IRB-2017-BM-006) was granted from the institutional ethics committee. Written informed consent was obtained from all participants.

Experimental Conditions and Procedure
All free-throw shooting conditions were performed in our biomechanical laboratory. The freethrow distance and the height of the basketball rim were set according to the International Basketball Federation standards [19]. The participants performed single-handed free-throws under five different garment conditions, control-pre: no garment pre-control, Top: upper-body compression garment (Li Ning, Powershell, AULM043-I, Beijing, China), Bottom: lower-body compression garment bottom (Li Ning, Powershell, AUDL101-1, Beijing, China), full: both upper-body and lower-body compression garment and control-post: no garment post-control, as shown in Figure 1. Control-pre and control-post were the first and the last test conditions. The remaining three compression garment conditions (top, bottom and full) were randomly assigned as the second to the fourth conditions across participants. As the experimental protocol compared the first and last conditions, we were able to evaluate the fatigue effect [22]. For each free-throw condition, 20 free-throw shooting trials were performed. Testing of the next condition started immediately after the participant changed their garments.

Experimental Conditions and Procedure
All free-throw shooting conditions were performed in our biomechanical laboratory. The freethrow distance and the height of the basketball rim were set according to the International Basketball Federation standards [20]. The participants performed single-handed free-throws under five different garment conditions, control-pre: no garment pre-control, Top: upper-body compression garment (Li Ning, Powershell, AULM043-I, Beijing, China), Bottom: lower-body compression garment bottom (Li Ning, Powershell, AUDL101-1, Beijing, China), full: both upper-body and lower-body compression garment and control-post: no garment post-control, as shown in Figure 1. Control-pre and control-post were the first and the last test conditions. The remaining three compression garment conditions (top, bottom and full) were randomly assigned as the second to the fourth conditions across participants. As the experimental protocol compared the first and last conditions, we were able to evaluate the fatigue effect [23]. For each free-throw condition, 20 free-throw shooting trials were performed. Testing of the next condition started immediately after the participant changed their garments. The control conditions (control-pre and control-post) were self-selected comfortable sportswear that were not compression garments. The experimenters measured the height, waist and chest circumference of the participants to determine the appropriate garment [24]. The appropriate compression garment size was pre-determined by the manufacturer's sizing guidelines and was based on the body height and mass of each participant. Next, we assigned participants compression garments one size smaller than the pre-determined appropriate size in order to increase the interfacial pressure, as recommended by the experimental protocol detailed by Williams and colleagues [12]. A motion capturing system with multiple inertial measurement units (MyoMOTION, Noraxon, Inc., Scottsdale, AZ, USA) was used to measure full-body kinematics during the free-throw shooting trials. The inertial measurement units (IMU) were attached and strapped to each body segment according to the instrument guidelines. During each free-throw trial, the participants performed shooting from the same position behind the free-throw line. The sampling frequency of the IMU was 200 Hz. The kinematic data during the free-throw motion were post-processed using Matlab software (MathWorks, Inc., Natick, MA, USA) using a 6 Hz cutoff 4 th order Butterworth low-pass filter.

Outcome Measures
Outcome measures including performance score (accuracy) and joint ROM variables were investigated. The performance score was gauged using an ordinal six-point (0 to 5 point) scoring system. Five, four and three points denoted a clean score, that the ball hit the rim and went in, and that the ball hit the backboard and went in, respectively. Two, one and zero points denoted that the ball hit the rim and missed, hit the backboard and missed and missed complete, respectively, as illustrated in Table 1 [20,25]. The consistency of the score was also assessed by the coefficient of variation (i.e., the ratio of the standard deviation to the mean of the trials). The control conditions (control-pre and control-post) were self-selected comfortable sportswear that were not compression garments. The experimenters measured the height, waist and chest circumference of the participants to determine the appropriate garment [23]. The appropriate compression garment size was pre-determined by the manufacturer's sizing guidelines and was based on the body height and mass of each participant. Next, we assigned participants compression garments one size smaller than the pre-determined appropriate size in order to increase the interfacial pressure, as recommended by the experimental protocol detailed by Williams and colleagues [12]. A motion capturing system with multiple inertial measurement units (MyoMOTION, Noraxon, Inc., Scottsdale, AZ, USA) was used to measure full-body kinematics during the free-throw shooting trials. The inertial measurement units (IMU) were attached and strapped to each body segment according to the instrument guidelines. During each free-throw trial, the participants performed shooting from the same position behind the free-throw line. The sampling frequency of the IMU was 200 Hz. The kinematic data during the free-throw motion were post-processed using Matlab software (MathWorks, Inc., Natick, MA, USA) using a 6 Hz cutoff 4th order Butterworth low-pass filter.

Outcome Measures
Outcome measures including performance score (accuracy) and joint ROM variables were investigated. The performance score was gauged using an ordinal six-point (0 to 5 point) scoring system. Five, four and three points denoted a clean score, that the ball hit the rim and went in, and that the ball hit the backboard and went in, respectively. Two, one and zero points denoted that the ball hit the rim and missed, hit the backboard and missed and missed complete, respectively, as illustrated in Table 1 [19,24]. The consistency of the score was also assessed by the coefficient of variation (i.e., the ratio of the standard deviation to the mean of the trials). ROM of the head, trunk, elbow, shoulder, wrist, hip, knee and ankle joints in the sagittal, coronal and frontal planes were calculated. Data were averaged across trials for each participant in each condition which served as the targeted average profile for subsequent statistical analysis [25]. We did not view the within-participant effect (trial) of ROM as an independent observation or random factor to be analyzed.

Data Analysis
All statistical analysis was performed in SPSS 21 (IBM, New York, NY, USA). Prior to statistical analysis, the Shapiro-Wilk test was performed to check for the normality of the kinematic data, and it was satisfied. The Wilcoxon signed-rank test was performed to compare free-throw performance scores between the control-pre-and control-post-control conditions to ensure that there was no learning or fatigue effect (i.e., Control pre-and post-control were not significantly different). Furthermore, one-way repeated measures analysis of variance (ANOVA) was performed to examine any significant difference for joint ROM variables between the control-pre, top, bottom and full conditions, followed by the post hoc pairwise comparison of Least Significant Difference (LSD) if a significant main effect was found. We chose the LSD approach as our research hypothesis was more focused on planned comparisons. As such, we regarded the ANOVA as an additional constraint [26]. Similarly, the comparison for the performance score and the coefficient of variation was performed using a nonparametric test (Friedman test), with the post hoc pairwise Wilcoxon signed-rank test, as the performance score was gauged in an ordinal scale. Level of significance was set at p = 0.05. The indices of effect size for the ANOVA and post hoc pairwise comparison were partial η 2 and Cohen's d, respectively.

Control-Pre and Control-Post Conditions
There was no significant difference in performance score between the control-pre (Median = 2.975) and control-post (Median = 3.075) conditions (Z = −1.430, p = 0.153). Similarly, there was no significant difference in the coefficient of variation of performance score between the control-pre and control-post conditions (Z = −1.382, p = 0.167). We assumed that there was no pronounced carry-over or fatigue effect that significantly affected performance over the course of the experiment.

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, garment 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 garment condition could minimize the carry-over effect. Second, our short adaptation time for each compression garment 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.

Conclusions
Players wearing upper-body or full-body compression garment significantly improved basketball free-throw accuracy by 4.2% and 5.9%, respectively, but not on the intertrial consistency. full body kinematics data suggested that the improved performance could be attributed to the reduced ROM of head flexion and lateral bending of the trunk. Future studies investigating the relationship between shooting performance in basketball, reduced ROM and enhanced proprioception or stability are required.