A Kinematic Analysis of the Basketball Shot Performed with Different Ball Sizes
Round 1
Reviewer 1 Report
See the attached file.
Comments for author File: 
Comments.pdf
Author Response
The authors measured kinematic parameters of young players in basketball shots with two types basketballs and found the differences of the parameters. The shot with the heavier ball requires large release angle. The shooters produced large elbow and knee joints’ angular velocities with the heavier ball.
Unfortunately, I cannot recommend the article for publication because 1) valuable information is not included, and 2) I have some doubts about some measurements and information.
1) The player produces large torques at joints with a heavy ball, and the angular velocity of the corresponding joint becomes larger than that with a lighter ball. I do not think new and useful information is provided in the article. 2) Ball release height: why is the release height for ball size 6 the same as that for ball size 5 with different shoulder release angle, the same CoM maximum height, the same elbow release angle, the same knee minimum and maximum angles? Shooting efficacy: different ball release angle and velocity cause the different ball trajectories. Large release angle and small release speed shorten the shot distance in the angle larger than approximately 45◦. The optimal release angle exists for the minimum ball release speed. If the release angle differs from the optimal angle, the ball release speed should be larger. I think the shot distance with ball size 6 is short and affects the shooting efficacy. Resolution of measurement: A larger ball release angle value was observed. The difference between them in the two balls is approximately one degree. Is it possible for the measurement system to detect one-degree difference? It is difficult to accept the assumption that the same release height and different release angles and velocities produce the same shooting efficacy.
Response: We appreciate the reviewer feedback on our work. We assume the limitations in the measuring system, and we believe that a more sophisticated analysis would be far more informative. Unfortunately, we did not have different instruments for the shooting assessment. We also understand the questions regarding the ball release height. Please note that all shots (missed or scored) were considered in our analysis, in a total of 540 shots. We performed a pilot study with 10 athletes and randomly selected 30 trials from 300 recorded to assess the intra-observer reliability. In that study, we achieve good to excellent reliability. In this study, the video analysis was performed by the same investigator, and we are confident in the measurement system. In terms of efficacy percentage, there was a variation of 5% which is not significant. Even though, we believe that this could also lead us to the conclusion that short-term manipulation of the ball size is not enough to significantly affect the shooting action. This conclusion was also reported in two previous studies developed in the topic. The authors described a consistent movement performance (including the ball release variables analysis) although the used different ball sizes.
Satern, M. N. (1986). The effect of ball size and basket height on the mechanics of the basketball free throw as performed by seventh grade boys (Doctoral dissertation, The University of North Carolina at Greensboro).
Okazaki, V. H. A., & Rodacki, A. L. F. (2005). Changes in basketball shooting coordination in children performing with different balls. Fédération Internationale D’éducation Physique, 75(2), 368-371.
Reviewer 2 Report
Please check and address my comments and suggestions point by point.
Comments for author File: Comments.pdf
Author Response
- In my opinion, the article is written following the guidelines and the topic is interesting from a standpoint of development of basketball game for young selections. I want to point out some suggestions that in my opinion should be further explained or added.
Response 1: The authors appreciate the reviewer's positive feedback.
- Introduction. Since the title relates to determination of kinematic differences between basketball shot with different ball sizes, it is not clear why the authors conducted correlation analysis. I do not understand how performed analysis along with selected variables influences the main aim of the research. Maybe this part of analysis should be integrated as a secondary aim of the paper, so it is clearer for the readers. Please add some additional explanation regarding mentioned above.
Repsonse 2: The authors would like to appreciate this useful suggestion. This information was added in the Introduction section.L. 72-78: “On the other hand, the literature has mentioned that players who are less able to produce force, such as female players and children, are required to use more movement velocity while shooting [1,2]. A greater contribution from the shoulder joint to generate impulse applied to the ball was found in female players, particularly due to their lower upper-body strength compared to their male counterparts [1]. Strength appears as an important variable for the shooting performance, although little data has been found on this topic.”
- 86-87: “The secondary purpose of this study was to assess the relationship between strength tests and the selected kinematic variables.”
- Materials and Methods. Could you please add some explanation regarding the chosen fitness tests? How do this tests affect the overall aim of your research?
Response 3: The fitness tests selected have been widely used to assess strength. We have now included in the Introduction section information on the importance of strength for basketball shooting performance, which we think is crucial considering our sample. Therefore, the authors believed that exploring the relationship between strength and kinematic variables is valuable and innovative data for shooting research.
- For example, you mentioned that you used 2 lower limb explosive tests, but you only described CMJ (also, in further analysis you only analysed CMJ, without mentioning the other test). Also, did you use the best or average result for analysis?
Response 4: We would like to thank the reviewer for this detailed reading. We have now updated the text in the Fitness Test section. In all fitness tests, the best score was used for analysis. This information was also added to the testing protocols.
- Please, ass the details of the position and protocol for 2kg medicine ball throw since it is not well explained.
Response 5: The position and protocol for 2kg medicine ball throw is described in more detail as follow: “The 2 kg medicine ball throw is based on three trials with 30 seconds of rest between tests. The throws were made above the head in a standing position and with both feet parallel. If participants lost their balance or varied their position while throwing, the test was repeated. Participants were incentivized to throw the medicine ball as far as they can. The best score was retained for analysis.” (L.145-149)
- It is unclear how the authors selected number of analysed shots. It is mentioned that each of the 27 players performed 10 shots. How did you decide what is sufficient number of shots for conducted analysis? Have you performed power analysis? Please explain.
Response 6: Each participant performed 10 BS with each ball, making a total of 20 attempts for each player. Therefore, the total of BS performed was 540 and all were considered in the statistical analysis. Unfortunately, we did not perform a power analysis. However, we believe that the number of shooting attempts was large. This information has been added in the Shooting section. L. 178: “After data collection, a total of 540 video recordings (20 from each participant) were exported and analyzed using Tracker software (Open-Source Physics – Video Analysis and Modelling Tool, 5.1.5) to assess the kinematic variables.”
- Is the chosen statistical analysis (a large number of t-tests) suitable for this research design? Based on the number of observed variables, maybe more suitable is MANOVA.
Response 7: The authors would like to thank the reviewer for this useful suggestion. We have run the MANOVA analysis and updated the manuscript with the new results.
- Results. Line 232-241: Please, add more explanation for tables 3 and 4. The correlation between variables is not well described.
Response 8: We performed the Pearson correlation among all tested variables (kinematic, anthropometry and fitness tests). However, to facilitate the readers' point of view, we opted to report only the significant results of that analysis in Tables 3 and 4. We have now explained this in the text. L. 256-259: “The Pearson-product correlation coefficient was used to assess the relationships between all kinematic parameters analyzed, anthropometry and fitness variable. In Tables 3 and 4 are presented only the significant results of the Pearson-product correlation coefficient according to the ball size used.”
- Discussion. Please add some more details about connection of performed fitness tests and gained kinematic results. What is the main limitation of this research? Please explain. What is the scientific contribution of your research? Try to explain.
Response 9: In the Discussion section we have now added more details regarding the Pearson correlations. L 316-334: “Meanwhile, strength has been described as a crucial capacity to generate the impulse needed to throw the ball. Players who are less able to generate force, such as females and children, have a more challenging time while shooting [2]. Therefore, it is essential to understand the relationship between the shooting motor action and the shooter’s anthropometric and fitness characteristics. To the best of our knowledge, this is the first study considering this type of analysis. According to our results, the ball release height showed the highest number of relationships independently of the ball size. Past literature suggests that a strong and positive correlation was found between ball release height and stature [31]. Body mass also emerged with a strong and positive relationship with ball release height (r = > 0.71 < 0.77), which should be related to strength. Indeed, both the handgrip and the 2 kg ball throw presented strong correlations with ball release height (positive), ball release angle (negative), and joints’ peak angular velocities. Strength should contribute to generating ball velocity, and if velocity increases, the angle at ball release should decrease. Thus, upper-body strength appears as an important predictor of ball trajectory. In contrast, the CMJ was significantly and negatively related to the ball release height. It would be expected a linear and positive correlation between both variables; however, this result must be interpreted together with the other variables in the analysis. In fact, the literature has described the positive relationship between body mass and strength during the adolescent years and the detrimental effect of body mass in jumping tasks [3].”
In our opinion, the main limitation of this research is the use of a 2D analysis for data collection instead of a 3D analysis, which would be more sophisticated and far more informative. Unfortunately, we did not have the instruments needed to perform a 3D analysis at the time of data collection and we assume this as the main limitation.
We believe that this research brings important scientific and practical implications, particularly for the ones involved in youth basketball age categories. The ball size is an important element of the training and competition process which is expected to influence the performance of specific skills, and that is modified according to age and sex. Through this research, we concluded that ball size manipulation could be used as a strategy during the early stages of the basketball training process and among more inexperienced players to enhance optimal shooting patterns. In the case of female youth players, the increase in basket height and ball size in the transition to the U14 age category represents a shooting constraint, particularly due to their lack of strength. Consequently, the shooting action does not follow the guidelines of the reference technical model, which results in long-term adaptations and low efficacy levels.
Reviewer 3 Report
I have thoroughly reviewed manuscript of Franca et al. titled: ”A kinematic analysis of the basketball shot performed with different ball sizes”.
Firstly, I want to congratulate the group of authors for this interesting article focused on kinematics of the basketball shot in youth selection. I find the article well written according to guidelines and flow of the manuscript which confirms that the manuscript was written by an experienced group of authors. I need to point out several things in this manuscript which need to be further explained, changed or added.
· Introduction
The rationale for the study is well explained for readers. Since there is correlation analysis used in the results, there should be further explanation and rationale of why this is important for understanding basketball shot kinematics. The main focus of this research are kinematic differences between two ball sizes and it is unclear why the authors performed strength tests and correlation analysis. Further explanations are needed in the introduction and the secondary aim of this research should be added.
· Materials and Methods
Line 87: regarding the ethical approval, the sentence is not finished and is lacking the committee’s name.
Line 111: It is stated that ”In both tests, participants were…”, and there is only one test (CMJ) explained in the text.
Line 134-136: The throwing position needs to be further explained as it can be from different positions.
Line 138-160: What is the total number of BS performed? Were all performed shots taken in consideration for statistical analysis?
Line 202-211: Why did the authors use the t-test in statistical analysis and analyse each parameter separately? The basketball shot is a unique element and all variables should be included into one analysis with implementation of the MANOVA. Please explain.
Information about whether the average or best values in fitness tests were considered in statistical analysis need to be added in the text.
· Results
Line 232 – 241: There is a lack of explanation of the presented variables.
· Discussion
Please refer to the CMJ results and negative correlation to ball release height.
Author Response
- Firstly, I want to congratulate the group of authors for this interesting article focused on kinematics of the basketball shot in youth selection. I find the article well written according to guidelines and flow of the manuscript which confirms that the manuscript was written by an experienced group of authors. I need to point out several things in this manuscript which need to be further explained, changed or added.
Response 1: The authors would like to thank the reviewer for feedback on the importance of this article.
- Introduction. The rationale for the study is well explained for readers. Since there is correlation analysis used in the results, there should be further explanation and rationale of why this is important for understanding basketball shot kinematics. The main focus of this research are kinematic differences between two ball sizes and it is unclear why the authors performed strength tests and correlation analysis. Further explanations are needed in the introduction and the secondary aim of this research should be added.
Response 2: The authors appreciate this useful suggestion. This information was added in the Introduction section. L. 72-78: “On the other hand, the literature has mentioned that players who are less able to produce force, such as female players and children, are required to use more movement velocity while shooting [1,2]. A greater contribution from the shoulder joint to generate impulse applied to the ball was found in female players, particularly due to their lower upper-body strength compared to their male counterparts [1]. Strength appears as an important variable for the shooting performance, although little data has been found on this topic.”
- 86-87: “The secondary purpose of this study was to assess the relationship between strength tests and the selected kinematic variables.”
- Materials and Methods
3.1. Line 87: regarding the ethical approval, the sentence is not finished and is lacking the committee’s name.
Response 3.1.: The information regarding the ethical approval is now completed. L. 96-97: “The current study received ethical approval from the committee of the University of Coimbra (CE/FCDEF-UC/00482019).”
3.2. Line 111: It is stated that ”In both tests, participants were…”, and there is only one test (CMJ) explained in the text.
Response 3.2.: Thank you for your careful reading. The CMJ protocol is now updated. L. 120-125: “Participants rest 45 seconds between each trial and five minutes between each test. Participants were directed to perform the CMJ "as they usually would" with a quick countermovement to a comfortable depth emphasized before exploding upwards to gain maximum height. Hands remained on the hips for the entire movement to eliminate any influence of arm swing. During testing, participants were encouraged to jump to maximum height.”
3.3. Line 134-136: The throwing position needs to be further explained as it can be from different positions.
Response 3.3.: The throwing position is now described in detail in the Fitness tests section. L. 145-149: “The 2 kg medicine ball throw is based on three trials with 30 seconds of rest between tests. The throws were made above the head in a standing position and with parallel feet. The test was repeated if participants lost their balance or varied their position while throwing. Participants were incentivized to throw the medicine ball as far as they could. The best score was retained for analysis.”
3.4. Line 138-160: What is the total number of BS performed? Were all performed shots taken in consideration for statistical analysis?
Response 3.4.: Each participant performed 10 BS with each ball, making a total of 20 attempts from each player. Therefore, the total of BS performed was 540 and all were considered in the statistical analysis. This information has been added in the Shooting section. L. 178: “After data collection, a total of 540 video recordings (20 from each participant).”
3.5. Line 202-211: Why did the authors use the t-test in statistical analysis and analyse each parameter separately? The basketball shot is a unique element and all variables should be included into one analysis with implementation of the MANOVA. Please explain.
Response 3.5.: The authors would like to thank the reviewer for this useful suggestion. We have run the MANOVA analysis and updated the manuscript with the new results.
3.6. Information about whether the average or best values in fitness tests were considered in statistical analysis need to be added in the text.
Response 3.6.: The best score on the fitness tests were used for analysis. This information was added to the text after each protocol description.
- Results. Line 232 – 241: There is a lack of explanation of the presented variables.
Response 4: As previously suggested, the results section has been updated according to the MANOVA results. The presented variables are now explained in more detail.
- Discussion. Please refer to the CMJ results and negative correlation to ball release height.
Response 5: Although it would be expected a positive correlation between CMJ height and the ball release height, this result must be interpreted together with the other variables. The strong and positive relationship observed between ball release height and body mass might justify the negative correlation between CMJ and ball release height. Indeed, literature has consistently described the negative influence of increased body mass (particularly by the possibility of also representing an increased body fat percentage) in jumping tasks. L. 330-334: “In contrast, the CMJ was significantly and negatively related with the ball release height. It would be expected a linear and positive correlation between both variables; however, this result must be interpreted together with the other variables in the analysis. In fact, the literature has described the positive relationship between body mass and strength during the adolescent years, and also the detrimental effect of body mass in jumping tasks [3].”
Reviewer 4 Report
Interesting study with a bit unexpected results.
The 2 kg ball throw is significantly and positively related to the ball release height which can be expected. But we can find negative correlation between ball no 6 and release angle and medicine ball throw which is surprising. Please try to find some additional explanation for such a results.
Author Response
Interesting study with a bit unexpected results. The 2 kg ball throw is significantly and positively related to the ball release height which can be expected. But we can find negative correlation between ball no 6 and release angle and medicine ball throw which is surprising. Please try to find some additional explanation for such a results.
Response 1: We appreciate the overall positive feedback from the reviewer. Our analysis also showed a positive relationship between the 2 kg ball throw and the ball release velocity (r = 32, p = 0.11). However, in Table 4 we only presented the significant results from the Pearson correlation. Therefore, since the literature mentions that the angle and velocity of ball release are characterized by an inverse behaviour (which is also shown in our results), we assume that the negative correlation between the 2 kg ball throw and the ball release angle is related with the positive correlation between the 2 kg ball throw and the ball release velocity. This information has been added to the Discussion as follows: ”Strength should contribute to generating ball velocity, and if velocity increases, the angle at ball release should decrease, which should justify the negative correlation between the 2 kg ball throw and the ball release angle.” (L.327-330).
Round 2
Reviewer 1 Report
The authors measured kinematic parameters of young players in basketball shots with two types basketballs and found the differences of the parameters. Large shoulder angular displacement is found in the shooting motion with size 6 (heavier) ball. The shoulder angles for the two ball are different at release. For 6, large shoulder flexion is observed and the release height is a little lower. No significant differences are in the elbow and knee motions. I recognize this measurement is a new attempt in the field of the sports measurement and accept the article. I confirmed the result does not contradict the measurement.
