Effect of Lower Extremity Muscle Strength on Aerobic Capacity in Adults with Cerebral Palsy
Round 1
Reviewer 1 Report
This research paper studies the relationship between the muscle strength of the lower limbs and aerobic capacity of people with cerebral palsy, and is judged to have high academic value. The research method is appropriate and the results of the stepwise method used in the analysis are very interesting. There is no need to change the content of the treatise. However, since there is a problem with English expression, I think it is necessary to proofread by a native speaker.
Author Response
Thank you for insight on the important part of my research.
We had an American native English proofread the paper once more.
And in the process, we have corrected few error and add information in ABSTRACT as well.
Thank you once again.
Reviewer 2 Report
This study provides useful basic data on the improvement of aerobic capacity in adults with cerebral palsy. However, I think it is necessary to correct the appearance and careless mistakes of this paper.
Comments for author File: 
Comments.pdf
Author Response
Thank you for insight on the important part of my research.
We have correctly revised the manuscript where you have pointed out.
Thank you once again.
Reviewer 3 Report
Dear authors.
The existence of a significant correlation between muscle strength and aerobic capacity in people with reduced functionality of the locomotor system does not indicate that a low level of muscle strength affects aerobic capacity. Low physical activity, aging, many diseases or other factors can negatively affect both aerobic fitness, cardio-respiratory system efficiency, muscle strength and functionality. Therefore, the existence of a correlation between the level of muscle strength and aerobic capacity is a convergence, muscle strength does not affect performance, there is no basis to conclude as the authors do. Variables that are correlated may or may not be causally related. For example, if there is a high correlation between the length of the thumb of the right hand (cm) and the reading test score of elementary school students, it cannot be concluded that long thumbs affect students' reading skills. In practice, the reason of existing yhis correlation is the age of the students: older students read better and at the same time have longer thumbs - because they are older. Thus, in people with CP the existence of a correlation between muscle strength and aerobic capacity does not mean that muscle strength affects aerobic capacity, the factor that affect both muscle strength and aerobic capacity to be low is CP.
The fatal methodological mistake assuming that muscle strength is the cause of low endurance does not allow for a positive assessment of the article
Author Response
Thank you for insight on the important part of my research.
First, previous studies described in ‘Introduction’ report that the decline in muscle function and problems of CP have an adverse effect on posture and exercise ability. Based on these previous studies, we tried to draw conclusions of this study. And as you said, it is difficult to draw conclusions on the relationship between muscle strength and aerobic ability only by correlation, so the endeavor was to try to find the most influential parts through regression analysis.
In the past, we investigated CP low aerobic capacity by comparing it with Range of Motion. (You, J., & Yamasaki, M. (2015). Effect of Range of Motion on Aerobic Capacity in Adults with Cerebral Palsy. <International journal of sports medicine, 36(04), 315-320> As a result, it was concluded that respiratory problems and dysphagia in ankle stiffness and the neck are factors that adversely affect aerobic performance.
Of course, as you said, low muscle strength is not the only thing in CP that adversely affects aerobic performance. If you think of ordinary people, it may be a very erroneous result. However, studies on CP are so insufficient, compared to the occurrence of CP, because it is difficult to conduct experiment itself and to recruit subjects. Even in such situations, this study was conducted because it was thought to be of great significance in finding an efficient way to improve aerobic capacity by approaching from the kinematic point of view of CP. Also, we will soon conduct a study on CP how the increase in Range of Motion and the increase in muscle strength affect aerobic capacity to prove the causality of our study. We will add this into our conclusion.
We greatly appreciate your advice and we will continue to make great efforts for CP research under insufficient circumstances.
Thank you.
Round 2
Reviewer 3 Report
Dear authors
I stand by my previous opinion. In many diseases, especially neurological ones (including cerebral palsy), decreased functional efficiency is observed at the level of the circulatory, respiratory and muscular systems. For example:
de Groot S, Dallmeijer AJ, Bessems PJ, Lamberts ML, van der Woude LH, Janssen TW. Comparison of muscle strength, sprint power and aerobic capacity in adults with and without cerebral palsy. J Rehabil Med. 2012; 44 (11): 932-938. doi: 10.2340 / 16501977-1037
Balemans AC, Van Wely L, De Heer SJ, et al. Maximal aerobic and anaerobic exercise responses in children with cerebral palsy. Med Sci Sports Exerc. 2013; 45 (3): 561-568. doi: 10.1249 / MSS.0b013e3182732b2f
Therefore, I propose to deal with the development of rehabilitation methods for people with cerebral palsy that can improve both aerobic capacity and muscle strength. I consider the analysis of the correlation between muscle strength and aerobic capacity unfounded.
Regards
Author Response
Dear reviewer,
First of all, I agree with you 100% that cerebral palsy results in decreased functional efficiency of the nervous system, respiratory system, and muscle system.
We looked into the two papers you suggested. Among them, Groot et al. (2021) reported that adults with cerebral palsy had lower aerobic capacity than general adults through comparison and showed a strong correlation between strength, P30 and POpeak. Furthermore, regression analysis concluded that muscle strength may be the limiting factor in adults with cerebral palsy for activities involving the lower extremities, such as cycling.
Our study examined the relationship between lower limb muscle strength and aerobic capacity of adult with CP, not the general population, and regression analysis was conducted to find lower limb muscle factors that could be said to have a greater impact. The results were obtained from regression analysis, not just by performing correlation analysis. If you believe our findings are groundless, it is questionable whether the results of the preceding studies above, which show a very similar analysis method and do not contain the contents of the nervous system and respiratory system of cerebral palsy, are groundless.
In addition, Balemans et al. (2013) divided CP into GMFCS groups simply indicating the degree of disability to determine differences in aerobic and anaerobic motor responses between groups, which also do not include factors for decreased functional efficiency in the nervous, respiratory, and muscle systems. And, of course, if there was a group that could be compared in this study, the difference would have been compared through t-test or ANOVA and it would have been analyzed.
As we said from the beginning, we agree with your opinion 100%, and CP research is difficult to conduct and derive results, so we think it is necessary to proceed in various ways. As you mentioned, we will continue to conduct research on factors that positively affect CP in order to develop rehabilitation methods that can enhance CP muscle strength and aerobic ability, and we will make sure to prove causality based on the results of this study.
Two other reviewers who have reviewed the paper have acknowledged our research results, and the review has been completed by revising all the suggestions pointed out by them. There may be several shortcomings in the results of this study in your position, but I sincerely ask for your consideration with a wider and more generous mind.
Thank you.
