2.7.3. Subgroup analysis and sensitivity analysis

We need to solve heterogeneity because it is only when the included studies have the least heterogeneity, the credibility of the synthesized effect size is high, and sensitivity and subgroup analyses are the most common approaches used to solve heterogeneity. If the results of meta-analysis are positive and the number of included studies is over 3, we will analyze the sensitivity using STATA 15.0 software. The sensitivity analysis is performed by excluding study one by one. The sensitivity is low and the results are of stability and reliability if there are no significant changes that appear in the results before and after the exclusion; if not, it indicates a high sensitivity and unstable result. And in this study, year of publication, country of corresponding author, type of study design, mean age, training intensity, and length of exercise-training time will be considered and designed for subgroup analysis to find the possible significant heterogeneity.