The overview will follow the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement for improved reporting (13). The protocol for the overview was registered in the international prospective register of systematic reviews (PROSPERO registration number: CRD42021248444).
Relevant systematic reviews and meta-analyses will be obtained from the following database: PubMed, Cochrane Database of Systematic Reviews, Embase, and Web of Science Core Collection. The retrieval time spans from the establishment of the database to June 2021. Furthermore, a snowball searching for the reference of relevant meta-analyses will also be performed. Search terms will be included combinations of MeSH terms and text words, as described in Table 1. Article language will be restricted to English.
The inclusion criteria are: (1) included patients diagnosed with chronic disease, e.g., cardiovascular disease, cancer, chronic obstructive pulmonary disease, diabetes mellitus, chronic kidney disease, Alzheimer disease, Parkinson disease, osteoarthritis, chronic liver disease, chronic fatigue syndrome, fibromyalgia, et al.; (2) compared traditional Chinese exercise with usual/standard care; (3) systematic reviews with meta-analyses of intervention trials; (4) outcome-based on cardiopulmonary fitness, muscle strength, muscle endurance, body composition, and HRQoL. Systematic reviews with meta-analyses of observational studies will be excluded; conference abstracts, case reports, comments, and experimental animal studies will also be banned.
Two independent authors will scrutinize the titles and abstracts from the search results. Then full-text articles will be read for a complete assessment and determination of inclusion or exclusion. If necessary, disagreements will be resolved through discussion to reach a consensus or involve a third reviewer.
The following data from each meta-analysis will be extracted and tabulated: publication details (author and year), diseases type, description of outcome measures, number of included studies and participants, risk of bias assessment, exercise-related adverse events, and outcome-specific standardized mean differences (SMDs) or mean differences (MDs) with corresponding 95% Confidence Intervals (CIs).
The methodological quality of each included systematic review and meta-analyses will be evaluated using the A Measurement Tool to Assess Systematic Reviews (AMSTAR) tool (14). This scale includes a total of 11 items, each with a "yes" (1 point), "no" (0 points), "cannot answer" (0 points), or "not applicable" (0 points) (Table 2). According to the final score, 0–4 indicates low quality, 5–8 indicates moderate quality and 9–11 indicates high quality (15).
Quality of evidence
The overview will use the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system to evaluate the quality of evidence of outcomes (16). The quality of evidence for each outcome will be classified as high, moderate, low, or very low based on the evaluation for study design, risk of bias, inconsistency, indirectness, and imprecision. See Table 3 for a further description of the GRADE system.
For each outcome, the data will be analyzed qualitatively based on the SMDs or MDs. The authors will extract data from original randomized control trials and process as instructed by the Cochrane Collaboration if data are insufficient. The level of heterogeneity will be evaluated with Q2 statistic and I2 metric (≤25% indicate low heterogeneity, 25%< I2≤50% indicate mild heterogeneity, 50< I2≤75% moderate heterogeneity, >75% indicate high heterogeneity) (17).