Objective
The objective of this study was to systematically investigate the effects of TCEs on blood glucose control in patients with prediabetes.

Search strategy:
Comprehensive retrieval of randomized controlled trials (RCTs) was carried out using PubMed, Cochrane Library, EMbase, China National Knowledge Infrastructure, VIP Database for Chinese Technical Periodicals, Wanfang Data Knowledge Service Platform, China Biology Medicine disc, Google Scholar and Baidu academic databases. The retrieval window ranged from the establishment of the database to December 2018, and references related to the included trials were searched without language restrictions.

Inclusion criteria:
The study included RCTs with a clinical diagnosis of prediabetes that was also treated with TCEs.

Data extraction and analysis:
Literature screening, data extraction and literature quality assessment were performed independently by two researchers. In the case of disagreement, a third party was invited to negotiate and make a decision. Standardized mean difference (SMD) was used to estimate the therapeutic effect. Meta-analysis was performed using Review Manager 5.3.5 and Stata 15.0. Heterogeneity was assessed using Q test and I2, and the source of heterogeneity was determined using Galbraith diagram and sensitivity analysis. A Q test resulting in P < 0.1 and I2 > 50% indicated significant difference and random effect model analysis was performed. Otherwise, a fixed effect model was applied. Begg’s and Egger’s tests were used to assess publication bias.

Results
Nine RCTs involving 485 participants were included in this study. The results showed that TCEs could reduce fasting blood glucose (FBG), 2 h blood glucose (2hPBG) and HbA1c in patients with prediabetes. The treatment subgroup showed that an intervention of 6 months had better results, while the Gongfa subgroup showed that the TCE Baduanjin yielded better results. (1) FBG: SMD = –0.73, 95% confidence interval (CI) [–0.97, –0.50], P < 0.00001; Baduanjin: SMD = –0.83, 95% CI [–1.13, –0.53], P < 0.00001; 6 months treatment: SMD = –0.73, 95% CI [–1.20, –0.26], P = 0.002. (2) 2hPBG: SMD = –0.75, 95% CI [–0.94, –0.57], P < 0.00001; Baduanjin: SMD = –0.62, 95% CI [–0.91, –0.32], P < 0.00001; 6 months treatment: SMD = –0.91, 95% CI [–1.39, –0.44], P = 0.0002. (3) HbA1c: SMD = –0.56, 95% CI [–0.89, –0.23], P = 0.00008; Baduanjin: SMD = –0.46, 95% CI [–0.83, –0.08], P = 0.02; 6 months treatment: SMD = –0.77, 95% CI [–1.24, –0.29], P = 0.002.

Conclusion
TCEs had positive effects in improving blood glucose levels in patients with prediabetes. Hence, TCEs may be of potential therapeutic value for patients with prediabetes, as an adjuvant therapy along with other treatments. Although the evidence suggests that the intervention is effective for 6 months, the mechanism of TCEs on glycemic control, the minimum exercise dose and their safety remain to be further studied.

Key words: Traditional Chinese exercises, PrediabetesBlood sugar, Glycemic control, Hemoglobin A1c, Systematic review, Meta-analysis