Study design and population
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We conducted a double-blind, randomized controlled trial (RCT) study from October 2020 to January 2021 using randomization, assignment concealment, and blinding methods (ClinicalTrials.gov identifier: NCT04830059. Data: 02/04/2021). Ninety-three participants met the inclusion criteria and were randomized into three groups: HIIT (N = 32), MICT (N = 33), and control (N = 28). Demographic information was collected, including age, gender, height, weight, family income, education level, and birthplace (rural or urban). Each participant had a unique identification number. They were randomly divided into different groups using a random number generator. The randomization process was carried out by a research staff member who did not participate in the assessment and analysis of the data. Group allocation was confidential to ensure the successful implementation of randomization. The participants’ identification number and grouping information were hidden in an opaque envelope, which was opened by themselves after the baseline assessment. Moreover, participants in the three groups came to the fitness centre on different days of the week, so they did not know the existence of other groups. Participants and evaluators were blinded to the group allocation of intervention assignments throughout the study. Detailed information on the randomization, assignment concealment, and blinding methods is described in the previous articleThe sample size was calculated by the software of G-Power (Version 3.1.9.7). The effect sizes of exercise interventions on cognition ranges from 0.19 to 0.59 according to the previous studiesThe CONSORT flow diagram. This study was conducted in accordance with the International Conference on Harmonization guidelines for Good Clinical Practice and the Declaration of Helsinki. The academic ethics committee of Tsinghua university approved this study (IRB 20190091). All participants provided written informed consent prior to participation.