Participants
Participants were working women randomly recruited from eight communities in Shanghai China using the stratified cluster sampling method. Participants were either friend-referrals or self-referrals based on advertisement and recruitment events in communities. They were gathered in the Sports Health Service Center of Shanghai University of Sport for screening. The sampling inclusion criteria were: aged 25 to 60 years, Shanghai residents, not retired, without joint or muscular abnormalities, and having the ability to participate in exercise and complete the health outcomes questionnaires. A total of 70 participants were needed for this study to reach a power of 80% at an alpha level of .05 based on a statistical power analysis to detect an effect size of ES = 0.25 [32].
A total of 225 individuals initially displayed an interest in participating in the study. Of them, 135 completed the baseline measures and were randomized into three groups: group-based intervention group (Exp_G, n = 46), individual-based intervention group (Exp_I, n = 44), and control group (Ctrl, n = 45). The participants in the group-based intervention group were randomly allocated with each group of 6-8 women. Of the 135 randomized participants, an additional 14 participants were lost at the 12-week follow-up. Five participants dropped out from lack of interest, and four dropped out because of schedule/time conflicts. In addition, five cited family/personal issues that prevented continuing participation. Finally, 121 working women who met the inclusion criteria were enrolled in the study and completed the pre- and post-measures (Fig. 1). This study obtained the approval of the ethics committee at Shanghai University of Sport. All participants signed consent forms before they joined the study and were provided a full explanation regarding the purpose and potential benefits/risks of the study, confidentiality, and their right to withdraw from the study.
Fig. 1 Participant flow through the study
Measures
Demographic variables
To characterize the participants in this study, self-reported personal information on age and race were obtained using questionnaires.
Stress
The Chinese version of the Psychosomatic Tension and Relaxation Inventory (PSTRI) was used to measure stress [33]. This inventory consists of 50 items rated on a Likert scale from 1 (never) to 5 (always). The total score on the 50 items was used to measure the level of perceived stress. Higher PSTRI scores indicated higher levels of stress. In this study, the Cronbach’s alpha of this scale was .95.
Burnout
Job burnout was measured by the 15-item Maslach Burnout Inventory-General Survey (MBI-GS) developed by Maslach and Jackson [12]. The survey consists of three dimensions: emotional exhaustion (5 items), professional efficacy (6 items), and cynicism (4 items). All the items were rated on a Likert scale from 1 (never) to 7 (every day). Lower scores on the dimension of professional efficacy and higher scores on the dimensions of cynicism and emotional exhaustion denoted higher levels of job burnout. The Chinese version of the MBI-GS was translated back into English to test language validity. The Chinese MBI-GS exhibited good reliability and validity and was widely used in Chinese populations [34]. In this study, the Cronbach’s alpha coefficient for the total scale was .71. The Cronbach’s alpha coefficients of emotional exhaustion, cynicism, and professional efficacy were .86, .79, and .90, respectively.
HRQoL
HRQoL was measured by the Chinese version of the Quality of Life Scale-Brief [17], which was modified from WHOQOL-100 and translated into Chinese. The scale consists of 26 items and includes four dimensions: physical health, social relationships, psychological status, and environment. Each item was rated on a five-point Likert scale (1 = very dissatisfied; 5 = very satisfied). Item scores for each dimension were coded/recoded and summed to obtain the total HRQoL score, with a higher total score indicating a better quality of life. In this study, the Cronbach’s alpha coefficients of physical health, psychological, social relationships, and environment were .76, .72, .75, and .79, respectively.
Procedure
The participants who signed the consent form were directed to the Sports Health Service Center of Shanghai University of Sport to complete the physical fitness tests and baseline self-reported questionnaires on work stress, burnout, and HRQoL. All the devices for physical fitness tests were from TKK Company of Japan, except for the devices for Bone Mineral Density (BMD) and VO2Max tests. BMD was measured at the femoral neck, total hip and lumbar spine L1–L4 using dual-energy X-ray absorptiometry (DXA) (Lunar Prodigy, GE Lunar, Madison, USA). TheVO2Max test was performed on a treadmill which began with a warm-up running for 5 to 10 min followed by an incremental running test until volitional exhaustion. The participant was equipped with a breath mask that covered the nose and mouth and a heart rate monitor worn on the chest. Oxygen uptake was measured using an indirect calorimeter (COSMED, Trentino, Italy). Subsequently, the participants were randomly assigned to one of three groups: group-based intervention (n = 41), individual-based intervention (n = 40), or waitlist control (n = 40). Randomization was completed by an independent investigator who was not involved in data collection or intervention delivery. For all groups, follow-up data were collected in the same manner as the baseline data immediately after the three-month intervention. During the 12-week study duration, the control group did not receive any specific instructions relative to physical activity (i.e., they were free to continue their regular routines and exercise if they wished). This study was approved by the study venues.
Intervention
In our study, there were four intervention-related variables: intervention type, intervention frequency (i.e., times per week), the number of weeks, and the hours per session. The latter 3 variables were considered as indexes of the intensity of the intervention. Two different exercise interventions were involved: (1) an individual-based intervention delivered in an individual format and (2) a group-based intervention delivered in a group format.
The intensity of the individual exercise intervention group was three times per week for 45-60 min per session. The goal for each participant was 150 min of physical activity per week with moderate intensity. Each exercise program was individualized according to baseline health, fitness levels, and personal goals. Three parts were included in the individual exercise program: warm-up, cardiovascular training (cycling, cross-training, brisk walking), and a cool-down period. The group exercise cohort also exercised three times per week for 45–60 min per session, with a similar target goal of 150 min per week of moderate intensity physical activity. The group exercise program also consisted of three parts: warm-up, cardiovascular training (cycling, cross-training, brisk walking), and a cool-down period. Although they participated in the same exercise activities, group-based intervention group held team-focused activities, such as competitions among different groups or tasks that needed to be done together, thereby helping to foster team cohesion. All exercises were led by the same accredited exercise instructors.
The principle of counselling intervention was client-centered, which means all the activity launched was based on the needs of each participant. Facilitating disclosure of feelings and anxieties, clarifying issues and providing reassurance and support for the women as required were the duty of the counsellor. The individual and group counselling interventions were both conducted once a week for one hour, and the group counselling intervention was in groups of six to eight women. General themes covered were the following: work-family conflicts, stress, burnout, anxiety, self-efficacy, and health-related quality of life. The counselling happened at the end of the third exercise intervention every week. In the study period of 12 weeks, there was no specific exercise or counselling that participants in the control group needed to engage in.
Data Analysis
The data were analyzed using Statistical Product and Service Solutions (SPSS 22.0, SPSS Inc.) software. Descriptive statistics were calculated for all variables. Data normality was verified by using the Kolmogorov-Smirnov test. Multivariate analysis of variance (MANOVA) with repeated measures was performed between different groups to examine differences at baseline and after the 12-week intervention. To account for multiple testing, Bonferroni corrections, with adjusted CIs, was performed to investigate the differences between groups. An alpha level of .05 was used to determine statistical significance. Effect sizes (ESs) were calculated utilizing the mean and standard deviation (.2 or less is a small ES; approximately .5 is a moderate ES; .8 or more is a large ES) [35].