Study Design
The study described in this paper evaluated an aerobic walking intervention conducted among young adults. The walking was not a self-selected speed as many walking interventions did, but with two basic speed requirements: a. continually walking for at least 10 minutes; b. walk at least 60 steps per minute. Walking for one hour per day in the requested speed was obligatory, which was the so-called daily aerobic walking intervention. Participants were assigned into two groups randomly (i.e., intervention group and control group). The intervention period of the study was four weeks continued with four weeks follow-up, which in total, was eight weeks. A battery of online questionnaires measuring sleep quality, stress status and life satisfaction were sent to all of the participants at the baseline of the intervention (pre-intervention), after intervention (4 weeks later) (post-intervention), and at follow-up (8 weeks later). The intervention study was approved by university ethical committee (registration code: 2018/421).
Intervention
The participants in the intervention group performed daily aerobic walking (DAW) for 60 minutes (in reality, 50–60 minutes are acceptable), and the participants in the control group were in the waiting list and were asked to maintain sedentary lifestyle. Both of the two group members were asked to avoid any additional physical exercise programs during the intervention period. The DAW was tracked by pedometer and daily diary. Omron HJ-112 (Omron Corporation, Kyoto, Japan) pedometer was used to track the daily walking activity.
Participants in the intervention group were asked to complete a 60-minute DAW daily and record the data (e.g. total steps, aerobic steps, starting time, ending time, miles, calorie expenses) from the pedometer to the dairy sheet. The advantage of the using this pedometer is that it could differentiate normal walking and aerobic walking as requested in the experiment. Participants were orientated about how to use and set the pedometer before starting the intervention. Participants were encouraged to carry out the intervention for 4 weeks, but each participant could have 3 days off in case of bad weather, illness, emergency etc.
The online questionnaires were formulated by Qualtrics, and were sent electronically to the participants via anonymous link. All participants have signed the written consent form before joining the study. The daily routine of the participants was not interrupted except the 60-minute DAW. The participants in the intervention groups were requested to send the aerobic walking steps and walking time to a research assistant, which served as a way of controlling the walking performance of the participants and data collection as well.
Participants
Participants were recruited by advertisement through both electronical and printed posters. The electronical posters were posted on social media platform (e.g. Facebook, WeChat etc.). The printed posters were posted on the information bulletins in Eötvös Loránd University, Hungary. People who are interested in the study were welcomed to contact the first author by email or WhatsApp. Text or phone-call interviews were organized with each contacted volunteer to assess the eligibility of the contacted people. Despite the demographic information (e.g. age, health status, general life routine etc.), we screened the volunteers with two questions (1. Do you participate in any kind of regular exercise programs (weight-lifting, walking, running, swimming etc.)? 2. Are you involved in any physical or sport teams?) in order to roughly assess their sedentary life status.
After screening, 54 participants met the inclusion criteria (both answers were “NO” for the above two screening questions), and 27 participants were assigned to intervention group and 27 to the control. The grouping was done by lottery method. All the participants in both groups were equipped with pedometers to record their daily steps, calories expenses, miles etc. The demographic characteristics of the participants are presented in Table 1. Participants who failed to complete the questionnaires did not mean they dropped off from the intervention. The quality of the intervention process was controlled by pedometer and diary sheet and one research assistant recorded the walking figures from each participant in the intervention group every day. The age range of the participants was 19 to 36 years old, and the mean body mass index (BMI) was 22.46 (SD = 3.10).
Table 1
The description of the participants
| Intervention group | Control group |
| n | Range | Mean ± SD | n | Range | Mean ± SD |
Age | 21 | 19–36 | 23.38 ± 4.58 | 25 | 19–35 | 24.08 ± 5.13 |
Gender | 24 | 10 males | 14 females | 27 | 9 males | 18 females |
BMI | 24 | 18.73–30.43 | 22.87 ± 2.63 | 26 | 17.38–31.80 | 22.88 ± 2.63 |
Study/Work | 21 | 20 study | 1 work | 24 | 21 study | 3 work |
Note: BMI Body Mass Index |
Please insert Table 1 about here.
Measurements
We used Pittsburgh Sleep Quality Index (PSQI),11 which is a self-report scale to assess sleep quality and sleep components for the past month. The scale contains 19 items, which are grouped to evaluate seven sleep components including (1) sleep duration, (2) sleep efficiency, (3) sleep latency, (4) daytime dysfunction due to sleepiness, (5) sleep disturbance, (6) sleep medication use, and (7) subjective sleep quality. The component score ranges from 0 to 3, a sum of seven sleep components’ score is the global sleep quality (ranges from 0–21). Higher score indicates poorer sleep quality. The borderline of good sleeper and bad sleeper is 5. A score over 5 indicates bad sleeper, while a score less than 5 (or equals 5) indicates good sleeper.
The Perceived Stress Scale (PSS) by Cohen12 is recognized as the most widely used psychological instrument to measure perceptions of stress. It measures the degree to which situations one is appraised as stressful. The items were designed to discover how unpredictable, uncontrollable and overloaded people find their life to be. There are two version of the PSS: the long-version with 10 items, and short version with 4 items. In the present study, we adopted the short version to assess the stress of the participants.
Satisfaction With Life Scale (SWLS) is a 5-item instrument to measure cognitive judgments of one’s life satisfaction. Respondents point out how much they agree or disagree with the 5 statements about life by using a Likert scale that ranges from 1 (strongly disagree) to 7 (strongly agree). SWLS is designed to assess respondents’ life as a whole, which does not assess domains such as health or finances. The total score climes from 5 to 35, which was grouped into seven categories ranging from extremely dissatisfied to extremely satisfied. Statistical Analysis
In line with the first aim of the study, we used independent t-test to show the intervention outcomes regarding to sleep quality, stress and life satisfaction. Linear regression was used to predict the covariant effect of age, gender and BMI, which can be potential confounders. The difference between post intervention and baseline for those main variables (i.e. PSQI, PSS, SWLS) were used as dependent variables. For the second aim of the study, repeated analysis of variance ANOVA manures was applied to disclose the longitudinal effectiveness of DAW exercise on sleep quality, stress and life satisfaction among young adults.
Considering the missing data and drop-off of participants, we selected only those who both completed the intervention and completed the questionnaire assessment for statistical analysis. The rigorous data sortation reduced the potential bias caused by the drop-outs (reasons for drop-off are presented in the limitation section below). The diary sheet records were utilized as filters. Eventually, we got 13 participants from the intervention who adhered to the intervention process and follow-up and 17 participants in the control group who were consistent with the study. Statistical analysis was performed by SPSS version 21.0, of which the statistical significance level was set at 0.05.