Table 4 Description of the outcome measures

Primary outcome: FMSs

Gross motor skills

Evaluated using The Test of Gross Motor Development-Third Edition (TGMD-3) which has been validated in China with satisfied reliability [76]. The TGMD-3 includes two sub-scales, the locomotor skill sub-scale composed of six skills: run, gallop, hop, horizontal jump, slide (judged on four performance criteria) and skip (judged on three criteria), and the ball skill sub-scale (previously named object control skill in the TGMD-2) composed of seven skills: one hand forehand strike of self-bounced tennis ball, kick a stationary ball, overhand throw, underhand throw, two hand strike of a stationary ball, one hand stationary dribble and two hand catch. Before the assessment of each skill, an accurate verbal description and demonstration of each skill was carried out by a trained researcher. Each child completed three trials, one for practice and then two formal trials. Only the scores of the two formal trials were recorded for the evaluation. Children’s performances were observed and evaluated following 3 ~ 5 qualitative performance criteria for each TGMD-3 assessment skill: every criterion was scored 1 point (present) or 0 point (absent) using process-oriented checklists [77]. The total score for each item is given by the sum of both trials. Items' sums were used to calculate the score for the locomotor (46) and ball control skills sub scales (54) as well as for the overall TGMD-3 scores (100) [77]

Manual dexterity and balance

Assessed using a subscale of the Movement Assessment Battery for Children-Second Edition (MABC-2, band 2 and 3) [78], which has demonstrated good reliability and validity in Chinese children [79]. Manual dexterity, which is composed of placing pegs, threading lace and drawing trail 2. Balance, which includes one-board balance, walking heel-to-toe forwards and hopping on mats. The scoring was consistent with the method published in the movement ABC-2 UK manual [78]

Secondary outcomes

Health behaviors: PA, sedentary behavior, and sleep

The ActiGraph GT3X + accelerometer (ActiGraph LLC, Pensacola, FL, USA) will be used to objectively monitor whole-day PA. All participants will be asked to wear a monitor at the waist on an elasticized belt at the right midaxillary line. Participants were encouraged to wear the accelerometer 24 h per day (removing only for water-based activities: i.e., swimming/bathing) for at least 7 d, including two weekend days. Days with > 16 h/d of activity recordings (from midnight to midnight) were considered as valid [80], and the minimum amount of non-sleep data that was considered acceptable for inclusion was at least 4 days with at least 10 h of wake wear time per day, including at least one weekend day [81]. Data were collected at a sampling rate of 80 Hz downloaded in 1-s epochs with the low-frequency extension filter using the ActiLife software version 6.13 (ActiGraph LLC) and reintegrated to 15-s epochs for analysis. Non-wear time will be defined as a period of 20 consecutive minutes or more zero counts [82]. Night sleep duration was calculated in R software using GGIR package (version 2.0) default algorithm, as described by Van Hees et al. [83]. Evenson cut-off points [82] will be applied to determine non-sleep time spent in light (25–574 counts/15-s), moderate (574–1003 counts/15-s) and vigorous PA (> 1003 counts/15-s), and total sedentary time as all movement ≤ 25 counts per 15 s. Parents will be instructed to fill in sleep logs for their child with the purpose of cross-validating the waking (wear) time

Physical fitness

Assessed using the revised 2014 version of the Chinese National Student Physical Fitness Standard (CNSPFS) [84], involving a total of 11 physical fitness indicators. The 7 described below are suitable for primary school students, including BMI, vital capacity, 50 m sprint, Sit and reach, timed skipping rope, timed sit-ups (just Grades 3–6) and 50 m × 8 shuttle-run (just Grades 5 and 6). Following the guidelines, test examiners conducted each test per a protocol determined a priori. Each fitness indicator score was weighted by a grade- and sex-specific percentage

Perceived motor competence

Assessed using the subscale (athletic competence) of the Self-perception Profile for Children (SPPC) [85]. Athletic competence subscale of SPPC includes 6 items, three of the items are worded such that the first part of the statement reflects low competence or adequacy, and three are worded to first reflect high perceptions of competence or adequacy. This counterbalancing is reflected in the scoring of items, where half of the items are scored 1, 2, 3, 4 and half are scored 4, 3, 2, 1. This is to insure that children are tracking the content of the items and are not simply providing random response choices or are always checking the same side of all questions. In addition, the Chinese version of the SPPC has adequate reliability, ranging from 0.61 to 0.76 [86]. The structure and criterion validity are acceptable [87]

Perceived well-being

The Chinese version of the 12-item Psychological Well-Being Scale for Children (PWB-C) will be used [88, 89]. PWB-C contains six dimensions of psychological well-being: environmental mastery, personal growth, purpose in life, self-acceptance, autonomy, and positive relations with others. Options were given on a 4-point Likert scale, ranging from 1 (“almost never”) to 4 (“very frequently”). The mean score of the 12 items will be calculated, with a higher score indicating a higher level of perceived well-being

M-PAC components of PA for both parents and children

The Chinese translated items of M-PAC components of PA will be used [90,91,92]. The questionnaire package includes measures for behavioral intention, instrumental and affective attitudes, perceived capability, perceived opportunity, parental support (intentional and actual), action planning and coping planning, action control, habit strength, and identity. The response options and scoring approach will be consistent with the settings in previous studies [65, 66, 90, 91]

Anthropometric and body composition measures

Height and weight will be measured calibrated medical digital scales (RGT-140, Changzhou, China) and portable stadiometer (GMCS-I, Beijing, China) to the closest 0.05 kg and 0.1 cm, respectively following a standardized protocol [84]. Waist circumference will be measured using a flexible plastic tape at 1 cm above the umbilicus from the horizontal level in a standing position, at the end of a normal expiration [92]. Each of aforementioned anthropometric indexes was measured twice and the mean value was used for data analysis. A Bio-Impedance Analysis (BIA) was conducted using Portable body composition analyzer (InBody230, Seoul, South Korea) and Lokin Body 120 software (DMS-BIA technology; InBody Co., Seoul, South Korea) to estimate body composition, including percent of body fat (PBF), fat mass (FM), fat-free mass (FFM, kg) and skeletal muscle mass (SMM, kg). The instrument was validated against dual-energy X-ray absorptiometry for school-age children with satisfactory results for estimating body fat [93]

Additional information

Demographics

Children’s age, gender, grade (primaries 1–6), ethnicity (Han or others), parental educational level (below college; college or above) and yearly household income (low: RMB < 84,000; medium: RMB 84,000 – 132,000; high: RMB > 132,000) [60] will be reported by parents