Feasibility and preliminary efficacy of the Muscle Movers program: A teacher-delivered intervention to support children's skills and participation in muscle-strengthening activity

Muscle Movers is a 6-week, teacher-delivered school-based intervention designed to support primary school children’s development of muscle-strengthening activity (MSA) skills. Children participate in moderate-to-vigorous intensity activities, as they would during usual PE lessons. The intensity of physical activity is assumed, but not formally assessed. The intervention includes three components: (1) A curriculum-aligned physical education (PE) program (1 × 45 mins/week), The PE program is structured around four foundational bodyweight exercises (‘Master Moves’) and supported by teacher and student resources including a handbook with lesson plans (designed specifically for this trial), skill cards outlining key skill criteria for perform the Master Moves, equipment pack (including cones, bean bags, bluetooth speaker, skipping ropes, balls, and fitness dice), and wall charts (1 x 'managers' chart for allocating students as 'helpers' to carry/set up equipment, and 1 x 'motivators' chart to publicly recognise students' demonstration of 'self-management' and 'interpersonal' skills, as outlined within the NSW K-10 PDHPE syllabus). Week 1 introduces students to all four Master Moves (i.e., Scorpion squat, Lemur Lunge, Python plank and Panther Push-up), weeks 2-5 focused on each Master Move individually in sequence, and Week 6 aims to consolidate students’ understanding of all Master Moves. PE lessons follow a format comprised of three parts: i) Start Strong, a fun/simple warm-up activity; ii) Main Muscles, the main body of the lesson focused on the allocated Master Move, involving explicit skill instruction, a short individual challenge activity, and a game-based skill application activity; and iii) Muscle-Up, a separate activity to add further variety. To address common barriers, PE lesson activities are intended to be simple to organise and explain, engaging for children, and able to be delivered with limited space and equipment. The Main Muscles lesson segment uses familiar minor games, adapted to incorporate fitness infusion (i.e., the inclusion of vigorous exercise, in our case via the Master Moves, in the context of game play). Teachers receive initial modelling of lesson delivery by a researcher in week 1 but independently deliver the program thereafter. The intervention is aligned with the NSW PDHPE curriculum and informed by behaviour change and pedagogical frameworks to promote skill development, engagement, and autonomy in a primary school setting. (2) Classroom-based MSA energiser breaks (2 × 5 mins/week). Teachers deliver weekly movement breaks in the classroom on days the PE lesson is not being delivered. There are two 'styles' of energiser breaks: 'Would you rather' breaks are based on a distinct theme (e.g., food, occupations etc) and present students with two options to select from. Students chose which option ‘they’d rather’ and perform a corresponding exercise depicted on screen for 20 seconds (or until volitional failure). 'Rock, paper, scissors' breaks are based on the classic game, with students aiming to beat the result displayed on screen. After physically presenting their choice, one of the options is displayed on screen and students determine whether they won, lost or drew the round. They then perform an exercise corresponding with the appropriate outcome for 20 seconds (or until volitional failure). Each energiser includs five rounds and takes just under five minutes to complete. The breaks are teacher facilitated but supported by electronic resources (i.e., Microsoft PPT files) diplayed using a projector or smartboard. Slide transitions are pre-programmed so the teacher can simply press play, and then focus on encouraging students, and promoting correct exercise skill execution, rather than modelling all exercises. (3) Active homework tasks (1 × 10 mins/week). Students complete 1 weekly home task, designed to facilitate self-directed practice of the 4 x Master Moves outside of the school setting, and supported by a hard copy student handbook. The student handbook includes six distinct activities. Example tasks includ: i) guessing the number of repetitions of a selected exercise that could be completed in a given timeframe and comparing guess with result, ii) selecting a song with a repetitive lyric and performing a self-selected exercise each time the lyric appeared when the song was played, iii) teaching a family member how to complete a self-selected Master Move by providing a demonstration and giving feedback using the information on the skill card within the handbook, iv) selecting household chores, allocating exercises to each, and completing self-selected repetitions to indicate to caregivers when the chore was completed, v) searching within home reader for words that rhyme with Master Moves and completing a repetition of the corresponding exercise when found, and vi) locating facts corresponding to the animals linked to Master Moves and completing repetitions after recording the fact in the handbook. Teacher monitoring of adherence: Teachers log their completion and rate their satisfaction with each of the PE lesson activities within the teacher handbook. The handbook is returned to the research team to ascertain teachers' completion of the PE lesson activities. Teachers report the number of weekly energiser breaks they facilitate, and also report the number of homework tasks assigned, and an estimate of the proportion of children that complete the assigned homework tasks.