The development of a Rasch measurement physical fitness scale for Hong Kong primary school-aged students

The main purpose of this study was to develop a Rasch Measurement Physical Fitness Scale (RMPFS) consisting of the physical fitness indicators routinely used in Hong Kong primary schools. Data used in this study were retrieved from the database of a Hong Kong primary school covering students’ physical fitness data over academic years 2002-03 to 2006-07. The indicators of physical fitness include Body Mass Index (BMI), 6-minute Run, 9-minute Run, 1-minute Sit-ups, Sit-and-Reach, Right Handgrip, Left Handgrip, Standard Push-ups, and Modified Push-ups. Each indicator reflects one of the five usually recognized components of physical fitness: body composition, cardiorespiratory fitness, flexibility, muscular strength, and muscular endurance. After data cleaning, a total of 9,439 student records were used for the Rasch scale development. Following a series of iterative Rasch analyses, a RMPFS integrating three key core components of physical fitness (i.e., cardiorespiratory fitness, muscular endurance, and muscular strength) was developed successfully. The RMPFS and its scale indicators showed fit to the Rasch model sufficient for the intended purposes of measuring overall fitness of children and tracking fitness levels over time. The RMPFS measures were then used to display Hong Kong primary school-aged students’ overall physical fitness levels and developmental trends effectively, and the percentile distributions of overall physical fitness, measured by the RMPFS, for age, height, weight, and BMI were illustrated graphically for the sample of students in this research. Compared to traditional approaches to measurement in physical fitness, this Rasch calibrated physical fitness scale has the following advantages. The first, the Rasch measurement logit scale provides interval measures that have consistent and stable meaning regarding the distances between persons or items, therefore, facilitating meaningful comparisons. The second, the RMPFS provides sample-distribution free and item-distribution free measures. The third, the RMPFS developed in this study can calibrate primary school-aged students’ overall fitness levels on the common scale if students had performed on any one physical fitness indicator from among those calibrated into the scale. The successful development and application of the RMPFS provides strong evidence of the benefits derived from the techniques used in this research, so that physical fitness data can reflect students’ physical fitness more objectively. Major implications for physical education practice include dividing students into groups based on fitness levels rather than sex in PE classes. Although BMI is not an appropriate indicator of overall physical fitness, height and weight are appropriate moderate correlates of overall physical fitness. Moreover, the existence of considerable individual differences in overall physical fitness at any one grade level justifies the necessity of developing appropriate fitness programmes that accommodate students’ individualized requirements and reminds teachers to cater for students’ individual needs in PE classes. This research also provided practical value to the partner school with regard to its PE programmes. The findings of this study will be informative to physical education teaching practice and policy making by providing a better knowledge basis for interpreting physical fitness assessment results and giving appropriate feedback to students. The limitations of this study are related to the large measurement errors for RMPFS person estimates such that overall physical fitness estimations at the individual level have measurement errors too large to allow almost any meaningful distinctions to be made between individuals. The overall physical fitness measures and changes at the group level are more precise and, therefore, informative for depicting students’ physical fitness development. Future research could attempt to find solutions to reduce the measurement error of person estimates such as developing and calibrating new physical fitness indicators into the Rasch scale.