This section will be presented in two phases (See Figure 1). Phase one will provide a description of the PERF-FIT and explain the steps taken to develop the test items. In the second phase, we will provide preliminary evidence to support the validity and feasibility of the test.
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Phase 1: Test description and development
Description of PERF-FIT
The PERF-FIT was designed as an instructor-administered, cross-culturally comparable, functional measure of skill-related physical fitness for children aged 5-12 years. The main rationale was to develop a low-cost, and easy-to-administer measure that could be used across a variety of low-income contexts. The PERF-FIT focuses on skill-related physical fitness and is divided into two subcomponents; motor performance, and agility and power subscales.
Motor performance subscale.
The motor performance component or the skills item series (SIS) consists of five items including jumping, hopping (left and right), bouncing and catching, throwing and catching, and balance. These tasks are administered to the child in an increasing order of difficulty (task loading). The child starts at the easiest level and ends at the most difficult level within the same task series. The items within a particular task/skill series are terminated when the child is unable to achieve the minimum points after two consecutive trials. No second trial is performed when the maximum points are attained. For example, in the jumping task series, distance and height are modified to increase the difficulty level of the task after the initial trial. Each child is given a practice trial before performing the test trials. To avoid fatigue 15 seconds rest is allowed between trials. The child’s performance during the test trials are recorded and used for calculating the item score (See additional file A for items and scoring).
Agility and power subscale.
The agility and anaerobic power component has five items. These are running, stepping, side-jump, long jump, and overhead throw. All items are initially demonstrated before the child is asked to perform one practice trial. Following this, each child is expected to perform two test trials, with 15 seconds rest interval. The child’s performance during the test trials is recorded and best scores are used in the analysis.
Developmental process
The development of the PERF-FIT involved a three-step process and included (1) development of a conceptual framework (2) selection of initial item set and expert evaluation and (3) pilot testing.
Conceptual framework.
A literature search was first conducted to define the domains of skill-related physical fitness that were thought to be important for children’s development and growth. Based on our search, six key skill-related physical fitness attributes were identified and defined. These included agility, power, balance, coordination, speed and reaction time (Table 1). The outcomes of the chosen items are product-oriented in order to test the quantitative level of performance in tasks that are considered to be basic skills of children at elementary school age.
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These domains were selected because of their cross-cultural applicability, relevance to childhood routines and games, ease of testing in low-income schools and their ability to enhance physical activity across the lifespan. In addition, we wanted to ensure that the relationship between (anaerobic) fitness and motor skills is acknowledged in diverse low-income communities [24] and to create more awareness that evaluation of skill-performance related physical fitness has important implications for child development, active lifestyle, physical education and policy development [25].
Item identification.
Based on the literature search and pre-defined criteria (see Table 2), twenty items representing the six core domains of the theoretical framework were identified and reviewed by a panel of experts (experienced researchers and practitioners). Based on the experts’ feedback, ten items were finally included in the PERF-FIT test battery. The ten items were divided into two subscales as mentioned earlier (i.e. motor performance and agility and power components). Since most items have a start signal to which the child has to respond no separate reaction time item was included. The theoretical and operational definitions of each domain were clarified to guide task identification (See table 1). Further, the process of increasing the difficulty of tasks (task loading) for each item was defined to facilitate implementation and interpretation of scores. (See Additional file 2 for the items and the increase in difficulty).
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Pilot testing.
The last stage of the development of the PERF-FIT was the pilot-testing phase. The final items were tested in two small samples involving South African children (n=10 and n=20) to assess feasibility, acceptability, ease of administration and implementation challenges. Feedbacks provided by the children and test administrators were used to refine aspects of the test items, and to improve the clarity of the instructions and scoring forms. These were done to reduce the burden of administration (for an example of an item description see Additional file 2). Instructions for obtaining the standardized materials were also provided in the manual (see Additional file 3).
Phase 2: Validation
Content validity
Seven experts (i.e. four pediatric physical therapists, one occupational therapist, and two physical educators) with several years of experience in movement skills and fitness assessments were asked to assess the relevance of the PERF-FIT items. Each expert had experience in test development and had worked with children in low-resource settings for more than ten years. According to the COnsensus-based Standards for the selection of health status Measurement INstruments (COSMIN) guidelines
a moderate sample size (5-9 experts) is rated as good to assess if all items are relevant for the study population (content validity) [26]. Experts were required to indicate whether the PERF-FIT items reflected the constructs they were intended to measure. In addition, they were asked to evaluate the appropriateness of the selected tasks for the target population for the intended future use of the test (typically developing children and children with poor motor coordination, e.g. Developmental Coordination Disorder (DCD), Attention Deficit Hyperactivity Disorder (ADHD), or Fetal Alcohol Syndrome (FAS) Learning Disabilities (LD), in low-resourced communities). This evaluation was done using a 4-point scale developed based on the criteria proposed by Davis [27] (Score 1 = not relevant, 2 = somewhat relevant, 3 = quite relevant, 4 = highly relevant). The Content Validity Index (CVI) was used as an estimate of the content validity of each variable in the test battery. Additionally, Scale-level Content Validity Index (S-CVI), representing the overall content validity of the PERF-FIT, was computed as the average of the I-CVIs for all the test items [28].
Feasibility
The feasibility of the test was assessed by looking at 1) acceptability (based on participants and assessors’ perspectives), 2) adverse events or injuries 3) burden of administration - set up and administration time, cost, equipment, space and training requirements. The experiences of the assessors were also captured by self-report.
Structural validity
The PERF-FIT test was validated in a convenience sample of 80 Brazilian children aged 7-12 years (mean 9.2 SD 1.1). Following the COSMIN guideline in sample size 80 children was deemed acceptable for this kind of study [26]. Participants (39 boys; 41 girls) were recruited from two primary schools in a low-socioeconomic area in the state of Sao Paulo. Children were excluded if they had any injury or physical disability that hindered their involvement in the assessments. Written informed consent was obtained from parents and each child provided assent before involvement. Ethical approval was obtained from the Human Research Ethics Committee of the Federal University of Sao Carlos (89993118.8.000.5504/2018). Permission was also obtained from the head teachers of the schools. The PERF-FIT was administered by a team of trained assessors. The assessors received a six-hour training on test administration, which was facilitated by the lead author. The training consisted of lectures and practical demonstrations. After the training, the assessors practiced instructions and test items in small groups to obtain a solid grasp of the tasks and scoring scheme. The assessors were pediatric physiotherapists, occupational therapist, and a physical educator who had general knowledge of strength and conditioning principles, and typical child development. Each assessor received a test manual for reference. Testing took place in the school premises and children were assessed in pairs. However, in situations where children were too distracted or absent from school, they were tested individually on a separate day. Data collection was completed within a space of three weeks. Structural validity was evaluated by testing the linear increase of the loading used to make the items more difficult (see Additional file 1) and by exploratory factor analysis on the data of the 80 children.
Statistical Analysis
Descriptive statistics such as means, standard deviation, and frequencies were used to summarize the data and experts’ responses. The Content Validity Index (CVI) was used as an estimate of the content validity of each variable in the test battery. CVI is the most widely used quantitative approach for the content validation of instruments. Specifically, Item Content Validity Index (I-CVI) was computed for each test item as the number of experts giving a rating of either 3 (quite relevant) or 4 (highly relevant), divided by the total number of experts in the study. Scale level-Content Validity Index (S-CVI), representing the overall content validity of the PERF-FIT, was computed as the average of the I-CVIs for all the test items. The adopted cut-off for an acceptable level of I-CVI was >0.78 and S-CVI of greater than 0.90 qualifies the test battery for excellent content validity [28].
Further, structural validity of the SIS was checked by examining the hierarchical sequence of the items visually, and by repeated measure ANOVA. In order to test for linearity, maximum scores for the easier items of jumping, hopping and balance were divided by 2 to make the maximum score for all items equal (i.e. 4 points). Structural validity was also examined by exploratory factor analysis. A principal component analysis (PCA) with Varimax rotation with Kaiser-Meyer-Olkin (KMO) test was performed. Eigenvalues greater than one were used to determine the number of dimensions in the PERF-FIT. Data analyses were performed using SPSS (version 24.0, SPSS Inc., Chicago, IL, USA).