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 feasibility and validity 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 6-12 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 subscale.
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 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 the core skill-related physical fitness domains that were thought to be important for children’s development and growth. Based on our search, six key skill-related physical fitness domains were identified including agility, power, balance, coordination, speed and reaction time and examples of items adequate per domain were described (Table 1).
Table 1. Definitions used for the domains of skill-related physical fitness (adapted from Caspersen, Powell &Christenson, 1985).
Domain
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Theoretical definitions
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Operational definitions
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Agility
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The ability to rapidly change the position of the entire body in space, with speed and accuracy.
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The child is asked to jump side to side at high speed and with great efficiency.
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Balance
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The maintenance of equilibrium while stationary or in motion.
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The child is asked to stand on one leg while holding on to his free foot for an extended period of time (static).
The child is asked to grasp his/her unsupported foot while making slow steps in the agility ladder (dynamic)
The child is asked to move his arms and trunk forward to pick up an empty can while standing on one leg.
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Coordination
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The ability to use the senses, such as sight and hearing, together with moving body parts, in performing motor tasks smoothly and accurately.
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The child is asked to time arm and leg movements to perform a catch or make consecutive jumps smoothly.
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Power
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The rate at which a person can perform work (strength over time).
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The child is asked to apply great force to a heavy object to make a throw or propel the whole body forwards to make a long jump.
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Speed
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The ability to perform a movement within a short period of time.
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Running speed is tested in the agility ladder where the child is moving forward from the start line quickly to the end of the ladder, turn and run back.
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Reaction time
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The time elapsed between a stimulus and the beginning of the reaction to it.
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Most items have a start signal to which the child has to respond; many adaptation made to make a movement successful are based on rapidly responding to a stimulus and adapt the movement to that stimulus to avoid stepping on a bar (agility items) or estimate the trajectory of a bouncing or thrown ball.
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These domains were selected because of their cross-cultural applicability, relevance to childhood routines and games, ease of testing in schools in low-income settings and their ability to enhance performance 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 [14] and to create more awareness that evaluation of skills-performance related physical fitness has important implications for child development, physical education and policy decisions [15].
Item identification.
Based on the literature search and pre-defined criteria (see Table 2), twenty items representing the six core domains 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 (i.e. motor performance and agility and power components) as described earlier. The theoretical and operational definitions of each domain were clarified to guide task identification. 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).
Table 2. Criteria for selecting items of the PERF-FIT test battery.
Criteria
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Description
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A
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Tasks should be able to measure skill-related physical fitness.
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B
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Tasks should allow for progressive increase in difficulty (i.e. task loading).
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C
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Tasks should have cross-cultural applicability and be appropriate for children aged 6-12 years
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D
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There should be no specific space restrictions for testing
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E
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Materials needed for the test should be low-cost. (See Additional file 3)
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Pilot testing.
The last phase of the development of the PERF-FIT was the pilot-testing phase. The final items were tested in two small samples of South African children (n=10 and n=20) to assess feasibility, acceptability, ease of administration and implementation challenges. Feedback that was obtained from the children and test administrators in the pilot samples were used to refine aspects of the test items, details in the instructions and the scoring forms 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
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.
Content validity
Seven experts (all experienced clinicians with doctorate degrees; three from Africa, two from South America, and two from Europe) assessed the relevance of the PERF-FIT items. 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 (typically developing children and children with poor motor coordination, e.g. Developmental Coordination Disorder (DCD), Attentional Difficulty 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 [16] (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 [17].
Structural validity
The PERF-FIT test was validated in 80 Brazilian children aged 7-12 years (mean 9.2 SD 1.1). 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 (i.e. physical therapists and a physical education teacher). 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 [17].
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 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).