A comprehensive functional performance assessment battery development and validation among football players

Background Skill and health-related components are required for the assessment of football players’ functional performance, and there is a lack of literature available to measure football players’ functional performance. The study mostly focuses on developing and validating the tool for football players between the ages of 18 and 25. Methods This study used a research methodology that focused on the development and verification of a scale. The research consisted of two distinct stages, namely tool development and validity testing. Firstly, the expert panel did a comprehensive analysis of the items and domains of the questionnaire. Subsequently, the Delphi approach was used to assess the content validity of the questionnaire. Later on, the evaluation tool was officially named the complete functional performance assessment battery (CFPA) for football players in India. Result The CFPA’s newly developed tool has excellent scale-level content validity, which was more than 0.78 for each item in the tool, i.e., 1 (indicated as extremely relevant), the content validity ratio was bigger than 0.49, and each item’s kappa value was found to be 1, which is excellent. Each item’s universal acceptance was found to be 1 for both the item’s quality and content and Aiken’s V index is also greater than 0.81. Conclusion The CFPA is a valid tool in India that can be used to check the functional performance of football players.


Introduction
Football is the most intricate and popular endurance sport in the world.It is a collective form of poly-structural activities [1].Around the world, 260 million people are enrolled in football clubs, and hundreds of millions more play football without belonging to a national or international football organization [2].The success of football players is determined by their physical makeup, technical proficiency, and tactile performance [3].Motor skills, physiological factors, technological-tactical abilities, psychological development, kin anthropometric features, socioeconomic situation, and a few other outside elements all have an impact on player success [4].
A football game uses a variety of intermittent anaerobic and aerobic energy sources, and players must perform well in areas including primary and motor skills [1].For athletes to perform at a higher level, they need to have high levels of speed, muscular strength, aerobic fitness, explosive jumping power, agility, and other physiological qualities [5].Strength and endurance are the main regulators of football-specific tasks [6].Speed, or the capacity to complete a maneuver in a short amount of time, is another crucial element in football.In football, it is crucial for different body parts to move quickly and over short distances.Speed and strength are vigorously performed by power.Balance is a dynamic, static process that includes several neural connections.For a football game, balance is essential in order to maintain body posture during acceleration and deceleration.The ability of the body to alter bodily parts is known as agility [4].Flexibility is the ability to rotate a single series of joints smoothly and easily through an unrestricted, pain-free range of motion [7].Coordination is defined as insufficiency tackled from the perspective of the particular event and of training [8].The reaction time is the amount of time between the application of a stimulus by the central nervous system and the resulting motor response [9].With the aid of psychological examination, it is easier to comprehend the psychological and mental factors that affect physical and psychological performance in sports [10].For professional football players to develop and improve their physical performance, nutrition and making smart dietary choices are crucial [11].
A comprehensive functional performance evaluation is a set of standardized tests used to gauge players' physical prowess and skill level as well as track their recovery from football-related injuries [12].Evaluation of Functional Performance Batteries offers both qualitative and quantitative sports information.It often evaluates player performance and demonstrates the skill and caliber of football players [6].Also, it has improved the ability to identify a player's functional level, which establishes whether or not they are prepared to resume playing [7].The main purpose of developing the comprehensive functional performance tool is to evaluate the functional performance of Indian football players, which has not been developed in India yet.Functional performance tests are often used to decide whether or not a player can return to sports.According to a systematic review and meta-analysis, functional performance capacity is linked to a return to sports in high-impact sports [13].It is also used for player skill evaluations and advancement so that injuries can be prevented and players can have good performance in sports.It is also useful to assess the physical fitness level to reduce the risk of injury in football players.Creating and validating the comprehensive functional performance assessment battery (CFPA) for Indian football players was the main aim of the study, as there is no such tool developed in India to check functional performance for football players.

Methods
A methodical way to foresee that makes use of panel members' collective opinions is the Delphi technique.A number of medical specialties have come to adopt the Delphi approach, which is an organized way for panel members to reach a consensus [14].The principal aim of the Delphi technique is to produce a trustworthy consensus opinion from a group of experts through an iterative questionnaire process with controlled feedback thrown in.The Delphi process has been applied to a variety of healthcare-related tasks, including assessing existing knowledge and creating assessment tools and indicators [15,16].

Ethical approval
The institutional review board has granted ethical approval for the study protocol.The Indian Council of Medical Research's (ICMR 2017) National Ethical Standards for Biomedical and Health Research Involving Human Participants and the Helsinki Declaration (Revised 2013) were followed during research execution.

Recruitment criteria
A group of 10 experts, including two for the focal discussion and eight for the content validity process, were asked to participate in the study.Participants having master's degrees in sports physiotherapy, with ≥ 5 years of experience, and who are working as academicians were selected for the functional performance evaluation battery of athletes.To qualify as an expert, every subject chosen for the research must meet the enumerated requirements for inclusion.

Study design and setting
This study is about the design and validation of an instrumental investigation.This study was conducted from March 2020 to March 2021 at the department of sports physiotherapy at a reputed university.All experts signed digital informed consent before taking part in the development of the study.The items needed to assess the functional performance of football players were first developed in consultation with two expert panels who have more than 5 years of experience working as sports academicians.The tool was created, and the necessary components were prepared based on comments and suggestions given by the experts.To create the survey, we used the Google Forms platform.Eight experts who completed their post-graduation in sports physiotherapy and had > 5 years of experience working as sports academicians received the questionnaire through Google Forms via email or a WhatsApp link for confirmation.The experts' involvement was entirely voluntary, and they did not get any compensation for it.

Phases of CFPA tool development
The study had two main phases: tool development and validity testing.A detailed description of the phases is described in Fig. 1.

Phase 1: tool development
This phase of the study used to generate items used literature search to develop the tool's items linked to the functional performance assessment skill test, nutritional evaluation, and psychological evaluation, which are related to football, are taken into consideration [6,12,[17][18][19].The following sub-phases comprise the stages:

a. Developing the problem and construct determination
The experts defined the proposed construct and content of the tool.There was no tool to develop to assess the severity, reduce the risk of injury, and improve the functional performance of football players in India.

b. Item generation
There was a sizable pool of goods that would reflect the construction.The tool produced items for the Comprehensive Functional Performance Assessment Battery (CFPA) utilizing literature searches on muscle strength, endurance, speed, power, agility, balance, coordination, response time, psychological health, and nutritional evaluation [6,12,[17][18][19].

c. Extensive literature exploration
Physiotherapy Evidence Databases (Pedro), Scopus, and PubMed/MEDLINE were searched in English using the following keywords: Balance, coordination, response time, psychological health, and nutritional assessment were included in the literature study, as well as muscle strength, endurance, speed, power, and agility.The tool and questionnaire for players were restricted based on age filters.

d. Focal group discussion with the two experts
Based on the results obtained from the literature search, the tool item developed to assess football players' functional skills was first discussed with two experts with a PhD degree in the field of sports physiotherapy and > 5 years of experience.After the initial review by the experts, the tool was developed according to their opinions and suggestions.

e. Categorization of the item in the domain
After the production of items in the comprehensive functional performance assessment battery (CFPA) by using literature exploration and focal discussion, the item was first closely recognized and then categorized in the comprehensive functional Performance assessment battery (CFPA).Items that are categorized for the battery are placed in the Comprehensive Functional Performance Assessment battery (CFPA) of football players.
f. Quantitative evaluation of the content A group of specialists evaluated the item's quantitative evaluation for each of the domains (a sample of 14 items).The level of agreement amongst experts was utilized to assess the content evaluation of items and domains and only one Delphi round was conducted as 80% of experts agreed on an item in the tool, and then it was included for the next round of content validity.

g. Initial draft proposed conversion
After the changes and opinions given by the group of experts for the comprehensive Functional Performance Assessment battery (CFPA), the initial draft was proposed, and then the content validity of the tool was validated by the panel of 8 experts who had completed their post-graduation in the field of sports physiotherapy and held an experience of more than > 5 years in the field of sports physiotherapy.The item's content and quality were both evaluated by a group of eight sports academicians.Using a 4-point ordinal scale, both quality and content were evaluated.The scale runs from 1 to 4, with 1 = not relevant, 2 = somewhat relevant, 3 = quite relevant, and 4 = highly relevant [20,21].According to Lynn's guideline, there had to be 80% agreement between the experts for the item-level content validity index (I-CVI) for eight experts to be 0.83.A minimal I-CVI > 0.78 met Lynn's (1986) criterion as being extremely important [21].Experts chose the item pool based on its quality and content relevance for the extensive Functional Performance Assessment battery.A Google Forms link was sent to the panel of experts via email, a message, or WhatsApp.Five days following the invitation, they received a call, an email, a message, or WhatsApp asking them to take part in the content validation phase.Each expert evaluated the tool's viability before validating it.The content validity round lasted for a total of 2 weeks.

Statistical analysis
SPSS for Windows was used to conduct the statistical analysis (version 25, SPSS Inc., Chicago, IL, USA).To begin with, a four-point ordinal scale was employed to assess the 14 items' content validity.The content validity index (CVI) was calculated by dividing the number of experts that arrived at an acceptable test grade of 3 (quite relevant) or 4 (highly relevant) by the total number of assessments of the test (CVI > 0.78 represents excellent level).Index content validity (I-CVI) = (agreed item)/ (number of experts).Scale-level content validity index (S-CVI/Ave) = (Sum of all I-CVI Scores)/(Number of the item); S-CVI/Ave = (Sum of Portion Relevance)/(Number of the item).Scale-level content validity index based on universal agreement method (S-CVI/UA) = (Sum of UA scores/Number of the item) [17][18][19].
The content validity ratio (CVR) is calculated as ne − N/2/N/2, where ne = the total number of experts divided by the number of experts saying the item is essential, and N = the total number of experts in the panel.Kappa value (k) = (CVI − Pc)/(1 − Pc).Where Pc is the probability of a chance occurrence (k = 0.75 indicates an excellent value).Aiken V was calculated as V = s/ [n (c − 1)]; s = r − lo; lo = lowest value.c = highest value r = numbers given by the rater [17][18][19].

Results
A group of eight physiotherapists with backgrounds in sports evaluated the Functional Performance Assessment Battery (CFPA).In first the round, each of the functional performance assessment tests received 100% of the response rate.
The development of a Functional Performance Assessment Battery (CFPA) for Indian football players was the main objective.The steps involved in developing the tool were as follows: choosing the item, formulating the problem, choosing the construct, creating the item, conducting a literature review, categorizing the item in the domain, evaluating the content's quality, creating an initial draft, and producing the final document.In response to feedback from experts in the Delphi rounds, the instrument was modified for the content validity round.The details of the Performa are presented in Supplementary files 1 and 2.
The content validity ratio for the CFPA was greater than 0.89, and the scale level of content validity for each tool item-including item 1 (described as highly relevant)-was greater than 0.78 (Table 1).The item's quality and content were both universally accepted at 1 (Table 1).Each item's content validity at the item level was 1 (Table 2).The kappa value for each item was found to be 1, which is excellent (Table 3).Aiken's V index was greater than 0.81, which indicated that the examiners strongly agreed with each other's opinions (Tables 4 and 5).
Table 1 Relevance rating on 14 items in tool by eight experts for the content of the item and quality of the item Relevance rating for content of the item Experts' agreement I-CVI UA Average portion of item judged as relevance across the 8 experts = 1 S-CVI/Ave-Sum of all i-CVI scores/No. of item = 14/14 = 1 S-CVI/Ave-Sum of proportion relevance rating/Number of expert = 8/8 = 1 S-CVI/UA-Average score of UA Scores across all the item / No of item = 14/14 = 1 Relevance rating for quality of the item Experts' agreement I-CVI UA

Discussion
A comprehensive functional performance assessment battery was created and validated to help football players evaluate their physical fitness, functional performance, and risk of injury during gameplay.It is necessary to assess the injury risk and effectively manage the recovery of injured players [22].The validation of the tool necessitates the expertise of professionals.Various factors, including the quality of the inclusion criteria, the number of experts needed, guidelines for preparing evaluation templates, methods for collecting quantitative and qualitative data, and appropriate statistical analysis, should all be carefully considered.
A group of panels of experts validated the tool, and the tests that received ≥ 80% of the response rate were selected for the content validity round.Between the experts, the strength of the consequences reached in the study is reflected in the remarkably high level of agreement.Each item's content validity (I-CVI) in the battery for the functional performance assessment test for both content and quality of the item was greater than the accepted value (0.78).It indicated that each item included in the tool was highly relevant.The S-CVI UA (universal acceptance) for the content of the item was 1 and the quality of the item was 0.92.The tool S-CVI/UA value was within the acceptable range, which was more than (≥ 0.8), suggesting the relevant content the tool can measure.The S-CVI/Ave for the Functional Performance Assessment battery for content was 1 and the quality of the item was 0.99, which was more than the accepted value (≥ 0.9).The kappa coefficient (k*) for each item in the functional performance assessment tool is 1, and the psychological evaluation of the item's quality was 0.69, which is excellent and good (values for kappa, as proposed by Cicchetti and Sparrow: fair = k* of 0.40 to 0.59, good = k* of 0.60 to 0.74, and excellent = k* of 0.75 to 1.00).The content validity ratio (CVR) for each item in the comprehensive functional performance assessment test in the tool for content and quality of the item is 1, and the psychological evaluation of the quality of the item is 0.75 which was accepted as a higher degree of relevancy of 0.49.The Aiken's V index for each item in the tool for comprehensive functional performance assessment tool for both content and quality of the item was between V 0.81 and 1.00, which was strongly agreed and relevant [23][24][25][26].The tests selected by the group of experts that had high content validity were demographic details, body composition, general examination, single hop test, Yo-Yo intermittent test, shuttle run test, T-test, vertical jump test, stork stand balance test, sit and reach test, alternate handball toss test, visual and acoustic reaction time, Sports anxiety Trait Inventory and 3-day dietary protocol.
The purpose of the subjective examination including demographic details was to ensure that the player is medically safe for their choice of sporting activity; it is an important component of the assessment in football [27].Body composition evaluation tracks the changes in the various morphological components to customize training positions and roles within the team and to provide a unique relationship between health and sports performances [28].General systemic examination maximizes safer participation in sports as it may detect medical conditions that predispose the player to injury and illness hence it is a valid component for assessing the player in football before the game.In reference to other evaluation tests of tools that closely replicate the pattern of movement in football, they were thus found useful and valid in measuring the football players' performance as well as physical fitness.In relation to psychological evaluation state-trait anxiety inventory was used to check issues related to anxiety, depression, self-esteem issues, fear of failure during the games, and stress-related concerns in players for the game [29].Finally, in relation to nutritional evaluation a 3-day dietary recall was done for the players to determine how much quantity and type of food they required at specific intervals of the day.The recall was done using the 24-h recall method for three consecutive days.It was done to check the physical demands needed for the body during the training status of the players and to enhance their performance in the game [30].
CFPA had an overall highly relevant and excellent item content validity index, Scale-content validity index for both content and quality of item, universal acceptance, and content validity ratio.Kappa value and Aiken's V coefficient were also excellent for each functional performance test present in the tool for the quality and content of the item.A CFPA battery can be used to assess the risk of injury and the physical fitness level of football players.It can also be a helpful tool for managing the wounded player's recuperation and predicting the player's performance in the future.The current study will help sports physiotherapists assess the tailored training regimen and track recovery from sports-related injuries as well as football-specific talents.
The full functional performance assessment battery, one of the study's shortcomings, encompasses items and components, making the assessment potentially challenging.It ought to concentrate on just one thing at a time.Sports physiotherapists must go through training before utilizing the CFPA, which will improve player Table 3 The item-content validity index (I-CVI), Probability of Chance Agreement (Pc), and the Kappa designating agreement of relevance (k*)

Conclusion
The Complete Functional Performance Assessment battery is a valid instrument that may be utilized with football players, according to the results of the current study.The instrument may be utilized in a football-specific setting on the field and will aid in maintaining the player's physical condition as well as enhancing individual and team performance.CFPA is the first measurement tool used in India among football players.

Fig. 1
Fig. 1 Study phases of CFPA development and validation a. Content validation by the Delphi method I.The Sample size for the content validity round: eight experts for content validity in the Delphi round II.Content validation of the instrument was carried out by a panel of experts Abbreviations: I-CVI = Item-Content Validity index, UA = universal agreement, S-CVI = Scale Content Validity index, Relevance rating recorded as 1 = (relevance scales 3 and 4, relevance rating recorded as 0 = (relevance scales 1 and 2)

Table 2
Item generated domains and percentage level of agreement between the experts of item-level content validation for the content of the item and quality of the item

Table 4
CVR for items of each dimension where Ne represents the number of experts who rate an item as "essential" Abbreviations: CVR content validity ratio,N = total no of panelists, Ne = no. of panel lists Indicating item essential use of the instrument and their ability to recognize play behavior.Future recommendations call for the creation of standardized protocols so that each appropriate performance test can be selected as a tool and have individual test scores created.