1

The effect of ball features on health risks in competitive children and youth football conducted by the Friedrich-Alexander University

Erlangen-Nuremberg (Condensed Version)

1. Introduction ....................................................................................................................... 2

2. Methods ............................................................................................................................ 4

3. Results ............................................................................................................................... 7

4. Conclusion ....................................................................................................................... 11

Table of Figures ................................................................................................................... 12

References ........................................................................................................................... 13

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1. Introduction

There has been an ongoing discussion about the risks of heading in football over the past

decades focusing on the risk of concussion during games, negative long-term effects of

consecutive heading and the protection of the head. However, most of these studies

investigated an adult population but not the possible risks for children. Furthermore, these

studies focused on concussions while other health risks due to the ball itself were often

excluded from the scope. To give a sound statement on the influence of ball features on

various factors of children’s health in football, a systematic analysis and review of the current

state of research based on internationally accepted standards is needed.

Here, various features of the ball need to be taken into account in order to show the whole

picture. These features are the size of the ball, the weight of the ball, ball pressure, the ball’s

texture and its rate of absorbing water in wet weather conditions (cf. Figure 1).

Looking at how physiology and technique in football are developed, these two have a clear

pathway of how to be taught. Subcategories such as the size of the pitch, the size of the

goal, the number of goals, the number of players, substitution systems, the duration of the

game, the system of rules and the form of organization (cf. Figure 2) impact the

periodization. Hence, they are being used at a certain age or at a certain level of skill. The

same holds true for parameters of the ball, as mentioned above. Children should play with a

ball that is appropriate for their age and skill level (Wein, 2016).

Figure 1: Properties of the ball (Lochmann, 2017)

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Horst Wein (2016) named 25 reasons why children should use age appropriate balls for their

football development (cf. Figure 3), which can be further divided into three categories such

as tactical development, technical development and health development.

Figure 2: Features to design competitions age appropriately (Lochmann, 2016)

Figure 3: The main hypothetical advantages of age appropriate parameters of the ball (Lochmann, 2016)

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2. Methods

The systematic review of the existing literature followed the guidelines of the Cochrane

handbook for systematic reviews (Higgins, 2016). Here, a three phase process consisting of

generating the keyword list for the literature research, screening the identified literature

based on predefined criteria and the qualitative analysis of the remaining literature was

conducted.

Figure 4 shows the analysis scheme of the systematic literature review according to the Flow

Diagram of Moher et al. (2009), conducted by the scientists at the Department for Sport and

Sport Science at the Friedrich-Alexander University Erlangen-Nuremberg in Germany. In the

process of identifying relevant papers, 203 records were found, 34 of which ultimately were

classified eligible for full-text analysis (cf. Figure 6).

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Figure 4: Analysis Scheme of the systematic literature review conducted by the Department of Sport and Sport

Science at the FAU

Going into greater detail, Figure 5 shows the list of key words which were chosen to search

for valid records in databases such as Pubmed, Scopus and google scholar, representing

categories such as language, health threats, ball features, long-term effects on bio-medical

health and demographic.

From: Moher D, Liberati A, Tetzlaff J, Altman DG, The PRISMA Group (2009). Preferred Reporting Items for Systematic Reviews and Meta-Analyses: The PRISMA Statement. PLoS Med 6(6): e1000097. doi:10.1371/journal.pmed1000097

Formoreinformation,visitwww.prisma-statement.org.

AnalysisSchemebasedon

PRISMA2009FlowDiagram

Databases:Pubmed|Scopus|googleScholar

Recordsidentifiedthroughdatabasesearching

(n=229)

Screen

ing

Inclu

ded

Eligibility

Iden

tifica

tion Additionalrecordsidentified

throughothersources(n=0)

Recordsafterduplicatesremoved(n=203)

Recordsselected/screened(n=203)

Recordsexcluded(n=169),withreasons:noreferencetotheballoritsfeatures,noreferencetochildrenorwomen,noreferencetophysiology,notransfertopotentialinjury/threatforhealth;

Full-textarticlesexcluded(n=2),withreasons:poor

quality,problemsretrievingfulltext

Studiesincludedinqualitativesynthesis

(n=32)

Studiesincludedinquantitativesynthesis

(meta-analysis)(n=0)

Full-textarticlesassessedforeligibility(n=34)

Notmeaningfulduetoaninsufficientsetof

calculabledata

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After the records were screened, 34 records fulfilled the criteria for eligibility and were taken

into full-text analysis.

Here, criteria from van Tulder (2003) were applied in order to give a qualitative analysis of

the 34 records, 2 of which had to be excluded due to poor quality and difficulty to retrieve.

Figure 6 shows the qualitative criteria that all 32 records were analyzed by.

Figure 5: Key Word List

Figure 6: Criteria for quantitative analysis

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3. Results

All in all, the epidemiological data, i.e. the studies that report on past events such as

recorded and cataloged data are not useable to address the question what effect ball

features have on the health risk in competitive children and youth football. Hence, only three

studies with theoretical data and some minor experimental trials within them are shown in the

following section. Figure 7 shows all results after the qualitative criteria were applied.

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Figure 7: Qualitative Analysis according to van Tulder (2003) of 32 retrieved Studies

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Shewchenko et al. (2005) use a numerical model in combination with laboratory data to

describe the increase of linear head acceleration when the player’s head comes into contact

with the ball, when ball mas increases through the absorption of water (cf. Figure 8) or

through increased ball pressure (cf. Figure 9).

Figure 8: Numerical Model from Shewchenko et al. (2005), p.i35

Figure 9: Numerical Model from Shewchenko et al. (2005), p.i35

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Queen et al. (2003) use another theoretical calculation in order to describe how linear head

acceleration increases using a size 3 ball at 12 psi inflation at various speeds. Three

different head masses are illustrated in Figure 10. The lower the head mass of the player, the

higher its linear acceleration while maintaining constant size and inflation of the ball.

Babbs (2017) uses another theoretical calculation to show sampling distributions for head

acceleration. Ultimately, accelerations of the head, are experienced to be greater by children

than those experienced by adults. The soccer ball which is currently used in youth soccer,

does not make up for the difference in size, weight and pressure of young players. “However,

a modified size 4 ball can make heading as safe for children as it is for adults” (Babbs, 2017)

Figure 11 shows three different types of balls and the respective mean head acceleration

they cause.

Figure 10: head acceleration at different head masses from Queen et al. (2003), p.2072

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4. Conclusion

To conclude, it can be stated that parameters such as the weight, size and inflation of the

ball as well as its capability to absorb water do have an effect on the health risks in children

and youth football. However, due to the lack of conclusive epidemiological studies, the

conclusions made are based on theoretical calculations only and therefore experimental

studies with a high methodological quality are highly recommended. These studies would

then allow a detailed insight into the true epidemiological effects of individual parameters on

children and youth players and would allow further efforts to be made to reduce these injury

risks.

Figure 11: Head velocity change from Babbs (2017), p.9

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Table of Figures

Figure 1: Properties of the ball (Lochmann, 2017) .................................................................. 2

Figure 2: Features to design competitions age appropriately (Lochmann, 2016) .................... 3

Figure 3: The main hypothetical advantages of age appropriate parameters of the ball

(Lochmann, 2016) ........................................................................................................... 3

Figure 4: Analysis Scheme of the systematic literature review conducted by the Department

of Sport and Sport Science at the FAU ............................................................................ 5 Figure 5: Key Word List .......................................................................................................... 6

Figure 6: Criteria for quantitative analysis ............................................................................... 6

Figure 7: Qualitative Analysis according to van Tulder (2003) of 32 retrieved Studies ............ 8 Figure 8: Numerical Model from Shewchenko et al. (2005), p.i35 ........................................... 9

Figure 9: Numerical Model from Shewchenko et al. (2005), p.i35 ........................................... 9

Figure 10: head acceleration at different head masses from Queen et al. (2003), p.2072 .... 10 Figure 11: Head velocity change from Babbs (2017), p.9 ..................................................... 11

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