Investigation of growth, development, and factors associated with injury in elite schoolboy footballers: prospective study
BMJ 2009; 338 doi: https://doi.org/10.1136/bmj.b490 (Published 27 February 2009) Cite this as: BMJ 2009;338:b490
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We would like to thank all authors who have responded to our recent
article.
It is reassuring to know that the frustrations of trying to be more
scientific about training and and injury prevention in youth football
players is shared by other groups. The issue about the inconsistency of
maturity status has obviously raised questions that are, as yet unresolved
but never the less future clarification of the situatiion is better than
accepting poorly justified assumptions about training intensity and
growth.
The BMJ article reflects a fraction of the research that we are
currently undertaking to establish a more scientifically rigorous approach
to training elite youth players. the concept of "windows of opportunity"
is particularly challenging in that it has become customer practise
without a credible evidense base. Our ongoing research will hope to
establish the efficacy (or not) of "windows of opportunity" which play a
significant role in long term athletic development plans supported by UK
Sport.
The statistical result that was perceived as "odd" was simply that
one analysis, which was comparative (ANCOVA), used training and playing
time as covariates, whereas the other analysis (Regression),which was done
to determine predictors of injury, used the same two variables as
determinants.
The BMJ rapid responses were right to highlight the lack of evidence
and the potential issues associated with defining skeletal maturity in the
context of training intensity. The ethical dilemma of using x-rays as a
means of ascertaining the skeletal age in youth elite footballers was
seriously considered by all involved in the study but with the advent of
new machinery that minimise the risk of exposure it was felt that the
benefits far outweighed the risks. Inappropriate training intensity in
elite youth football players as well as being non-scientific, could result
in burn-out, injury and even the loss of career prospects.
To be successful in elite sport it has been shown that individuals
have to be involved at an early age and it is important that practitioners
ensure that a balance is struck between an optimum enviroment and safety
for these developing players.Elite sport exists whether we approve or not
and it would be wrong, in terms of the individual and society, not to
optimise excellence wherever it is found.
Competing interests:
Authors of the article.
Competing interests: No competing interests
The paper by Johnson et al.1 provides a valuable contribution towards
understanding the role of biological age and maturation in relation to
occurrences of injuries among elite nine to sixteen-year-old English
football players.
However, some issues deserve further emphasis and deeper discussion.
As these authors explain, pressure to produce new players frequently
exists, involving financial interests. In this respect, the performance
demands placed on child and juvenile players even before completely
maturing, with high training loads, have been unreasonable. This can be
exemplified with the international under-17 (World Cup) and under-15
(continental) tournaments, sponsored by FIFA or continental
confederations.
On the other hand, despite these demands, it has not been proven that
high yield in youth team divisions is associated with high performance in
professional football. On the contrary, studies by our group (not yet
published) have demonstrated the opposite. For example, we have found that
the great majority of players who were finalists in world under-17
tournaments did not even compete in the World Cup, the most important
competition in football.
The reasons why such successes are not repeated over the years may
lie firstly in the interest in using young men of greater maturity, with
greater strength and endurance and therefore greater chances of reaching
victory, as already studied by other authors2,3. A second explanation may
be connected with the large number of injuries sustained over the course
of the early demands imposed on young sports players, which are often
similar to the burdens placed on adults.
Thus, I congratulate Johnson et al. for their paper and stress the
importance of conducting further investigations, which should involve
issues relating to maturation.
References
1. Johnson A, Doherty PJ, Freemont A. Investigation of growth,
development, and factors associated with injury in elite schoolboy
footballers: prospective study. BMJ 2009; 338: b490.
2. Helsen WF, Winckel JV, Williams M. The relative age effect in
youth soccer across Europe. J Sports Sci 2005; 23(6): 629-36.
3. Carling C, le Gall F, Reilly T, Williams AM. Do anthropometric and
fitness characteristics vary according to birth date distribution in elite
youth academy soccer players? Scand J Med Sci Sports 2009; 19(1): 3-9.
Competing interests:
None declared
Competing interests: No competing interests
We find it surprising and perhaps a little distasteful that a modern
medical journal should - even by inference - support the concept of
elitism in this emotionally vulnerable age group. Concern for child safety
has moved us to write this letter. Assessing skeletal maturity by studying
radiology is of course an old technique. However, since the hazards of
exposure to Roentgen rays became known scores of years ago, this method
has seldom been favoured, except for sound clinical purposes.
We suggest that the "benefits" to young trainee footballers
undergoing six (clinically unnecessary) X-ray examinations may be out-
weighed by the potential for harm due to exposure to radiation. The
authors note that caution is needed in interpreting differences in injury
occurrence due to the complexity of the contributing factors. Skeletal
maturity may, in fact, not be of very great significance in any event.
Dr JK Anand Dr JW Myles
3 Wayford Close 17 Audley Gate
Peterborough Peterborough
PE3 9NL PE3 9PG
Competing interests:
None declared
Competing interests: No competing interests
It makes for a colourful front cover and a striking headline (YOUNG
FOOTBALLERS The risks of intensive training), but what does the paper by
Johnson et al (BMJ 2009;338:b490) actually mean?
The Abstract says that "Maturity, defined by the difference between
chronological age and skeletal age, plus training and playing hours
together
predict injury in schoolboy footballers." It then says that "The use of
skeletal
age measurements to establish accurate 'windows of opportunity' for
training
is more appropriate than the commonly used chronological age."
So what is the evidence for this latter statement? The answer is –
not a lot.
From the Results, injury incidents were unrelated to maturity status
after
adjusting for playing time, training time, height and position played (P =
0.7).
Conversely mean injury occurrence was strongly associated with maturity,
adjusted for match play time and training time (t = -2.65, P < 0.05).
This is
odd – what is the distinction between ‘injury incidents’ and ‘mean injury
occurrence’, and why are their findings contradictory? Also, what has this
to
do with ‘windows of opportunity’?
The paper is remarkable for its lack of statistics. Apart from a
smattering of F,
t and p values there are virtually no statistical results. Though some may
view
this as a bonus it does question the validity of the analysis. The
research
question posed – how does injury risk relate to maturity status – is
complex.
It depends on age and height as well as maturity, all of which change over
time. The study covered six seasons, with players appearing in
multiple seasons, yet age trends and repeated measures are ignored in the
analysis. So not only is the analysis poorly described, it is simplistic.
Overall, the paper’s claim that maturity affects injury risk is
singularly
unconvincing.
Competing interests:
As a BMJ statistics editor I
reviewed this paper twice.
Competing interests: No competing interests
Dear authors,
I would like to congratulate you on the quality of your study and for
braving the often "hostile" medical world when employing x ray films to
determine bone age. In previous work on biological maturity and injury in
elite football players1 our work also employed the use of an x ray film
during pre season screening and met with tough "ethical" criticism on
behalf of reviewers and readers. The question I ask is do the negatives ie
one off slight exposure to radiation outweight the benefits ie
classification into maturity groups? Once players are clinically
considered to be early, normal or late maturers then training loads can be
adjusted accordingly (or training groups adjusted according to maturity
status) and practitionners can take into account individual player
maturity status when evaluating performance during testing and match play.
Other work on elite youth football has also shown that younger players
ahead in biological maturity2 do not always achieve success later on which
may again strengthen the case for early, systematic measurement of
maturity status.
Yours,
Christopher Carling
1 Le Gall F, Carling C, Reilly T. Skeletal age and injury in elite
youth football. Scand J Med Sci Sports 2006;17:564-72.
2 le Gall F, Carling C, Williams M, Reilly T. Anthropometric and
fitness characteristics of international, professional and amateur male
graduate soccer players from an elite youth academy. J Sci Med Sport. 2008
Oct 1. [Epub ahead of print]
Competing interests:
None declared
Competing interests: No competing interests
Do talented young football players become elite adults?
Dear authors,
I would like to congratulate you for the quality of your study. It is
indeed very important, for both scientists and coaches, to share data on
the effect of maturity on performance and other sports related variables.
It is also very important to have such data available in the literature
from elite academies, as yours.
I agree that evaluation of skeletal age should be part of assessment
in high level football clubs. This is for two reasons: a) to evaluate
physical fitness tests bearing in mind the biological age of the player,
and b) to create training groups according to the biological and not
chronological age.
My major concern at this point relates to the possible negative
effect of excess, pre-mature stress on these young football players. Is it
possible that psychological overload due to more demanding training and
games for early maturers be detrimental to their sports development?
One final point. Since authors have longitudinal information for
these football players it would be very interesting to see data on the
“windows of opportunity” and how this is influenced by the biological age.
Sincerely,
George Nassis, MSc, PhD
Department of Sports Medicine and Biology of Exercise, Faculty of
Physical Education and Sports Science, University of Athens, Greece
Exercise Physiologist-Sports Scientist
Head of Panathinaikos Performance Lab,
PANATHINAIKOS Football Club, Greece
Competing interests:
None declared
Competing interests: No competing interests