choose to participate or drop out from a sport, selection decisions in most sports are
ordinarily made by adults without input from the youth athletes (Malina 2009 ).
Studies addressing potential influences of individual differences in biological
maturation on physical activity and sport talent development programs increasingly
use two noninvasive maturity indicators:
- Percentage of predicted adult stature at the time of study (Roche et al. 1983 )is
based on the assumption that among youth of the same chronological age, the
one closer to his/her predicted adult height is more mature than another who is
further from adult height. It is an indicator of maturity status. The method had
moderate concordance with maturity status classifications based on skeletal age
in several samples of youth athletes. - Maturity offset (time before or after peak height velocity) is predicted from
sex-specific equations based on chronological age, weight, height, sitting height,
and estimated leg length; age at peak height is predicted as the difference
between maturity offset and chronological age (Mirwald et al. 2002 ). It is thus
an indicator of maturity timing. In two independent longitudinal series, pre-
dicted ages at peak height velocity increased with chronological age at pre-
diction, had reduced ranges of variation, and were affected by actual ages at
peak height velocity in both sexes and age at menarche in girls (Malina and
Kozieł2014a,b; Malina et al. 2016 ). The original prediction equations have
since been modified and calibrated with external samples; the new equations
include age and sitting height in boys and age and height in girls (Moore et al.
2015 ). The new equations have not yet been validated in an independent lon-
gitudinal sample.
More detailed evaluation of the protocols is beyond the scope of this chapter (see
Malina2014b; Malina et al. 2005 , 2007 , 2012 ). The protocols were developed on
healthy children of European ancestry. They need further validation in independent
samples and in different ethnic groups.
Movement Proficiency and Physical Activity
It is not surprising that children who are more proficient in movement skills tend to
be more physically active, although interest in relationships between motor profi-
ciency and physical activity is relatively recent (Stodden et al. 2008 ). The need to
demonstrate and experience competence is, after all, a fundamental component of
intrinsic motivation (Ryan and Deci 2000 ). Studies of movement proficiency in
young children need to be viewed in the context of neuromuscular maturation and
motor development per se. Basic movement patterns as in running, jumping,
skipping, throwing, and the like are developing at these ages, and there is con-
siderable inter-individual variation (Seefeldt and Haubenstricker 1982 ; Malina et al.
2004 ).
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