| Summary: | During the growth spurt (GS) which forms part of the mid-adolescence period of boys (13-17
years), considerable changes take place in the body composition of boys. It is therefore an
unstable period where imbalances in body proportions (muscle mass, fat mass, neurological
development) occur, that might have an effect on sport performance. It is also accompanied
by changes in physical and motor fitness. The study firstly aimed to determine
anthropometric growth changes in stature, arm span, mass, sitting height and sitting height
ratio during mid-adolescence over a period of three years. The study secondly aimed to
investigate the developmental changes in physical fitness (muscle strength, aerobic
endurance) and motor fitness abilities (speed, agility, hand- eye coordination, explosive
power) during the mid-adolescence phase of boys and finally to investigate possible
relationships between anthropometric and physical and motor fitness abilities over the course
of three years.
A convenience sample consisting of all the grade 8 learners (n=182) of a quintile 5 high
school in Potchefstroom in the North-West province of South Africa was selected to
participate in a longitudinal growth research project over a three year period. Only the boys,
with a mean age of 13.58 years in grade 8, of whom 95.4 % were white, 2.3% black and 2.3%
colored boys, were part of the study. In 2010, 87 boys had complete measurements, while the
final group in 2012 with completed follow-up measurements, were 73 boys.
The physical and motor fitness components were measured according to the Australian Sport
Search Program consisting of 10 tests (4 anthropometrical tests, 5 motor fitness tests, 1
physical fitness test). The cricket ball throwing test was added as an additional test. The
anthropometrical measurements were made using the protocol of ISAK, while sitting height was measured according to the Canadian Sports for Life protocol. Sitting height ratio was
calculated according to the formula (sitting height/stature x 100).
The data was processed by “Statistica for Windows” Statsoft-computer program package.
Descriptive statistics that included means (M), standard deviations (SD) and minimum and
maximum values were used. A repeated measures over time analysis of variance (ANOVA)
with a Bonferonni adjustment was done to analyze the differences over a period of 3 years
within the group for all variables, where p<0.05 indicates a statistically significant difference.
A partial correlation analysis was used to determine correlations between variables. Practical
significance of correlations was determined according to Cohen’s d-value (0.1=small,
0.3=medium, 0.5=large).
The results showed that during mid-adolescence in the period 13.58-14.58 years, boys grow
considerably in stature, body mass, arm span and sitting height with accompanying
improvement in motor and physical fitness abilities while sitting height ratio showed the
greatest increase from 14.58-15.57 years. Stature, mass and arm span showed a parallel
development up to 15 years after which further development leveled off, while mass increase
showed no leveling off. Speed, agility, coordination and isometric-dynamic shoulder strength
(basketball throw) also showed the biggest and significant improvement from 13.58-15.57
years, while explosive leg power and upper body arm and shoulder strength (vertical jump,
cricket ball throw) showed the biggest and significant improvements during the period from
14.58 to 15.57 years. Significant correlations up to r=0.74; p<0.05, were found between
changes in physical and motor fitness abilities and anthropometric variables, although the
correlations become smaller over the 3-year period. Hand-eye coordination showed no
correlation with any anthropometrical changes, while upper body strength correlated with all
the anthropometrical measurements except sitting height ratio throughout the three years.
It was concluded that the most accelerated growth and development took place from 13.58-
15.57 years in boys when they are in their first high school year and which falls within the
mid-adolescent period (13-15 years). Furthermore, clear relationships were found between
anthropometric, motor- and physical fitness variables. This knowledge of the rate of growth
and motor fitness development and the relationships between these variables during the midadolescence
period can provide a better understanding of changes that boys underwent during
the mid-adolescent period, and can help monitoring the level of physical maturity in
adolescents in order to develop training, competition and rehabilitation programs according to their developmental and not their chronological age. This cannot only prevent injuries, but
also prevent early burnout in sport. === MA (Sport Science), North-West University, Potchefstroom Campus, 2014
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