The measurement of cardiorespiratory fitness has been extensively researched among adult
populations, but very few researchers have focused their attention on the cardiorespiratory
fitness of children and adolescents. Due to various constraints of direct 2max
VO testing, various
indirect testing methods have been developed of which the 20-m Shuttle Run Test is the most
widely used testing method. The influence of various anthropometric, physical and motor
performance components as well as certain demographic factors such as gender, race, living
area, and sport participation as well as physical activity level on the 2max
VO value of
participants seems to suggest that 2max
VO can be predicted by including these components in
prediction models. It is against this background that the objectives of this study are provided.
The following four objectives of the study were achieved through a literature review: Firstly, to
name and describe the various direct and indirect methods for determining 2max
VO ; secondly,
to provide a review on the findings with regard to the aerobic performances or 2max
VO values of
children and adolescents; thirdly, to discuss the possible influence of various anthropometric,
physical and motor-performance components on the aerobic performances or 2max
VO values
of the last-mentioned groups of subjects. As part of this objective, other literature-identified
factors such as certain demographic factors (living area, race and gender), sport and physical
activity participation level which may also influence the aerobic performances or 2max
VO values
of the participants, were also discussed; fourthly, all literature identified models for the
prediction of aerobic performances or 2max
VO values in children, and in adolescents were
mentioned and discussed. The next few objectives were achieved through a selected group,
cross-sectional experimental research design; fifthly, to develop a valid 2max
VO prediction
function from several anthropometric measurements and demographic factors such as gender, race and living area as well as sport participation level of a cohort of adolescents living in the
Tlokwe Local Municipality (Potchefstroom area) of North West Province, South Africa; sixthly, to
develop a 2max
VO prediction function from the physical and motor-performance components as
well as demographic variables such as gender, race and living area as well as sport
participation level of a cohort of adolescents living in the Tlokwe Local Municipality
(Potchefstroom area) of North West Province, South Africa; and finally, to determine the validity
of the 20-m SRT to estimate the 2
VO and 2max
VO of a cohort of adolescent boys in the
Tlokwe Local Municipality (Potchefstroom area) of North West Province, South Africa.
In order to fulfil the fifth and sixth objectives of the study, a total of 214 grade 8 adolescents
(boys: 88 and girls: 126) (age: 15.82 ± 0.68 years) of high schools in the Tlokwe Local
Municipality (Potchefstroom area) of the Dr Kenneth Kaunda District of the North West
Province, South Africa were purposefully selected from pre-acquired class lists, from six
secondary schools. Data was collected by means of various questionnaires, anthropometric
measurements and physical and motor-performance tests, which also included the 20-metre
SRT. For the fulfilment of the final objective of the study, 52 boys were purposefully selected
from the above-mentioned group that completed various questionnaires as well as the 20-m
SRT while they were fitted with a portable gas analyser apparatus.
With regard to the anthropometric and demographic variable prediction model, the forward
stepwise regression analysis results showed that muscle mass percentage, sport participation
level, stature, hip circumference and ectomorphy act as significant predictors (p ≤ 0.05) of the
indirect, 20-m SRT 2max
VO values of a cohort of adolescents. Muscle mass percentage
emerged as the strongest predictor (59%) of adolescents’ 2max
VO values, followed by sport
participation level (6%), ectomorphy (2%), stature (1%) and hip circumference (1%). The
physical, motor-performance and demographic prediction model revealed that 10-metre speed,
sit-up repetitions, sport participation level, handgrip strength, Vertical Jump Test (VJT) Tendo
peak power, maximal heart rate (HRmax), living area, right shoulder external rotation flexibility
(RPSERT), horizontal jump test distance (HJT) and right Modified Thomas iliopsoas flexibility
(RMTIT) served as significant predictors (p ≤ 0.05) of the indirect, 20m-SRT-derived 2max
VO
values of a cohort of adolescents. However, only 10-metre speed served as a major contributor
(53.5%) to the indirect 2max
VO values of the adolescents. The rest of the variables contributed
17.4% to the overall variance in 2maxVO values. Overall, the last-mentioned anthropometric, physical, motor performance and demographic variables were responsible for 70.5% of the
variance in the 2max
VO values of the adolescents. Cross-validations also revealed that both
models are valid for predicting the 20-m SRT-derived indirect 2max
VO values of this cohort of
adolescents.
The 20-m SRT validity study showed that a significant difference (p ≤ 0.05) existed between the
predicted indirect 2max
VO results (42.06 ± 4.53 ml/kg/min) as obtained from the 20-m SRT
booklet and the direct 2max
VO results (50.62 ± 7.11 ml/kg/min) as obtained from the gas
analysis. Furthermore, significant differences (p ≤ 0.05) were observed between the direct and
indirectly predicted 2
VO values at levels 1-9 of the 20-m SRT compared to no significant
differences at levels 10 and 11 of the 20-m SRT.
In conclusion, to the researchers’ knowledge, this is the first study to develop valid 2max
VO
prediction functions from the use of several anthropometric measurements, physical and motorperformance
test results and demographic information for a group of South African adolescents.
Furthermore, this is also the first study to reveal that the 20-m SRT is not a valid test for the
accurate prediction of 2
VO and 2max
VO of a cohort of adolescent South African boys. The
results of this study may possibly allow practitioners in the field of Human Movement Science to
more accurately screen the indirect 2max
VO values of adolescents by making use of easily
obtainable measures and information, instead of the predicted 2max
VO values of the 20-m SRT / PhD (Human Movement Science), North-West University, Potchefstroom Campus, 2014
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:nwu/oai:dspace.nwu.ac.za:10394/11936 |
| Date | January 2014 |
| Creators | Pienaar, Cindy |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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