Better Health-Related Fitness in Youth: Implications for Public Health Guidelines Page: 380
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Int J Exerc Sci 10(3): 379-389, 2017
(12, 19). Santos and colleagues (19) reported that youth who were classified as meeting the
PAG and engaged in low levels of sedentary behavior (based on the median value for
sedentary time by age and gender) were more likely to achieve a criterion-referenced standard
for CRF. Although previous research findings from observational and experimental studies
indicates an association between PA and HRF, more information is needed regarding the exact
amount of activity (e.g., number of days with 60 minutes of aerobic PA) that is associated
with healthier levels of HRF. Thus, additional evidence on the doseresponse relationship
between the amount of PA and HRF outcomes is needed (9, 16).
The current PAG for children and adolescents is 60 minutes of daily PA, which should
include 3 days of musculoskeletal and bone-enhancing activities. Strong and colleagues (23)
provided support for this recommendation after conducting a systematic review of 850
articles. Strong et al.'s recommendation for 60 minutes of daily PA was largely based on the
results of intervention studies with overweight and obese children that revealed 30-45 minute
bouts of PA on 3-5 days per week improved various health outcomes (9). Sixty minutes of
daily PA was chosen to help account for inter- and intra-individual differences in response to
PA in free-living situations (9, 23). Strong and colleagues found strong evidence regarding the
amount of activity youth needed to improve health and behavioral outcomes, but Dietz (4)
indicated that there were still important gaps in the literature. Dietz emphasized that
investigating different types (e.g., aerobic PA) and doses (e.g., five times weekly) of PA would
likely have varying effects on adverse health outcomes. Addressing these gaps is important as
the PAG are currently being reviewed and potentially modified. While there are different
types of PA, aerobic PA was the primary focus of the current study because aerobic activities
are the most common and have the broadest physiological and health effects (8).
Previous research has indicated that aerobic PA can improve different aspects of HRF (14), but
limited information is available regarding the exact number of days of aerobic PA needed for
youth to achieve healthier HRF levels and how each additional day of aerobic PA affects
fitness outcomes. Further investigation will help identify the actual minimum number of days
needed to achieve a fitness level sufficient to accrue health benefits. Ortega and colleagues (15)
assessed the relationship between PA and CRF and found that 60 minutes or more of daily PA
was associated with higher CRF levels in youth. However, the participants were placed into
dichotomous groups based on those who achieved 60 minutes or more of daily PA and those
who did not over a 4-day period. Thus, there is currently a need for more information
regarding the number of days of aerobic PA that is associated with adolescents achieving HRF.
The purpose of this study was to expand on previous research using aerobic PA by
investigating the association between the number of days of aerobic PA and physical fitness
achievement based on the FitnessGram assessment (i.e., Progressive Aerobic Capacity
Endurance Run [PACER] laps, push-ups, curl-ups, trunk lift, and Body Mass Index [BMI]). It
was hypothesized that there would be a positive association between the number of days of
aerobic PA and each component of HRF (i.e., CRF, body composition, and muscular fitness).
International Journal of Exercise Science 380 http://www.intjexersci.com
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Barton, Mitch; Jackson, Allen W.; Martin, Scott B.; Morrow, James R.; Petrie, Trent A. & Greenleaf, Christy. Better Health-Related Fitness in Youth: Implications for Public Health Guidelines, article, April 4, 2017; Bowling Green, Kentucky. (digital.library.unt.edu/ark:/67531/metadc974451/m1/2/: accessed November 20, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT College of Education.