Course:KIN366/ConceptLibrary/Aerobic Fitness

Movement Experiences for Children
KIN 366
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Instructor:	Dr. Shannon S.D Bredin
Email:	shannon.bredin@ubc.ca
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Aerobic fitness, often used interchangeably with the term cardiovascular fitness, refers to the ability of an individual to take in oxygen from the environment, deliver it to the muscles, and use it to generate energy during exercise (Armstrong & Welsman, 2007). Aerobic means “in the presence of oxygen” in contrast to anaerobic, which means “in the absence of oxygen” (McDonald & Hodgdon, 1991). An individual’s aerobic fitness is influenced by several factors, some of which include genetics, lifestyle, and body size. In particular, an individual’s age and sex can cause major differences in aerobic fitness levels (Craig, Shields, Leblanc, & Tremblay, 2012; Ayres & Sariscsany, 2010).

Physical activity is different from aerobic exercise in that it is typically measured by the accumulation of activity level throughout the day across varying intensities (Goldfield, Adamo, Rutherford, & Murray, 2012). When the energy expenditure of the body is above a basal level, the bodily movement is considered physical activity (Lees and Hopkins, 2013). Aerobic exercise typically consists of a planned or structured session of activity for a specified duration and intensity (Goldfield et al., 2012). Aerobic fitness can be improved by aerobic physical activity (Goldfield et al., 2012).

Aerobic physical activity utilizes large muscle groups, can be performed for an extended period of time (8-10 minutes or more), and is rhythmic in nature (Malina, Bouchard, & Bar-Or, 2004; McDonald & Hodgdon, 1991). It is usually of light to moderate intensity and uses mainly the aerobic energy-generating process, where oxygen is needed to meet energy demands (Malina, Bouchard, & Bar-Or, 2004; McDonald & Hodgdon, 1991). Examples of aerobic physical activity include but are not limited to: jogging, swimming, cycling, skating, dancing, and walking (McDonald & Hodgdon, 1991). Aerobic based activities stress the cardiovascular and respiratory systems, and do so for a period of time long enough to lead to beneficial changes in the body (Janssen & LeBlanc, 2010; McDonald & Hodgdon, 1991).

How is it measured?

Aerobic fitness in adults is measured by maximal oxygen uptake (VO2 max), which is the maximum amount of oxygen that an individual can use to produce energy during physical activity (Ayres & Sariscsany, 2010). VO2 max values can be determined in labs using maximal exercise tests, but since this is not suitable for the general public, several sub-maximal aerobic fitness tests have been developed which allow for predictions of VO2 max from sub maximal heart rates (Ayres & Sariscsany, 2010). For healthy adults, VO2 max increases with increased fitness levels which shows a positive effect of exercise on aerobic fitness (Ayres & Sariscsany, 2010).

For children, if VO2 max is used as a measure of aerobic fitness, it is hard to determine how much of that is due to aerobic activity and how much of it is being influenced by other factors such as maturation, increase in body size, age, and heredity, which are all key contributing factors to a child’s aerobic fitness (Craig et al., 2012; Ayres & Sariscsany, 2010). For example, even a child who is slightly active could obtain a good score on an aerobic fitness test due to the influence of other factors (Ayres & Sariscsany, 2010). In addition, it is also well acknowledged that the intensity and duration of exercise required to obtain a VO2 max is rarely practiced in the every day lives of young people (Armstrong & Welsman, 2007).

For these reasons, although a VO2 max value can be obtained for a child, it is not generally done (Malina et al., 2004). Aerobic fitness can, however, still be measured and is done most commonly by the multistage 20-meter shuttle run test for kids of elementary school age (Léger, Mercier, Gadoury, & Lambert, 1988). Participants run back and forth on a 20-meter course and must touch the 20-meter line; at the same time, a sound signal is emitted from a prerecorded tape (Léger et al., 1988). The 20-meter shuttle run test can be used to predict maximal oxygen uptake (VO2 max) in children, by using the speed corresponding to the last stage reached by the child and age of the child (Léger et al., 1988). It has also been found to be a reliable test for maximal aerobic power of schoolchildren, healthy adults attending fitness class, and athletes performing in sports with frequent stops and starts such as basketball and fencing (Léger et al., 1988).

Growth-related adaptations

Changes occur both in a child’s heart and lungs during growth, which influences their oxygen uptake at a given work load (Malina et al., 2004). For example, an individual’s ability to take in oxygen from the environment, transport it, and use it within the body changes during the individual’s physical development. Aerobic fitness depends on the capacity of the individual’s heart and lungs to distribute oxygen-rich blood to working tissue, the ability of the cells of the tissue to remove and use the oxygen, and the ability of the circulatory system to return blood back to the heart (Ayres & Sariscsany, 2010). This capacity of a child’s heart and lungs is known to increase during growth (Malina et al., 2004).

Oxygen uptake (VO2) depends on heart rate, stroke volume, and the difference in O2 content in the arterial and mixed venous blood according to Fick’s equation, which is written as: VO2 = HR x SV(CaO2-CvO2) (Malina et al., 2004). This equation can be used to explain the changes in VO2 during growth. For example, due to the increase in heart size during growth, which is associated with an increase in body weight, stroke volume also increases during growth (Malina et al., 2004). Even though heart rate is known to decline during growth, the product of heart rate and stroke volume increases, which results in an increased VO2 (Malina et al., 2004). Similarly, an increased VO2 during exercise in children is the result of a higher arterio-venous difference in oxygen content, which means more oxygen is extracted from the blood at the same level of oxygen uptake (VO2) (Malina et al., 2004).

Heart size increases during growth, with the increase generally being proportional to body weight, but more so to fat-free mass (Malina et al., 2004). Starting from a volume of about 40cm³ at birth, heart volume doubles by 6 months, quadruples by 2 years, and gets to approximately 600-800 cm³ in young adulthood (Malina et al., 2004). Cross sectional studies have been done which compare the relationship between volume of the heart and maximal aerobic power during growth; they show that VO2 max is strongly correlated with the absolute size of the heart in children and adolescents (Malina et al., 2004). These studies show a linear relationship between heart volume and VO2 max such that an increase in heart volume results in an increased VO2 max (Malina et al., 2004).

As growth occurs in children, respiratory functions also mature (Malina et al., 2004). For example, human lungs, which weigh just 60-70 g at birth, increase in mass by about 20 times by the time maturity is reached (Malina et al., 2004). The heart grows roughly proportionally to body weight, while the lung grows roughly proportionally to height (Malina et al., 2004). Since respiratory functions include the transport of gases in the blood to and from tissues and the use of oxygen at the cellular level, both of which are related to aerobic fitness, the development of the respiratory system also contributes to an increase in aerobic fitness as a child grows (Malina et al., 2004).

Gender differences

VO2 max increases continuously until about 16 years of age for boys, while only until about 13 years of age for girls, after which it plateaus and remains at a plateau through adolescence (Malina et al., 2004). Absolute VO2 max values are typically higher in boys than in girls. This trend is present in all ages (Malina et al., 2004).

Trends

In a study done by Craig et al. (2012), changes in aerobic fitness among Canadian adults and children were determined. Aerobic fitness levels of both children and adults appear to have decreased over the past 3 decades (Craig et al., 2012). The aerobic fitness levels of Canadians were lower in 2007-2009 when compared to those in 1981, with the declines present in all ages and in both males and females (Craig et al., 2012). There are also decreases in strength, flexibility, and adiposity associated with lower aerobic fitness levels (Craig et al., 2012).

This study was done by comparing surveys from 1981 and 2007-2009, which were completed by participants between the ages of 8 through 69 years (Craig et al., 2012). These participants performed sub maximal step tests, which had age and sex specific exercise stages (Craig et al., 2012). For adults, VO2 max was estimated using prediction equations; for children, VO2 max was predicted to be at a heart rate of 200 beats/min (Craig et al., 2012).

The decreases in aerobic fitness are significant and of particular concern to young people (Craig et al., 2012). Lower fitness is associated with increased cardiovascular disease risk factors in boys and girls (Kwon, Burns, & Janz, 2010; Tomkinson, 2011). This study suggests that contemporary children and youth have a higher risk for certain diseases compared with their peers from 25–30 years ago; as they move into adulthood, they may achieve poorer health outcomes than do adults today Craig et al. (2012).

There is a simple solution that can be practiced, as supported by research in the field. A strong positive relationship exists between aerobic physical activity and aerobic fitness in adults, (Rowlands, Eston, and Ingledew, 1999; Ayres & Sariscsany, 2010). Only a small to moderate relationship was found to exist in children and youth (Rowlands et al., 1999). However, it is important to keep in mind that activity levels are known to track from childhood to adulthood (Ayres & Sariscsany, 2010). If children are active starting from a young age, they will grow up to be active adults (Ayres & Sariscsany, 2010). Based on these studies, the current trend can be improved if an intervention is started that targets not just adults, but more importantly, young children.

Health Benefits

An increase in aerobic fitness leads to many beneficial outcomes for youth including:

Increases in standardized academic achievement scores (Hillman et al., 2009)
Higher academic performance and plans for higher education (Kantomaa, Tammein, Demakakos, Ebeling, & Taanila, 2010)
Decreased depression and anxiety (Ekeland, Heian, & Hagen, 2005; Larun, Nordheim, Ekeland, Hagen & Heian, 2006)
Improvements in physical self perception and self esteem in obese youth (Daley, Copeland, Wright, Roalfe, & Wales, 2006)
Beneficial effects on adiposity in overweight or obese children/youth but also those with normal body weight (Goldfield et al., 2012)
Beneficial effects on plasma lipid and lipoproteins levels (Goldfield et al., 2012)

Other benefits associated with aerobic fitness as suggested by Cooper (1982, p. 107) include:

Higher levels of energy and for longer periods of time
Bone strength that continues with age
Better and more effective sleep
Increased productivity
Improved digestion and control of constipation.

Clearly, an increase in aerobic fitness has numerous health benefits. Children can greatly benefit from aerobic fitness in other domains of their life. There should be strategies and ways to increase the aerobic fitness levels in children.

Practical applications

Prescription

Physical activity in general is associated with numerous health benefits. Janssen and LeBlanc (2010) advise that even modest amounts of activity could help achieve health benefits. Although it is recommended by Janssen and LeBlanc (2010) that children and youth between the ages of 5 and 17 should get an average of at least 60 minutes a day of light-moderate intensity physical activity, it should be remembered that a smaller amount or duration will be beneficial (Janssen & LeBlanc, 2010). The aim, therefore, should be to work towards leading an active lifestyle, in which physical activity can even be attained in bouts of as small as 5 to 10 minutes (Janssen & LeBlanc, 2010). For individuals, families, and communities, this can take place in the form of active transportation, experiencing the great outdoors, or playing a short game that encourages physical movement and activity.

Aerobic-based physical activities of light to moderate intensity that stress the cardiovascular and respiratory systems are known to have the greatest health benefits, therefore, it is recommended that the majority of physical activity that a child should try to attain should be aerobic based (Janssen & LeBlanc, 2010).

Recommendations to parents and teachers

For young children in elementary school, participation in aerobic activity should be emphasized and encouraged instead of getting high aerobic test scores (Ayres & Sariscsany, 2010). Since regular moderate to vigorous activity will provide benefits to the child, the high or low test scores are not a significant part of the big picture (Ayres & Sariscsany, 2010).

To ensure adherence in children, it is recommended to teachers and parents that they make sure the aerobic exercise their kids are doing do not burn them out by causing extreme fatigue or soreness (Ayres & Sariscsany, 2010). Likewise, adult exercise training prescription involving the FITT principle should not be used for children (Ayres & Sariscsany, 2010). Emphasis should instead be placed on promoting and encouraging a physically active lifestyle through fun and enjoyable methods. These methods should be age specific and appealing to those specific age groups. They can revolve around unstructured and structured play, as well as individual and team sports.

Aerobic fitness can be incorporated into classrooms in many different ways. Teachers and educators may use the different subjects of the curriculum to relate to aerobic physical activity (Ayres & Sariscsany, 2010). For example, younger students in math class can be taught to record, add up and chart the number of minutes they are active during lunch/recess time, after school and in physical education class (Ayres & Sariscsany, 2010). Older kids can calculate target heart rate and set a goal to be within that target range during activity (Ayres & Sariscsany, 2010). In science, it can be taught how blood flows through the body during exercise; in language arts, kids can be encouraged to write about their favorite physical activity they have participated in (Ayres & Sariscsany, 2010). Through these methods, in an age appropriate manner, the importance of aerobic fitness can be taught and an active lifestyle can be encouraged and emphasized starting from a young age.

Safety guidelines

Children respond to exercise differently than adults do, due to physiological characteristics of the body. When trying to increase the aerobic fitness of children, there are key characteristics to pay attention to as suggested by Bar-Or (1984) and Rowland (1996) such as:

(The list below is taken directly as cited in Ayres & Sariscsany, 2010, p. 91)

Children are less economical and use more oxygen than adults do at any given submaximal exercise intensity
Children’s heart rates are generally higher than those of adults at rest and across all levels of exercise
Children hyperventilate during exercise more than adults do
Children fatigue sooner than adults do when exercising in heat
Children sweat less than adults do and therefore have difficulty using evaporation as a method of heat dissipation

For these reasons, care should be taken to ensure a child is not over-worked. Breaks can be taken to ensure a child is properly nourished, replenished, and ready to meet the demands of aerobic activity.

Future Research

Future work in the field can focus on aerobic fitness promotion strategies that can involve the socio-ecological model of health. Looking into communities and schools, there are many roles that different people can play in a child’s development. Developing standardized testing methods across studies could be useful to accurately assess aerobic fitness across countries (Craig et al., 2012). Normative data from such studies would provide fitness standards to assess whether children and youth are meeting developmental milestones (Craig et al., 2012).

References

Armstrong, N., & Welsman, J. (2007). Aerobic fitness: What are we measuring? Pediatric Fitness, 50, 5. doi:10.1159/000101073

Ayres, S.F., & Sariscsany, M.J. (Eds.). (2010). Physical education for lifelong fitness: The physical best teacher’s guide (3rd ed.). Champaign, IL: National Association for Sport and Physical Education.

Cooper, K. H. (1982). The aerobics program for total well-being: Exercise, diet, emotional balance. New York: M. Evans.

Craig, C. L., Shields, M., Leblanc, A. G., & Tremblay, M. S. (2012). Trends in aerobic fitness among canadians, 1981 to 2007–2009. Applied Physiology, Nutrition, and Metabolism, 37(3), 511-519. doi:10.1139/h2012-023

Daley, A. J., Copeland, R. J., Wright, N. P., Roalfe, A., & Wales, J. K. H. (2006). Exercise therapy as a treatment for psychopathologic conditions in obese and morbidly obese adolescents: A randomized, controlled trial. Pediatrics, 118(5), 2126-2134. doi:10.1542/peds.2006-1285

Ekeland, E., Heian, F., & Hagen, K. B. (2005). Can exercise improve self esteem in children and young people? A systematic review of randomised controlled trials. British Journal of Sports Medicine, 39(11), 792-798. doi:10.1136/bjsm.2004.017707

Goldfield, G.S., Adamo, K.B., Rutherford, J., & Murray, M. (2012). The effects of aerobic exercise on psychosocial functioning of adolescents who are overweight or obese. Journal of Pediatric Psychology, 1-12, doi:10.1093/jpepsy/jss084

Hillman, C. H., Pontifex, M. B., Raine, L. B., Castelli, D. M., Hall, E. E., & Kramer, A. F. (2009). The effect of acute treadmill walking on cognitive control and academic achievement in preadolescent children. Neuroscience, 159(3), 1044-1054. doi:10.1016/j.neuroscience.2009.01.057

Janssen, I., & LeBlanc, A. G. (2010). Systematic review of the health benefits of physical activity and fitness in school-aged children and youth. International Journal of Behavioral Nutrition and Physical Activity, 7(40), 1-16. doi: 10.1186/1479-5868-7-40

Kantomaa, M. T., Tammelin, T. H., Demakakos, P., Ebeling, H. E., & Taanila, A. M. (2010). Physical activity, emotional and behavioural problems, maternal education and self-reported educational performance of adolescents. Health Education Research, 25(2), 368-379. doi:10.1093/her/cyp048

Kwon, S., Burns, T. L., & Janz, K. (2010). Associations of cardiorespiratory fitness and fatness with cardiovascular risk factors among adolescents: The NHANES 1999-2002. Journal of Physical Activity & Health, 7(6), 746.

Larun, L., Nordheim, L. V., Ekeland, E., Hagen, K. B., & Heian, F. (2006). Exercise in prevention and treatment of anxiety and depression among children and young people. The Cochrane Database of Systematic Reviews, (3), CD004691.

Lees, C., & Hopkins, J. (2013). Effect of aerobic exercise on cognition, academic achievement, and psychosocial function in children: A systematic review of randomized control trials. Preventing Chronic Disease, 10. http://dx.doi.org/10.5888/pcd10.130010

Léger, L. A., Mercier, D., Gadoury, C., & Lambert, J. (1988). The multistage 20 metre shuttle run test for aerobic fitness. Journal of Sports Sciences, 6(2), 93.

Malina, R. M., Bouchard, C., & Bar-Or, O. (2004). Growth, maturation, and physical activity. Champaign, Ill: Human Kinetics.

McDonald, D. G., & Hodgdon, J.A. (1991). The psychological effects of aerobic fitness training: Research and theory. New York, NY: Springer-Verlag.

Rowlands, A.V., Eston, R.G., & Ingledew, D.K. (1999). Relationship between activity levels, aerobic fitness, and body fat in 8-to-10-yr-old children. Journal of Applied Physiology, 86(4), 1428-1435.

Tomkinson, G. (2011). Aerobic fitness thresholds for cardio metabolic health in children and adolescents. British Journal of Sports Medicine, 45(9), 686-687. doi:10.1136/bjsm.2009.069815