Growing evidence has been amassed over the past two decades that exercise may promote improvements in mental function, particularly those cognitive processes termed executive functions, which are involved in behavioural control and self-regulation. These functions involve working memory, response inhibition and cognitive flexibility. Recently, much has been made of the importance of the role of executive processes in daily life and how they benefit children’s adaptive behaviours, intellectual functioning and academic success.1

Moderate-intensity aerobic exercise (running, cycling, swimming) for approximately 30 minutes facilitates cognitive performance, a potent mediator of this effect being exercise-induced physiological arousal. A randomised controlled trial conducted in 2014 by Hillman et al, designed to meet current  paediatric recommendations of 60 minutes of moderately vigorous physical activity daily, used behavioral and electrophysiological measures of brain function to demonstrate enhanced attentional inhibition and cognitive flexibility among prepubertal children.2 The physical activity does not necessarily have to be strenuous to be beneficial; a study by Chang et al of the impacts of coordinative exercise on executive function in kindergarten children revealed that exercise intervention, regardless of intensity, resulted in shorter reaction times and higher response accuracy and may specifically benefit executive function.

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Considerable evidence has revealed that systematic exercise can result in improved blood flow and oxygen availability to the brain, and aerobic exercise training has been shown to beneficially alter the structure and function of the brain.4 Team games such as basketball or volleyball may have the added benefit of promoting mental engagement, which primes memory encoding5, in addition to capitalising on social interactions among children and teachers, which may also enhance cognitive and affective self-regulation.

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Cognisant of the cognitive benefits of exercise, teachers have even taken it into the classroom. TAKE-10! ®, an activity program developed by the International Life Sciences Institute (ILSI)6 , incorporates physical movements designed to solidify specific academic contexts (e.g. jump-rope actions linked to learning basic mathematics), and has been found to improve children’s academic performance and in-class behaviour.7

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Despite the perks, not all Singaporean children are exercising optimally. In 2006, Wang, Chia and Quek reported that 66% of boys and 57% of girls met the recommended levels of daily physical activity for children8. Another study by Chia M in 2010 noted that daily step counts fell short by up to 35% of the 16,000 and 13,000 recommended respectively for male and female youths9.

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In the local as well as global context, outdoor playtime is frequently ousted by screen time. Across the industrialised world, watching screen media is the main pastime of children. Children routinely engage in two or more forms of screen viewing simultaneously, such as the television and the laptop computer10. Viewing is also starting earlier in life; nearly one in three American infants has a TV in their bedroom, and almost half of all infants watch TV or DVDs for nearly 2h/day11. Excluding any viewing time outside the home, such as hand-held screen activities, average screen time in the home has been reported to be 7.8 hours/day for Canadian children12 and 6.1 hours /day for British children13. This has undoubtedly contributed to the exponential rise in childhood obesity and its sobering metabolic consequences.

Irrespective of the content or educational value of what is being viewed, the sheer amount of average daily screen time during discretionary hours after school is increasingly being considered an independent risk factor for disease. In children and adults, screen time has been found to have an unfavourable dose-response association with a range of biomarkers for cardiovascular disease, type 2 diabetes mellitus and metabolic syndrome, including levels of low-density lipoprotein (LDL), total cholesterol, triglycerides, fibrinogen, C-reactive protein and systolic/diastolic blood pressure14-15.  Additionally, children’s screen time may be distinct from other forms of sedentary behaviour in its influence on biological risk factors for disease. Gopinath et al examined a range of sedentary behaviours, screen activities and blood pressure in young adolescents and reported a dose-response relationship – each hour per day spent in screen time, watching television and playing video games was associated with a significant increase in diastolic blood pressure of 0.44 (p=0.0001), 0.99 (p<0.0001) and 0.64 mm Hg (p=0.04), respectively, while by contrast, each hour spent reading per day was associated with a decrease.16

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The associations between screen time and health risks are reported to occur generally beyond exposure of 2h/day. Additionally, 80% of adult brain size growth occurs during a child’s first three years, when they may be most vulnerable to the effects of screen media. Ideally, screen viewing should be delayed or minimised until the age of three years. Subsequently, suggested discretionary screen time limits are based on age17:

• 3-7 years: 0.5-1h/day

• 7-12 years: 1h

• 12-15 years: 1.5h

• 16+ years: 2h

One alternative that has been explored to reduce morbidity in children who find it difficult to reduce screen time is Exergames, which are computer-based games that require children’s physical activity to control game conditions, and have been found to facilitate children’s cognitive test performance.18 However, in view of the possible adverse effects of excessive screen time, these electronic aids to exercise should be used sparingly despite their benefits, and children should be encouraged to participate in real-life activities.

Exercise is also known to be protective against myopia, a common problem among Singaporean children. Studies in children have indicated an association between physical activity/outdoor activity and refractive error19-21, and it has been observed that myopes spend significantly less time engaged in sports, which is associated with myopia.21 To study the effect of physical activity on myopia, a 2-year longitudinal cohort study was carried out on 156 Caucasian medical students from the University of Copenhagen, Denmark, from 2005 to 2007.22 The results of the study showed an association between physical activity and myopia that suggested a protective effect of physical activity on the development and progression of myopia.

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Mindful of the health risks that excessive screen time and lack of outdoor play make children vulnerable to, KKH Sports Medicine Programme has developed various exercise programmes for children aged 4- 18 years old. The programmes are designed to improve physical fitness and overall function for children with varying health conditions, including obesity, respiratory disease, congenital heart disease, epilepsy, behavioural and developmental problems. Once a child is referred, they will complete a standardised fitness assessment before enrolling into a customised exercise program. Our team of exercise specialists have vast experience in working with children and adopt a holistic, fun and developmentally appropriate approach to motivate children to be active. A doctor’s referral is required for a child to enrol in this programme. For children who are currently seeing a paediatrician at KK Women's and Children's Hospital, the referral may be made through the child’s paediatrician. For other program or referral enquiry, kindly contact Mr. Brandon Feng at email: sportsmed@kkh.com.sg.

References

1. Tomporowski PD, McCullick B, Pendleton DM, Pesce C. Exercise and children’s cognition: The role of exercise characteristics and a place for metacognition. Journal of Sport and Health Science 2015; 4:47-55.

2. Hillman et al. Effect of the FITKids randomized controlled trial on executive control and brain function. Pediatrics 2014;134(4):e1063-71.

3. Chang YK, Tsai YJ, Chen TT, Hung TM. The impacts of coordinative exercise on executive function in kindergarten children: an ERP study.Exp Brain Res 2013 ; 225:187-96.

4. Hillman CH, Erickson KI, Kramer AF. Be smart, exercise your heart: exercise effects on brain and cognition.Nat Rev Neurosci 2008; 9:58-65.

5. Pesce et al.Physical activity and mental performance in preadolescents: effects of acute exercise on free-recall memory. Ment Health Phy Act 2009;2:16-22.

6. International Life Sciences Institute. Childhood Obesity – advancing prevention and treatment: an overview for health professionals. Washington, DC: International Life Science Institute; 2003.

7. Kibbe et al. Ten years of TAKE 10! ®: integrating physical activity with academic concepts in elementary school classrooms.Prev Med 2011; 52:S43-50.

8. Wang C, Chia Y, Quek JJ. Patterns of physical activity, sedentary behaviours and psychological determinants of physical activity among Singaporean school children.  International Journal ofSports and Exercise Psychology 2006;4(3):227-49.

9. Chia M. Pedometer-assessed physical activity of Singaporean youths. Preventive Medicine 2010;50(5-6):262-4

10. Jago R et al.  ‘I’m on it 24/7 at the moment’: a qualitative examination of multi-screen viewing behaviours among UK 10-11-year olds.Int J Behav Nutr Phys Activ 2011;8:85.

11. Common Sense Media. Zero to Eight: Children’s Media Use in America. 2011. http://www/commonsensemedia.org/sites/default/files/research /zerotoeightfinal2011.pdf.

12. Leatherdale ST, Ahmed R. Screen-based sedentary behaviours among a nationally representative sample of youth: are Canadian kids couch potatoes? Chron Dis Injuries Canada 2011;31:141-6.

13. OfCom. Children and parents: media use and attitudes report. 2011. http://stakeholders.ofcom.org.uk/binaries/research/media-literacy/oct2011/Children_and_parents.pdf.

14. Wijndaele et al.Television viewing and incident cardiovascular disease: prospective associations and mediation analysis in the EPIC Norfolk study. PLoS ONE 2011;6:e20058.

15. Pinto Pereira SM, Ki M, Power C. Sedentary behaviour and biomarkers for cardiovascular disease and diabetes in mid-life: the role of television-viewing and sitting at work.PLoS ONE 2012;7:e31132.

16. Gopinath et al.Relationship between a range of sedentary behaviours and blood pressure during early adolescence. J Hum Hypertens 2011;26:350-6.

17. Sigman A. Time for a view on screen time.Arch Dis Child 2012;97(11):93542.

18. Best JR. Exergaming immediately enhances children’s executive function.Dev Psychol 2012; 48:1501-10.

19. Parssinen O, Era P, Leskinen AL. Some physiological and psychological characteristics of myopic and non-myopic young men. Acta Ophthalmol Suppl. 1985;173:85–87.

20. Parssinen O, Lyyra AL. Myopia and myopic progression among schoolchildren: a three-year follow-up study. Invest Ophthalmol Vis Sci. 1993;34:2794–2802.

21. Mutti DO, Mitchell GL, Moeschberger ML, Jones LA, Zadnik K. Parental myopia, near work, school achievement, and children's refractive error. Invest Ophthalmol Vis Sci. 2002;43:3633–3640.

22. Jacobsen N, Jensen H, Goldschmidt E. Does the level of physical activity in university students influence development and progression of myopia? a 2 year prospective cohort study. Invest Ophthalmol Vis Sci. 2008;49 (4:1322–1327.