Professor Neil Armstrong

Neil Armstrong is Professor of Paediatric Physiology and Director of the Children’s Health and Exercise Research Centre at the University of Exeter. Neil trained at Loughborough College and spent 5 years teaching in schools before moving into lecturing. His research interests lie in paediatric physiology and the promotion of children's health and well-being and he has published 7 books and over 300 other papers on these topics. He is a former President of the Physical Education Association of the United Kingdom and he was founder editor of the European Journal of Physical Education.

PHYSICAL FITNESS, PHYSICAL ACTIVITY AND PHYSICAL EDUCATION

Neil Armstrong
Children's Health and Exercise Research Centre, University of Exeter, UK.

Correspondence to:

Professor Neil Armstrong
Children's Health and Exercise Research Centre
School of Postgraduate Medicine and Health Sciences
University of Exeter
EXETER, EX1 2LU, U.K.
Telephone: +1392 264812
Fax: +1392 264706
email: N.Armstrong@exeter.ac.uk
www: http://www.exeter.ac.uk/cherc/

A sedentary adult lifestyle is associated with all-cause mortality. The effect of regular physical activity in promoting aerobic fitness, increasing muscle strength, improving blood lipids, reducing high blood pressure, decreasing the risk of colon cancer, countering obesity, retarding osteoporosis, enhancing blood glucose control and raising psychological well-being is extensively documented (36). The health benefits of physical activity during childhood and adolescence have been studied less frequently but appropriate physical activity during youth has been demonstrated to promote skeletal health, reduce body fatness, increase aspects of health-related fitness, and enhance psychological well-being (8,10). Furthermore, there is a growing conviction that adults' health and well-being has its origins in behaviour established during childhood and adolescence and that inactive young people are unlikely to become physically active adults (1).

This paper will review young people's physical fitness and physical activity patterns in the light of current recommendations for health-related behaviour and explore the role of physical education in promoting and fostering active lifestyles.

Are Young People Fit?

Physical fitness is a complex phenomenon which is extremely difficult to define. Due to time constraints, in this presentation I will focus upon arguably the most important component of physical fitness, aerobic (or cardiovascular) fitness. Aerobic exercise is dependent upon pulmonary, cardiovascular and haematological components of oxygen delivery and the oxidative mechanisms of the exercising muscles. As maximal exercise is limited by peak oxygen uptake (peak VO2 ) this parameter is widely recognized as the best single index of aerobic fitness (11). The measurement of peak VO2 requires the child to exercise to exhaustion while his/her oxygen consumption is monitored. Reliable data on children under the age of 8 years are difficult to obtain and I will therefore limit my discussion to the more secure database of young people aged 8 to 16 years.

Peak VO2 demonstrates a progressive rise in relation to chronological age in both boys and girls. At the beginning of secondary school (11 years of age) boys' peak VO2 is about 18% higher than that of girls, probably due to boys' larger stroke volume during exercise. As sex differences in muscle mass and haemoglobin manifest themselves the sex difference in aerobic fitness increases to about 37% by the end of compulsory secondary education (12).

To compare the peak VO2 of young people of different body size it is conventional to express peakVO2 in ratio with body mass. When aerobic fitness is expressed in this manner a different picture emerges. Boys' mass-related peak VO2 remains stable from childhood through adolescence whereas in girls a gradual deterioration in peak VO2 can be observed. Using this conventional analysis maturation has been demonstrated to exert no additional influence on peak VO2 above that "caused" by growth. However, in a number of publications we have demonstrated that the use of the ratio method to control for body size has clouded our understanding of the independent contributions of age and maturity to the growth of peak VO2 (9,11,12). With body size appropriately controlled for, using either allometric scaling (13,37) or multilevel modelling (12,14), boys' peak VO2 increases through childhood and adolescence and into early adulthood. Girls' peak VO2 rises into puberty and then levels off as they approach young adulthood. Maturation induces increases in peakVO2 in both sexes independent of those explained by body size and age.

There is no scientific evidence to suggest that children's and adolescents' aerobic fitness has declined over the last 60 years and an analysis of data reported since the pioneering work of Robinson (29) reveals a remarkable consistency over time in young people's peak VO2 (9,10; and see 15 for data on Hong Kong children). There is no consensus on levels of optimal aerobic fitness for young people but members of the European Pediatric Work Physiology Group (16) have expressed the view that there is a lower limit of peakVO2 that, in the absence of other health-related problems, may represent a "health risk". Few studies have reported their data in sufficient detail to estimate the number of children and adolescents below this level of aerobic fitness but a re-analysis of the peak VO2 scores of over 3,000 young people who have been tested in my Centre over the last 13 years revealed that less than 2% of the values fell below the proposed "health-risk" threshold.

Are Young People Active?

The problems associated with monitoring young people's physical activity patterns have been well-documented and although more than 30 methods of assessing physical activity have been utilized the validity of many of these techniques has not been established with children and adolescents. The technique used must be socially acceptable, it should not burden the young person with cumbersome equipment, and it should minimally influence his/her normal physical activity patterns. The most accurate estimates of physical activity come from objective methods used over several days and a minimum monitoring period of three days has been recommended. Yet, regardless of the methodology adopted data are remarkably consistent over a number of countries (reviewed in 7 and 10; see 25 for data on Hong Kong children).

Neither the minimal nor the optimal amount of physical activity for young people can be precisely defined at this time and whether children or adolescents are classified as "active" or "inactive" depends upon the activity criteria implemented. Two recent Consensus Conferences (27,30) have provided useful recommendations. The National Institutes of Health (27) recommended that, "all children and adults should set a long-term goal to accumulate at least 30 minutes or more of moderate intensity physical activity on most, or preferably all days of the week" (p 243). The International Consensus Conference on Physical Activity Guidelines for Adolescents (30) recommended that, in addition to a minimal amount of daily physical activity (ie 30 min of moderate-intensity physical activity), "adolescents should engage in three or more sessions per week of activities that last 20 minutes or more at a time and that require moderate to vigorous levels of exertion" (p 308). Moderate activity was defined as equivalent to brisk walking and vigorous activity was defined as equivalent to jogging.

To estimate how many young people satisfy the above recommendations I will outline our observations of minute by minute heart rate monitoring from 0900 to 2100 of 839 5 to 16-year-olds over a minimum of three normal weekdays. In addition, 366 youngsters were also monitored for the same period on a Saturday (summarized in (3,4,10)). To interpret the heart rate data a representative sample of 100 young people exercised at various speeds on a horizontal treadmill. It was noted that, regardless of age, brisk walking and jogging generated steady-state heart rates of about 140 and 160 beats·min., respectively. Moderate physical activity (equivalent to brisk walking) was therefore defined as eliciting a heart rate ³ 140 beats·min. and vigorous physical activity (equivalent to jogging) was defined as eliciting a heart rate ³ 160 beats·min.

. The majority of primary schoolchildren met the NIH (27) recommendation of accumulating at least 30 minutes per day of moderate intensity physical activity. Nevertheless, it was demonstrated that at all ages more boys than girls met the NIH target and that there was a steady decline with age throughout the primary school period. At age 10 years about 85% of boys and 72% of girls achieved the NIH target. However, during the secondary school period there was a dramatic decline in the percentage of both sexes accumulating 30 minutes of moderate intensity physical activity per day with less than 20% of girls and less than 30% of boys meeting the target at age 14 years.

Sustained 20 minute periods of either moderate or vigorous physical activity were sparse in all age groups. Eighty four percent of girls and 77% of boys did not experience a single sustained 20 minute period with their heart rate greater than 160 beats·min-1 . Less than 3% of boys were observed to experience the equivalent of a daily 20 minute period with their heart rate greater than 160 beats·min-1 . Of the 459 girls monitored for three weekdays and the 195 girls monitored on a Saturday, not a single girl experienced the equivalent of a daily 20 min period of vigorous physical activity. Even 10 minute periods of moderate intensity physical activity were rarely experienced by significant numbers of young people demonstrating that sustained periods of physical activity do not characterize young people's physical activity patterns.

We can therefore conclude that many children and adolescents seldom experience the intensity and duration of physical activity recommended for health-related outcomes. Regardless of how the data are analysed, it appears the boys are generally more active than girls from an early age and that the activity levels of both sexes decline with age. A marked deterioration in physical activity is typical of both boys and girls as they move through secondary school.

There are no reliable data on children's and adolescents' physical activity patterns which pre-date 1980, however, an analysis of historical data on energy intake is of interest. Durnin (18) pooled data collected from the 1930s to the 1980s and demonstrated a progressive decrease in the energy intake of adolescents in the United Kingdom. The body mass of the young people had not decreased and the methodology of data collection was consistent. The only conceivable explanation for the reduction in energy intake, which must reflect diminished energy expenditure, is that adolescents' physical activity has decreased over the last 50 years.

Do Active Children Become Active Adults?

The view that high levels of physical activity during childhood increase the likelihood of such participation as an adult has often been advanced. The hypothesis is intuitively plausible but the definitive study of physical activity tracking from childhood through adult life has yet to be carried out.

A recent English national survey of adults' fitness and physical activity reported that 25% of those active when aged 14 to 19 years were classified as "very active" adults compared with only 2% of adults classified active now who were inactive at the earlier age (1). Thirty percent of the 6,000 adults surveyed were consistently in the same activity band at ages 14 to 19, 20 to 24 and their present age, thus indicating that adult activity patterns may have their origins in behaviour established during childhood and adolescence.

Three recent prospective studies have supported physical activity tracking (20,22,28). Kuh and Cooper (22) examined the physical activity patterns of more that 3,300 men and women aged 36 years, who were members of the 1946 British national birth cohort study. They reported that adolescent characteristics which were positive predictors of high sporting activity during adult life included above average ability at school games and teacher assessed high energy expenditure at age 13 years. In a smaller Swedish study 62 males and 43 females were required to complete a questionnaire concerning physical activity during their leisure time at the ages of 16 years and 27 years (20). At the age of 16 years the subjects also underwent a series of physiological tests. The investigators reported that the major portion of the variation in level of physical activity in the women, but not in the men could be predicted from physical characteristics, physical performance and activity levels at 16 years of age

. Perhaps the most persuasive evidence in support of physical activity tracking has emerged from a study of 961 Finnish youngsters, aged 12 years, 15 years or 18 years at baseline, who were followed for 6 years (28). Physical activity was assessed with a standardised questionnaire and an index was derived from the product of intensity, frequency and duration of leisure time physical activity. Significant tracking of physical activity was observed with 3 year correlations of the index ranging from 0.35 to 0.54 in boys and from 0.33 to 0.39 in girls. Tracking was better in older age groups. Approximately 57% of those initially classified as inactive remained inactive after a 6 year follow-up. The authors concluded that the level of physical activity tracks significantly from adolescence to young adulthood and that physical inactivity shows better tracking than does physical activity.

In summary, there is no scientific evidence to suggest that young people have low levels of aerobic fitness or that aerobic fitness has deteriorated over the last 60 years. Boys have higher levels of aerobic fitness than girls, at least from about 10 years of age, and sex differences increase as young people move through adolescence. However, sedentary lifestyles appear to be common and indirect evidence suggests that young people's energy expenditure has decreased over the last 60 years. Boys are more active than girls and girls' activity levels decline more rapidly than those of boys as they move from childhood through adolescence. No prospective study has followed children into adult middle age and beyond but the available evidence suggests that adult physical activity patterns may be established during childhood and adolescence. In particular physical inactivity tracks from childhood into adult life.

Promoting Physical Activity

The myriad interacting factors which may influence young people's physical activity are not fully understood but the consensus view is that no single correlate explains physical activity behaviour. Although acknowledging that physical activity behaviour is influenced by a variety of social variables and role models, I will focus on the role of the school and, in particular, physical education in promoting active living. This section is drawn from a more wide ranging discussion available elsewhere (10).

All children attend school from an early age and the school setting provides perhaps the most promise for influencing young people's physical activity behaviour. A number of school-based intervention programmes have been mounted with the objective of increasing children's physical activity but they have met with only limited success, sometimes because they were geared towards an outcome of enhancing physical fitness (reviewed in 31).

In schools, physical activity should not be divorced from other aspects of a healthy lifestyle and special provision should be made for a "whole school" cross-curricular approach to promoting healthy lifestyles. Science, home economics, physical education, health education, school meals, and school nursing staff should all be involved in a multidisciplinary, integrated approach.

The school should explore ways of using resources such as playgrounds and of making equipment (eg jump ropes) available at breaktimes in order to promote equitable physical activity which is not dominated by boys' games. Partnerships with families, physicians, and community organizations should be developed, facilities shared where appropriate, and school policy should be sensitive not only to current but also to post-school physical activity needs of its pupils.

The value of promoting enjoyable early life experiences of physical activity has been supported by several studies and primary school physical education is therefore a potentially important vehicle for fostering an appreciation of physical activity. The primary school should provide an ideal environment for promoting an active lifestyle but concerns have been expressed, at least in the UK, over facilities for physical education and access to fully qualified physical education teachers (17). In primary schools it is unlikely that specialist physical education teachers will always be available but at the very least each school should identify a physical education curriculum leader with responsibility for the subject. The curriculum leader's continuing professional development in the subject should be supported through in-service courses and visiting specialists.

The primary school physical education curriculum which tends to focus upon individual motor skills and co-operative rather than competitive activities is generally very popular with children. Concerns have been expressed over the activity content of physical education lessons (26,32) and although there appear to be no significant gender differences in physical activity during structured aspects of lessons girls have been observed to be less active than boys during free play within lessons (24). However, although the provision of a high activity content should be an important component of physical education lessons it is much more important to build a foundation of motor skills and to make children's early activity experiences enjoyable in order to foster future participation.

The moderate to vigorous physical activity content of secondary school physical education lessons has been questioned (21) but it appears that curriculum content and enjoyment and not high activity content are the most influential factors in developing positive or negative attitudes towards physical education (23). These factors appear to be particularly important to females less inclined to physical activity and point to the need to create programmes that capture students' interest.

Young people should be encouraged to internalise the motivation to be active so that when the extrinsic motivation of the teacher is removed they will continue with an active lifestyle. To achieve "activity independence" children and adolescents need to understand the principles underlying healthy activity and be taught how to become informed decision makers who can plan and implement individual activity programmes that can be periodically reappraised and modified as they get older.

Competitive team games dominate the secondary school physical education curriculum in most European countries despite unequivocal evidence to show that, with the possible exception of football for boys, they are not transferring to out of school participation (33,34). Competitive team games are a valuable component of the physical education curriculum. Many youngsters enjoy team sport and should be given the opportunity to fulfil their potential but young people need to be exposed to a balanced programme of competitive, co-operative, individual, partner, and team activities, thus laying the foundation for present and future physical activity behaviour. A competitive approach tends to focus on the few students with high ability and may alienate the majority of young people. Early maturing boys tend to excel but there is no evidence to suggest that early specialization is necessary for the nurturing of sporting talent. In fact early specialization may turn young people off lifetime physical activity, especially if through extrinsic teacher/coach domination they have not achieved "activity independence" (2).

A competitive ethos appears to be acceptable to most boys but, notably, less acceptable to low-exercising boys (19). Many girls reject competition, even the high exercisers. Individual sports and activities are far more popular with girls than competitive team games (33). The dislike of many girls for team games should not be confused with disinterest in physical activity but team game dominance of the curriculum may well contribute to girls' low levels of physical activity. Physical educators need to take a reflective view of the balance, organization and presentation of their programmes in order to challenge the gender ideologies reflected in many physical education curricula (6).

Despite a recent and overdue change in emphasis from physical fitness to physical activity in physical education programmes many secondary schools still include compulsory fitness testing within their curriculum Yet, tests that are suitable for use in the school environment and that provide valid and objective measures of fitness are not available. Fitness tests simply determine the obvious, at best only distinguishing the mature and/or motivated child from the immature and/or unmotivated child (5). The use of norm tables confounds the issue of relative fitness because tables constructed on the basis of chronological age cannot be used to legitimately classify children at different levels of maturity. Furthermore, having different norms for boys and girls results in different expectations. Norms are based on performances rather than capabilities and if teachers accept lower norms for girls as reflecting acceptable performances, girls will tend to meet these lower expectations (35). Students generally view fitness testing unfavourably and a major contribution to negative attitudes towards physical education (23). Teachers must ask themselves why they are testing children's fitness, and if the answer is to classify children, then perhaps they would be better employed seriously addressing the problem of children's sedentary lifestyles.

Other factors which may provide barriers to adopting active lifestyles include the availability of private showering activities and the compulsory wearing of perceived unattractive "gym kit". Clothing has been identified as a determinant of negative attitudes for both males and females but it is a major problem for some girls since notions of femininity and body image are more intensely bound together for them. Looking good remains a significant motivator for girls' participation in physical activity. A dialogue between staff and students should be able to solve this perceived problem.

Summary

There is little evidence to suggest that young people are unfit or that aerobic fitness has decreased over the last 60 years. However, many children and adolescents have sedentary lifestyles. Boys are more physically active than girls during childhood and girls' activity levels decline more rapidly than those of boys as they progress through adolescence. Inactive young people are unlikely to become active adults. The challenge is therefore to promote and foster active lifestyles from childhood to adult life. Physical educators are well-placed to meet this challenge but they must reflect on the balance, equity, organization and presentation of their curriculum and extra-curricular programmes. The future health of our children depends upon it.

References

1. Activity and Health Research (1992). Allied Dunbar National Fitness Survey. London, Sports Council and Health Education Authority.

2. Armstrong, N. (1990). Children's physical activity patterns - the implications for physical education. In N. Armstrong (Ed.), New Directions in Physical Education. Champaign, Illinois, Human Kinetics, pp. 1-15.

3. Armstrong, N. (1998). Physical fitness and physical activity during childhood and adolescence. In K.M. Chan and L. Micheli (Eds.), Sports and Children. Hong Kong, Williams and Wilkins, pp. 50-75.

4. Armstrong, N. (1998). Young people's physical activity patterns as assessed by heart rate monitoring. Journal of Sports Sciences, 16 (Suppl):S9-S16.

5. Armstrong, N. and Biddle, S. (1992). Health-related physical activity in the national curriculum. In N. Armstrong (Ed.), New Directions in Physical Education Vol. 2 - Towards a National Curriculum. Champaign, Illinois, Human Kinetics, pp. 71-110.

6. Armstrong, N. and McManus, A. (1994). Children's fitness and physical activity - a challenge for physical education. British Journal of Physical Education, 25:20-6.

7. Armstrong, N. and VanMechelen, W. (1998). How fit and active are children and youth? In S. Biddle, N. Cavill and J. Sallis (Eds.), Young and Active. London, HEA, pp. 69-97.

8. Armstrong, N. and VanMechelen, W., Eds. (2000). Paediatric Exercise Science and Medicine. Oxford, Oxford University Press.

9. Armstrong, N. and Welsman, J.R. (1994). Assessment and interpretation of aerobic fitness in children and adolescents. Exercise and Sport Sciences Reviews, 22:435-76.

10. Armstrong, N. and Welsman, J.R. (1997). Young People and Physical Activity. Oxford, Oxford University Press.

11. Armstrong, N. and Welsman, J.R. (2000). Aerobic fitness. In N. Armstrong and W. Van Mechelen (Eds.), Paediatric Exercise Science and Medicine. Oxford, Oxford University Press, pp. 65-76.

12. Armstrong, N. and Welsman, J.R. (2000). Development of aerobic fitness during childhood and adolescence. Pediatric Exercise Science, 12:128-49.

13. Armstrong, N., Welsman, J.R. and Kirby, B.J. (1998). Peak oxygen uptake and maturation in 12-year-olds. Medicine and Science in Sports and Exercise, 30:165-9.

14. Armstrong, N., Welsman, J.R., Nevill, A.M. and Kirby, B.J. (1999). Modelling growth and maturation changes in peak oxygen uptake in 11-13 year olds. Journal of Applied Physiology, 87:2230-6.

15. Barnett, A., Bacon-Shore, J., Tam, K.H., Leung, M. and Armstrong, N. (1996). The peak oxygen uptake of boys living in a densely populated environment. Annals of Human Biology, 22:525-32.

16. Bell, R.D., Macek, M., Rutenfranz, J. and Saris, W.H.M. (1986). Health indicators and risk factors of cardiovascular diseases during childhood and adolescence. In J. Rutenfranz, R. Mocellin and F. Klimt (Eds.), Children and Exercise XII. Champaign, Illinois, Human Kinetics, pp. 19-27.

17. Central Council for Physical Recreation and National Association of Headteachers (1992). National Survey of Physical Education in Primary Schools. London, CCPR.

18. Durnin, J.V.G.A. (1992). Physical activity levels past and present. In N. Norgan (Ed.), Physical Activity and Health. University Press, Cambridge, pp. 20-27.

19. Gentle, P.H., Caves, R., Armstrong, N., Balding, J. and Kirby, B. (1994). High and low exercisers among 14 and 15 year old British children. Journal of Public Health Medicine, 16:186-94.

20. Glenmark, B., Healberg, G. and Jansson, E. (1994). Prediction of physical activity level in adulthood by physical characteristics, physical performance and physical activity in adolescence: an 11-year follow-up study. European Journal of Applied Physiology, 69:530-8.

21. Klausen, K., Rasmussen, B. and Schibye, B. (1985). Evaluation of the physical activity of school children during a physical education lesson. In J. Rutenfranz, R. Mocellin and F. Klimt (Eds.), Children and Exercise XII. Champaign Illinois, Human Kinetics, pp. 93-101.

22. Kuh, D.J.L. and Cooper, C. (1992). Physical activity at 36 years: patterns and childhood predictors in a longitudinal study. Journal of Epidemiology and Community Health, 46:114-9.

23. Luke, M.D. and Sinclair, G.D. (1991). Gender differences in adolescents' attitudes toward school physical education. Journal of Teaching in Physical Education, 11:31-46.

24. McKenzie, T.L., Feldman, H., Woods, S.E., Romero, K.A., Dahlstrom, V., Stone, E.J., Strikmiller, P.K., Williston, J.M. and Harsha, D.W. (1995). Children's activity levels and lesson content during third-grade physical education. Research Quarterly for Exercise and Sport, 66:184-93.

25. McManus, A. and Armstrong, N. (1997). The physical activity patterns of boys and girls. In D.J. McFarlane (Ed.), Gender Issues in Sport and Exercise. Hong Kong, University Press, pp. 36-39.

26. Mota, J. (1994). Children's physical education activity,assessed by telemetry. Journal of Human Movement Studies, 27:245-50.

27. NIH Consensus Development Panel on Physical Activity and Cardiovascular Health (1996). Physical activity and cardiovascular health. Journal of the American Medical Association, 276:241-6.

28. Raitakari, O.T., Porkka, K.V.K., Taimelo, S., Telema, R., Rasenen, L. and Viikari, J.S.A. (1994). Effects of persistent physical activity and inactivity on coronary risk factors in children and young adults. American Journal of Epidemiology, 140:195-205.

29. Robinson, S. (1938). Experimental studies of physical fitness in relation to age. Arbeitsphysiologie, 10:251-323.

30. Sallis, J.F. and Patrick, K. (1994). Physical activity guidelines for adolescents: A consensus statement. Pediatric Exercise Science, 6:302-14.

31. Sleap, M. (1990). Promoting health in primary school physical education. In N. Armstrong (Ed.), New Directions in Physical Education. Champaign, Illinois, Human Kinetics, pp. 17-36.

32. Sleap, M. and Warburton, P. (1992). Physical activity levels of 5-11 year old children in England determined by continuous observation. Research Quarterly for Exercise and Sport, 63:238-45.

33. Sports Council (1995). Young People and Sport:National Survey Selected Findings. London, Sports Council.

34. Telema, R. and Silvennoinen, M. (1979). Structure and development of 11- to 19-year-olds' motivation for physical activity. Scandinavian Journal of Sports Science, 1:23-31.

35. Thomas, J.R. and Thomas, K.T. (1988). Development of gender differences in physical activity. Quest, 40:219-29.

36. US Department of Health and Human Services (1996). Physical Activity and Health: A Report of the Surgeon General. Atlanta, GA, US Department of Health and Human Services, Centres for Disease Control and Prevention, National Centre for Chronic Disease Prevention and Health Promotion.

37. Welsman, J.R., Armstrong, N., Kirby, B.J., Nevill, A.M. and Winter, E.M. (1996). Scaling peak 2 for differences in body size. Medicine and Science in Sports and Exercise, 28:259-65.

Note: this paper was initially presented to the International Conference in Physical Education and Sport Science, Hong Kong, 2000.