European Journal of Clinical Nutrition (1999) 53, 840±843
ß 1999 Stockton Press. All rights reserved 0954±3007/99 $15.00
http://www.stockton-press.co.uk/ejcn
Physical activity levels in a sample of Oxford school children
aged 10 ± 13 years
CJK Henry1*, JD Webster-Gandy1 and M Elia2
1
School of Biological and Molecular Sciences, Oxford Brookes University, Gipsy Lane, Oxford UK and 2Dunn Clinical Nutrition Centre,
Hills Road, Cambridge CB2 2DH, UK
Objective: To determine physical activity levels (PAL) in children aged between 10 and 13 y.
Design: Cross-sectional study of physical activity levels on school days, with and without physical education
(PE) lessons and at weekend. Data were collected using self-reported activity diaries.
Setting: The children were recruited from a middle school in Oxford. Basal metabolic rate (BMR) and
anthropometry were measured in the school.
Subjects: Thirty-eight children (12 boys and 26 girls), aged 10 ± 13 y, returned completed activity diaries. PAL
values were calculated by applying physical activity ratios (PAR) to the time spent on each activity. BMR and
anthropometry were measured within 20 d of activity diary completion.
Results: The mean s.d. (range) PAL values for all children were 1.52 0.08 (1.34 ± 1.71), 1.50 0.05 (1.44 ±
1.57) for boys and 1.53 0.10 (1.34 ± 1.71) for girls. The lowest PAL value (1.48 0.13, mean s.d.) was
observed in girls on school days without PE lessons. The lowest PAL value in boys (1.46 0.13, mean s.d.)
was observed at the weekend. PE lessons made a signi®cant difference to the PAL values for boys (1.58 0.09)
and girls (1.60 0.12). A wide range of PAL values (1.20 ± 1.87) was recorded in these children. The total
energy expenditure for the boys was slightly lower than the estimated average requirements (EAR) predicted by
the Department of Health (8.71 0.96 MJ compared with 8.86 MJ=d) for this age group. The girls had a higher
average energy expenditure than the predicted EAR (8.47 1.00 MJ=d compared with 7.885).
Conclusions: The children in this study may be classi®ed as light to moderately active with PAL values ranging
from 1.20 to 1.87. The promotion of physical activity in childhood will have bene®cial effects for the child and
their future wellbeing. Programmes aimed at preventing obesity in children should encourage physical activity as
well as promoting appropriate dietary changes.
Sponsorship: NeÂstle Foundation, Lausanne, Switzerland.
Descriptors: PAL values; adolescence; total energy expenditure
Introduction
The World Health Organization (1998) has described
obesity as a global epidemic. The increasing prevalence
of obesity in children and adolescents has received increasing attention. A report by Power et al (1997), based on the
1958 UK birth cohort, found that 17 ± 18% of obese adults,
aged 33 y, were obese as children and that the more obese
the child the greater the likelihood that they will become
obese adults. This appears to be particularly true for obese
adolescents. The prevalence of childhood obesity is high in
all developed countries (World Health Organization, 1998).
The treatment of obesity in adulthood is dif®cult and is
accompanies by a low success rate. An intervention programme that is aimed at the prevention of obesity and the
identi®cation of children at risk of developing obesity early
in life may be a useful and alternative strategy.
Whilst numerous factors have been proposed as favouring weight gain in children, the two most important factors
appear to be an increased consumption of energy dense
food and the reduction in physical activity (or both)
*Correspondence and guarantor: CJK Henry.
Contributions: CJK Henry, study originator and director, interpretation of
data and preparation of the manuscript; JD Webster-Gandy, analysis and
interpretation of data and preparation of the manuscript; M Elia, Co PhD
supervisor of S Dyer; S Dyer, data collection.
Received 28 January 1999; revised 15 April 1999; accepted 7 May 1999
(Prentice & Jebb, 1995). Dietary surveys in the UK suggest
that the increased prevalence of obesity has occurred
despite a decrease in overall fat consumption (Ministry of
Agriculture, Fisheries & Food, 1994). It is therefore likely
that energy expenditure has decreased during this period.
An evaluation of the factors in¯uencing weight gain is not
only of academic interest but also has signi®cant policy
implications.
This study was designed to examine activity levels and
basal metabolic rate (BMR) in a group of school-aged
children and the contribution these make to total daily
energy expenditure.
Subjects and Method
Subjects
Eighty-one Oxford school children aged 10 ± 13 y, initially
volunteered to take part in the study. The children were
recruited by distributing a questionnaire via the teachers at
a middle school in Oxford. Once the children agreed to
participate in the study, the carers and children were invited
to an open meeting to meet the researchers. A full and
detailed explanation of the study objectives and protocol
was presented at this time. After the meeting thirty-eight
children (47%) entered the study and completed the activity
diaries. These diaries formed the basis of our analysis.
Basal metabolic rate and anthropometry was measured in
Physical activity levels in Oxford school children
CJK Henry et al
Table 1 Subject characteristics
Variable
Boys (n ˆ 12)
Mean s.d.
Girls (n ˆ 26)
Mean s.d.
Age (y)
Weight (kg)
Height (cm)
Body mass index (kg=m2)
Fat (kg)
Pubertal stage (mode)
Menarche (n)
11.71 0.81
40.09 7.37
149.00 9.40
17.94 1.92
8.64 3.22
2
±
11.97 0.85
43.86 9.70
150.17 6.92
19.32 3.33
11.81 5.33
2
3
all subjects. The characteristics of the 38 children (12 boys
and 26 girls) are shown in Table 1.
The Oxford Health Authority ethics committee approved
the protocol and informed consent was obtained from the
carers of each child.
Assessment of pubertal stage
Pubertal stage was assessed by two doctors working in
Child Health using Tanners puberty ratings (Tanner, 1978).
A male doctor assessed the appearance of pubic hair and
gonad development in the boys. A female doctor assessed
the girls breast development. In addition, the girls were
asked if menarche had occurred. The classi®cations of
pubertal stage are shown in Table 1.
Activity diaries
Activity diaries, as described by Bouchard et al (1983),
were completed by the children on 3 days of the week.
These were a school day without a physical education (PE)
lesson, a school day with a PE lesson and a day at the
weekend. The inclusion of a day at the weekend was
recommended by Bouchard et al (1983) and Huang &
Malina (1996). Each individual child was given verbal
and written instructions with an example of a completed
diary. During the school day the time slots were designed to
follow the school timetable. One section was available for
each lesson (40 min), break time (20 min) and the lunch
period (50 min). This simpli®ed design was used to
improve subject compliance. Outside school hours and at
the weekend the time was divided into 15-min sections.
The children recorded their activity during each time slot.
exchange data were collected. The ®rst 5 ± 10 min of data
were discarded, as recommended by Isbell et al (1991).
This allowed the subject time to acclimatize to the canopy
and instrument noise. The average of the last 20 min of
measurements was used to determine 24 h BMR. Using the
method described by Rieper et al (1993) the within subject
coef®cient of variation was 2.0%. BMR was measured
within 10 ± 20 d of completion of the activity diaries.
Calculation of total energy expenditure
Using the factorial method (FAO=WHO=UNU, 1985) 24 h
total energy expenditure (TEE) was calculated by multiplying the measured BMR by the PAL and adding the
estimated energy requirement for growth at each age
(Department of Health, 1996).
Anthropometry
Height was measuring using a portable, free-standing
stadiometer (CMS Weighing equipment, London NW1
0JH). The children were measured without shoes according
to the procedure detailed by Gordon et al (1988). Weight
was measured using an electronic balance accurate to 100 g
(Soehnle model 7300, CMS Weighing Equipment, London,
NW1 0JH). The children were weighed in indoor clothing.
All measurements were made in the fasting state. Skinfold
measurements were made at ®ve sites (biceps, triceps,
subscapular, suprailiac, and medial calf). Skinfold measurements were used to derive percent body fat (Parizkova &
Roth, 1972), and fat free mass (FFM).
Statistical analysis
The results were compared within and between groups
using paired and unpaired Student's t-tests, as appropriate.
Results
Activity coding
The recorded activities were translated into physical activity ratios (PAR) using child speci®c PARs (Torun, 1990)
and as multiples of adult PARs (James & Scho®eld, 1990).
Torun (1990) has suggested a multiple of 0.65 for children
aged 6 ± 12.9 y and 0.8 for children 13 ± 15 y. The daily
physical activity level (PAL) was calculated from the PAR
values and the recorded activities as described by Torun et
al (1996).
PAL values
Table 2 shows the calculated PAL values (mean s.d. and
range) in boys and girls. There were no signi®cant differences in the PAL values between the boys and girls on any
of the 3 days surveyed. For the boys the lowest mean PAL
value (1.46) was observed during the weekend, and for the
girls the school day without a PE lesson had the lowest
mean PAL value (1.48). The level of activity at weekends
was higher for the girls than the non-PE lesson school day
(1.52 and 1.48). Compulsory activity at school made a
signi®cant difference (P < 0.05 for boys and for girls) to the
PAL compared with the school day without PE lesson.
The distribution of PAL values for all the children is
shown in Figure 1. Whilst a small proportion of children
were extremely inactive (PAL values of 1.2 ± 1.3) or
extremely active (PAL values greater than 1.8) most fell
in the PAL range of 1.3 ± 1.8.
Measurement of basal metabolic rate
Basal metabolic rate (BMR) was measured by indirect
calorimetry using a ventilated hood system (Datex Deltatrac, Datex Instrumentation Corp. Helsinki, Finland). All
measurements were made in the post-absorptive state, in a
thermoneutral environment (26 ± 28 C) and with no external stimulation while the subjects were awake and supine.
The calorimeter was calibrates with a reference gas mixture
(95% oxygen and 5% carbon dioxide (s.d. 0.003%)) prior to
each session. Approximately 30 min of respiratory gas
BMR and TEE
BMRs are shown in Table 3. The total daily energy
expenditure, based on the factorial method is shown in
Table 3. For boys and girls the lowest daily energy
expenditures occurred on school days without a PE
lesson. TEE was signi®cantly lower (P < 0.05) at weekends, compared to the school day with PE lessons for boys
but not for girls. The highest TEE occurred on school days
with PE lessons for boys and girls, with TEEs of
9.17 1.23 and 8.83 1.13 MJ=d for boys and girls
841
Physical activity levels in Oxford school children
CJK Henry et al
842
Table 2 Physical activity levels (mean s.d.) range
Day
Number
Weekend
School day with PE lesson
School day without PE lesson
Average
Boys
Girls
All children
12
1.46 0.13
(1.30 ± 1.73)
1.58 0.09*
(1.40 ± 1.75)
1.47 ± 0.07d
(1.37 ± 1.60)
1.50 0.05
(1.44 ± 1.57)
26
1.52 0.17
(1.20 ± 1.85)
1.60 0.12*
1.40 ± 1.87)
1.48 0.13***
(1.24 ± 1.72)
1.53 0.10
(1.34 ± 1.71)
38
1.50 0.16
(1.20 ± 1.85)
1.59 0.11**
(1.40 ± 1.87)
1.48 0.12***
(1.24 ± 1.72)
1.52 0.08
(1.34 ± 1.71)
*P < 0.05 when comparing weekend with the school day with PE lesson.
**P < 0.01 when comparing weekend with school day with PE lesson.
d
P < 0.05, ***P < 0.005 when comparing school day with a PE lesson with school day without a PE lesson.
Figure 1 Distribution of physical activity level.
Table 3 Basal metabolic rate and total energy expenditure (MJ=d) (mean
s.d.) range
Basal metabolic rate
Weekend
School day with PE lesson
School day without PE lesson
Average
Department of Health Estimated
Average Requirement
Boys
Girls
5.60 633
(4.70 ± 6.72)
8.44 1.22
(7.34 ± 11.24)
9.17 1.23*
(7.32 ± 10.79)
8.52 0.82**
(7.13 ± 10.03)
8.71 0.96
(7.46 ± 10.57)
8.86
5.34 6.59
(3.67 ± 6.35)
8.39 1.10
(6.37 ± 10.62)
8.83 1.13
(6.04 ± 11.22)
8.21 1.21**
(5.78 ± 10.51)
8.47 1.00
(6.08 ± 9.99)
7.885
*P < 0.05 compared to weekend.
**P < 0.001 compared to school day without a PE lesson.
respectively; this was signi®cantly greater (P < 0.001) than
school days without PE lessons.
The average TEE for the boys was 0.15 MJ=d lower than
the estimated average requirement (EAR) (Department of
Health, 1996), but for the girls the average TEE was
0.585 MJ=d higher than the EAR.
Discussion
Current methods to assess physical activity in children
include the use of heart rate monitors, accelerometers,
activity diaries and doubly labelled water (DLW). Whilst
DLW is considered the `Gold standard' its extensive use is
limited by cost and sample selection bias. Recently Johnson
et al (1998) reported that the Caltrac accelerometer was a
poor predictor of physical activity related energy expenditure in children. This raises the question of which is the
most appropriate method to assess physical activity energy
expenditure in free-living preadolescent children. Activity
diaries have been widely used and have recently been
validated using doubly labelled water (Bratteby et al,
1997). Whilst the accuracy of this method largely depends
on the co-operation of the subjects, Bouchard et al (1983)
have shown that the method is both reliable and reproducible. In its simplest form the activity diary is a logbook
where the subject completes the diary every 15 min covering 1440 min per day. This method, with slight modi®cations, was used in this study. Although the exact
methodology used in this study has not been validated
using DLW, the authors are con®dent that the minor
alterations to the protocol are unlikely to reduce the
methods reliability.
The average PAL values in the present study were 1.50
for boys and 1.53 for girls compared with the Department
of Health (1996) levels of 1.56 and 1.48. Whilst the boys
were less active than the level described by the Department
of Health those of the girls were slightly higher. The girls in
this study were more active than the boys and had an
average PAL value closer to that described by the Department of Health. However, the PAL values displayed a wide
range in both boys and girls. For example one girl had a
weekend PAL of 1.20, a level of energy expenditure merely
20% greater than BMR. Only on school days with PE
lessons did the PAL for boys exceed the values recommended by the Department of Health. The girls' activities
at weekends and on school days with PE lessons are greater
than those quoted by the Department of Health. The results
presented here are in concordance with a study by Armstrong et al (1990) in 11 ± 16 year old British children.
They concluded that (based on heart rate monitoring) the
children studied had `surprisingly low levels of physical
activity'.
Based on the classi®cation of Torun et al (1996) most of
the children in our study may be classi®ed as performing
Physical activity levels in Oxford school children
CJK Henry et al
light physical activity. Physical activity levels in British
children have concerned many researchers and health
professionals, especially as PE lessons, and in particular
competitive sports, are becoming a smaller part of the
school day. Signi®cantly, television, computer games and
sedentary hobbies are becoming increasingly popular pastimes (Dietz & Gortmaker, 1985). Many researchers
including Sleap & Warburton (1996) and Armstrong et al
(1990) have highlighted concern about the amount of
physical activity undertaken by children in the United
Kingdom. This study appears to con®rm the low levels of
physical activity in children especially in boys. The data
presented here highlight the importance of physical education in increasing activity levels in this group of children.
There is increasing evidence to support the view of
tracking of physical activity patterns (Raitakari et al, 1994,
Kuh & Cooper, 1992) and risk of cardiovascular disease
(Dietz, 1998) from childhood through adolescence into
adulthood (Raitakari et al, 1994). It may therefore be
bene®cial if moderate levels of physical activity are nurtured during childhood.
Conclusions
The present study highlights the wide variation in physical
activity levels shown in this sample of school children aged
10 ± 13 y and the signi®cant contribution PE lessons make
to habitual levels of activity. A small proportion of the
children studied has particularly low PAL values. Physical
activity levels are signi®cantly different at the weekend
compared to school days. However, these results must be
viewed with caution in light of the small sample size and
the possible selection bias of the sample.
Acknowledgements ÐThe authors are grateful to the NeÂstle Foundation,
Switzerland, for funding this research. We gratefully acknowledge the cooperation of the Oxford school and children who took part in the study.
References
Armstrong N, Balding J, Gentle P & Kirby B (1990): Patterns of physical
activity among 11 to 16 year old British children. Br. Med. J. 301, 203 ±
205.
Bouchard C, Tremblay A, Leblanc C, Lortie G, Savard R & Therault G
(1983): A method to assess energy expenditure in children and adults.
Am. J. Clin. Nutr. 37, 461 ± 467.
Bratteby L-E, Sandhagen B, Fan H & Samualson G (1977): A 7-day
activity diary for assessment of daily energy expenditure validated by
the doubly labelled water method in adolescents. Eur. J. Clin. Nutr. 51,
585 ± 5391.
Department of Health (1996) Dietary reference values for food energy and
nutrients for the United Kingdom London: HMSO.
Dietz W (1998): Health consequences of obesity in youth: Childhood
predictors of adult disease. Pediatr. 101, 518 ± 525.
Dietz W & Gortmaker S (1985): Do we fatten our children at the television
set? Obesity and television viewing in children and adolescents.
Pediatr. 75, 807 ± 812.
FAO=WHO=UNU (1985): Energy and Protein Requirements. Report of a
joint FAO=WHO=UNU Expert Consultation. Geneva: World Health
Organization.
Gordon C, Chumlea W & Roche A (1988): Stature, recumbent length and
weight. Anthropometric Standardisation Reference Manual, eds T
Lohman, A Roche & R Martorelli: pp. 1 ± 3. Champaign, Illinois:
Human Kinetics Books.
Huang Y-C & Malina R (1996): Physical activity and correlates of
estimated energy expenditure in Taiwanese adolescents aged 12 ± 14
years of age. A. J. Hum. Biol. 8, 225 ± 236.
Isbell T, Klesges R, Meyers A & Kleges L Measurement reliability and
reactivity using repeated measurements of resting energy expenditure
with a face mask, mouthpiece, and ventilated canopy. J. Parent. Ent.
Nutr. 15, 165 ± 168.
James W & Scho®eld E (1990); Human energy requirements. A
manual for planners and nutritionists. New York: Oxford University
Press.
Johnson RK, Russ J & Goran MI (1998): Physical activity related energy
expenditure in children by doubly labelled water as compared with the
Caltrac accelerometer. Int. J. Obes. 22, 1046 ± 1052.
Kuh & Cooper C (1992): Physical activity at 36 years: patterns and
childhood predictors in a longitudinal study. J. Epid. Comm. Health 46,
114 ± 119.
Ministry of Agriculture, Fisheries & Food (1994) Household food consumption and expenditure. London: Ministry of Agriculture Fisheries
and Food.
Parizkova J & Roth Z (1972): The assessment of depot fat in children from
skinfold thickness measurements by Holtain (Tanner=Whitehouse)
callipers. Hum. Biol. 44, 613 ± 620.
Power C, Lake J & Cole T (1997): Body mass index and height from
childhood to adulthood in the 1958 British birth cohort. Am. J. Clin.
Nutr. 66, 1094 ± 1101.
Prentice A & Jebb S (1995): Obesity in Britain: gluttony or sloth? Br. Med.
J. 311, 437 ± 439.
Raitakari O, Porkka K, Taimelo S, Telema R, Rasenen L & VIIkari J
(1994): Effects of persistent physical activity and inactivity on
coronary risk factors in children and young adults. Am. J. Epid. 140,
195 ± 205.
Rieper R, Karst H, Noack R & Johnsen D (1993): Intra- and interindividual variations in energy expenditure of 14year-old schoolgirls
as determined by indirect calorimetry. Brit. J. Nutr. 69, 29 ± 36.
Sleap M & Warburton P (1996): Physical activity levels of 5-11 year old
children in England: Cumulative evidence from three direct observation
studies. Int. J. Sports Med. 17, 248 ± 253.
Tanner JM (1978): Foetus into Man ± Physical growth from conception
to maturity. London Open Books Publishing Ltd=Fletcher & Son
Ltd.
Torun (1990): Energy cost of various physical activities in healthy
children. Activity, energy expenditure and energy requirements of
infants and children in Cambridge, Massachusetts, USA, B Schurch
and N Scrimshaw (eds) Massachusetts, USA: International Dietary
Energy Consultancy Group.
Torun B, Davies P, Livingstone M, Paolisso M, Sakett R & Spurr G
(1996): Energy requirements and dietary energy recommendations for
children and adolescents 1 to 18 years old. Eur. J. Clin. Nutr. 50,
S37 ± S81.
World Health Organization (1998): Obesity: Preventing and managing the
global epidemic Geneva: WHO.
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