Accelerometer cut-points and youth physical activity prevalence

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EUROPEAN PHYSICAL EDUCATION REVIEW [DOI: 10.1177/1356336X07081795]
Volume13(3):287–299:081795
EPER
Accelerometer cut-points and youth physical
activity prevalence
Jorge Mota, Mónica Valente, Luísa Aires, Pedro Silva, Maria
Paula Santos and José Carlos Ribeiro Research Centre in Physical
Activity Health and Leisure, Faculty of Sport Sciences, University of Porto
Abstract
The purpose of this study was twofold: first, to examine the effects of specific cutoff
scoring points (on the estimated prevalence of meeting health-related guidelines
for physical activity in youth) and, second, to document the differences in gender
physical activity patterns according to two different cut-off points. The sample
comprised 62 children (boys n = 23; girls n = 39) aged 8–16 years old. Children
wore accelerometers for three consecutive weekdays. The daily time spent in
moderate-to-vigorous physical activity (MVPA) was calculated using an equation
regression developed for youth according to different cut-points. The data analysis
from Freedson’s cut points showed that both sexes engaged in significantly (p ≤ .01)
more MVPA when compared with Puyau’s cut points. Boys engaged in significantly
(p ≤ .01) more MVPA activities than girls regardless of the cut-off point used. Our
data also showed that the percentage of students that reach the physical
activity/health related guidelines was significantly higher in both boys (77.3 vs 6.9
percent; p < .001) and girls (60 vs 2.3 percent; p < .001) when Freedson’s cut-off
point was used. Our data showed that for preventive strategies youth specific cutoff
points still need to be refined and, as a result, health-related criteria for young
people need to be based on further research evidence.
Key-words: accelerometer • health-related criteria • physical activity • youth
Introduction
PROOF ONLY
Physical inactivity is associated with increased risk of several chronic diseases
(Raitakari et al., 1997). In adults, it was observed that each 1-MET increase in exercise
capacity conferred a 12 percent improvement in survival (Myers et al., 2002). It has
been suggested that inactivity during youth is linked to several health-related risks
in adulthood (Powell and Dysinger, 1987; Twisk et al., 1997). As researchers begin
to explore the physical activity (PA) dose-response relationship with health
parameters (Bouchard, 2001), it is increasingly important to provide a more precise
estimate of both the quantity and quality of physical activity (Sallis and Saelens,
Copyright © 2007 North West Counties Physical Education Association and SAGE Publications (Los Angeles, London, New Delhi and Singapore)
www.sagepublications.com

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2000). Precise measures of habitual physical activity are necessary in studies designed
to: (1) document the frequency and distribution of physical activity in defined
population groups, (2) determine the amount or dose of physical activity required to
influence specific health parameters (Trost et al., 2000).
However, the assessment of PA in childhood and adolescence is a complex task,
hampered by methodological difficulties in which quality measures play a critical role
(Anderson et al., 2005; Freedson et al., 1998). Wide ranges of methods have been
used to quantify youth PA behaviour. These methods include subjective measures
such as child and parent self-reports and objective measures such as direct observation,
heart rate monitoring, motion sensors and doubly labelled water. The
advantages and disadvantages of different measures have been extensively reviewed
(Sallis and Owen, 1999).
Objective measures with real time data storage capabilities offer a distinct advantage
over self-report methods in that they provide reliable information on patterns of
physical activity within a given day or over several days (Trost et al., 2000). Activity
monitors like Tritrac and MTI Actigraph accelerometer seem to be one solution to
this problem (Freedson and Miller, 2000). The MTI has been shown to be highly
significantly correlated with energy expenditure, as assessed by indirect calorimetry,
and has a high degree of inter-instrument reliability (Ekelund et al., 2001). The
validity studies for the instruments have been conducted in laboratory and field
settings (Brage et al., 2003; Coe and Pivarnick, 2001). Since children are likely to
engage in activities that involve bending, jumping, running and throwing as part of
their daily physical activity, measurement tools should be validated for use with such
activities (Ott et al., 2000 ). Studies carried out with those activities found moderate
and significant correlations, and the researchers concluded that accelerometers are an
appropriate instrument for measuring children’s free-play physical activity (Puyau
et al., 2002).
General guidelines are widely used to describe the amount of physical activity
related to health benefits in youth and are described elsewhere (Cavill et al., 2001;
Corbin and Pangrazi, 1998). Estimates of adherence to published recommendations
for PA depend on estimates of time spent engaging in moderate-to-vigorous physical
activity (MVPA). Since policy and programme strategies are based on prevalence
estimates for meeting these guidelines, it is essential that prevalence estimates are
accurate (Sarkin et al., 2000). Nonetheless, prevalence rates are dependent on the
instrument used to assess PA (Sarkin et al., 2000). For example, it was reported that
for children the extent of sex and ethnic differences in children’s PA depends on the
measure used (Sallis et al., 1998). Riddoch and Boreham (Anderson et al., 2005)
raised this point, commenting that different conclusions had been reached depending
upon the criterion selected to distinguish activity from inactivity. Indeed, several
age-specific activity thresholds have been suggested for youth with different
accelerometer cut points proposed (Freedson et al., 1998; Puyau et al., 2002). This
problem raised questions about the difference in the prevalence estimates of PA.
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MOTA ET AL.: ACCELEROMETER CUT-POINTS AND YOUTH PHYSICAL ACTIVITY 289
However so far, to the best of our knowledge, no studies have attempted to
compare the prevalence rates of health-related physical activity criteria in youth.
Therefore, the purpose of this study was twofold: (1) to analyse the magnitude of
differences in the prevalence estimates of accomplishment of youth PA guidelines
(≥ 60 min/day MVPA) using two age-adjusted MTI cut-points values; and (2) to
document the gender differences in PA according to different two different cut-point
systems.
Methodology
Sample
The participants for this study were a subsample from a longitudinal study to assess
the cardiovascular risk factors in a Portuguese paediatric population. More detailed
information is described elsewhere (Duarte et al., 2000). Data were collected from 84
volunteer students recruited from local schools (Porto region). Of the total sample of
84 students, 22 were excluded from the analysis due to incomplete MTI data. The
sample for the present study comprised of 62 children (boys n= 23 and girls n= 39),
aged 8 to 15 years old. Study procedures were approved by the Portuguese Ministry
for Science and Technology. Informed written consent was obtained from the
children’s parents and individual school principals.
Anthropometric measures and body composition
Stature was measured using the Harpenden Portable Stadiometer (Holtain Ltd, UK).
The values of stature were recorded in centimetres to the nearest mm. Body mass was
measured to the nearest 0.1 kg with an electronic weighing scale (Tanita Inner Scan
BC 532, UK), with the subjects in T-shirt and shorts. Body mass index (BMI) (kg/m 2 )
was calculated from the ratio of weight /height 2 .
Daily physical activity
The MTI model 7164 accelerometer (Manufacturing Technology Incorporated, Fort
Walton Beach, FL) was used as an objective measure of daily physical activity. The
MTI (formerly known as the CSA) uniaxial accelerometer is a small, lightweight
single-channel accelerometer designed to measure and record acceleration ranging in
magnitude from 0.05 to 2.00 G with frequency response from 0.25 to 2.50 Hz. The
filtered acceleration signal is digitized and the magnitude is summed over a userspecified
period of time (an epoch interval). At the end of each epoch, the summed
value is stored in memory and the numerical integrator is reset. This process can
repeat itself for 22 consecutive days, if a one-minute epoch is used, before the memory
is filled. With a reader interface unit (RIU) connected to a computer, it is possible to
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290 EUROPEAN PHYSICAL EDUCATION REVIEW 13(3)
download the recorded data and use the software supplied with the RIU to
analyse it.
Protocol and MTI data reduction
Each student in the present study was scheduled to wear the MTI for three consecutive
school weekdays (Tuesday to Thursday) between April and May 2004. For
the present study, the epoch duration or sampling period was set at 1 minute and
output was expressed as counts per minute (cnts.min –1 ). The accelerometer was placed
in a small nylon pouch and firmly adjusted at the child’s right hip by an elastic waist
belt. A data sheet was given to each child who was instructed to record the time when
the monitor was attached in the morning and detached in the evening and every time
he/she performed any restricted activities like showering and swimming. The
programme excludes from analysis MTI output equal to zero for more than 20
continuous minutes, assuming that the device is not being worn during these periods.
Subjects were included in the analysis only if they had three complete days of
MTI data which included at least 12 hours of recorded time for each day.
Statistical analysis
Analysis was carried-out with SPSS (Windows version 11.0). Descriptive statistics
were used in order to characterize and describe the sample. The age-specific count
ranges developed by Freedson et al. (1997) [Fcut-point] and Puyau et al. (2002)
[Pcut-point] were used to determine the number of minutes of MVPA. For the
analysis, only MVPA was considered since youth health-related physical activity
guidelines stressed the health-related participation in MVPA (Cavill et al., 2001).
Thus the daily time spent in MVPA (≥ 3 MET) was calculated by summing the
minutes of moderate, vigorous, and very vigorous minutes for each day.
Intra-class correlations coefficients (ICC) were used to assess the stability of the
accelerometer scores across the three days of assessment, which estimates the
reliability of a single day’s measure. Spearman rank order correlations were used to
compare the average number of MVPA minutes over three days obtained from the
two cut-off point methods. Gender differences for total time spent in MVPA were
analysed by independent t-test. For testing the significance of differences among boys
and girls, the chi-squared was applied to determine differences between frequencies
of participation in MVPA. The level of significance was set at p < 0.05.
PROOF ONLY
Results
Subject descriptive characteristics and MTI raw data per day are summarized by
gender in Table 1. No significant gender differences were found for age and physical
characteristics of the sample. The average daily hours of assessment were about 14.
Results are consistent with the expected sleeping habits of children and adolescents

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MOTA ET AL.: ACCELEROMETER CUT-POINTS AND YOUTH PHYSICAL ACTIVITY 291
Table 1
Descriptive characteristics of the sample (mean ± SD)
Boys (n = 23) Girls (n = 39) p
X ±SD
X ±SD
Age 11.1 ± 2.82 12.4 ± 2.6 .092
Body mass (kg) 42.5 ± 13.3 44.5 ± 12.6 .820
Height (cm) 147.9 ± 15.1 149.9 ± 13.5 .571
BMI (kg/m 2 ) 20.3 ± 3.5 19.4 ± 3.2 .281
Time (h/day) 14.1 ± 1.1 14.2 ± 1.1 .930
MTI (counts. min –1 ) 596.32 ± 220.20 498.96 ± 160.08 .01
which have been described in a similar population (Mota et al., 2003). The total
amount of PA expressed as total counts (cnts.min –1 ) by the MTI were significantly
higher in boys than girls.
The reliability of MTI scores across days (Table 2) provides an estimate of
variability of PA. The intra-class correlations coefficients (ICC) estimated for a single
day for MTI scores ranged between 0.30 and 0.60 for total counts. ICC for moderate
intensities either in boys (0.70–0.78) or girls (0.60–073) was higher in Fcut-points
than for Pcut-points (0.31–0.49 in boys and 0.17–0.41 in girls). The ICC for MVPA
was higher, regardless of gender, in Fcut-points (0.69–0.72 in boys and 0.58–0.70 in
girls) compared to Pcut-points (0.35–0.53 in boys and 0.42–0.66 in girls).
Spearman correlation coefficient and Intra-class correlation coefficient between
MVPA from MTI accelerometer cut-points is shown in Table 3. Both, ICC (0.33;
p < 0.05) and Spearman’s correlation (R = 0.57; p = .005) were statistically significant
in boys but not in girls.
Table 4 shows the time spent per day (min.) in MVPA according to the two cutoff
points by gender. As expected, the MVPA mean number in minutes is different
according to the cut-point used. Total MVPA (min) was significantly higher when
using the Fcut-point (149 and 111 min.d –1 ) compared to the Pcut-point (35 and
27 min.d –1 ). Boys engaged in significantly (p ≤ .01) more MVPA than girls if the
Fcut-point was used, while no statistical significance was found for the Pcut-point.
The prevalence estimates of accomplishment of youth PA guidelines (≥ 60
min/day MVPA) using the two age-adjusted MTI cut-points methods are shown in
Figure 1. The results showed that the percentage of students that reach the physical
activity-health related criteria was significantly higher in both boys (95.7% vs 17.4%,
p < .000) and girls (87.2% vs 5.1%, p < .000) when the Fcut-point was used instead
the Pcut-point.
PROOF ONLY
Discussion
The aim of this study was to analyse the magnitude of differences in the prevalence
estimates of accomplishment of youth PA guidelines (≥ 60 min/day MVPA) using
two age-adjusted MTI cut-points values. It might seem intuitive that using different

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292 EUROPEAN PHYSICAL EDUCATION REVIEW 13(3)
Table 2 The reliability (intra-class correlations coefficients, ICC) of MTI scores across days
Activity BOYS GIRLS
Total Counts ICC (CI 95%) ICC (CI 95%)
Day 1 vs Day 2 0.48 (0.09–074) *** 0.35 (0.04–0.59) ***
Day 1 vs Day 3 0.60 (0.26–0.81) *** 0.40 (0.1–0.63) ***
Day 2 vs Day 3 0.52 (0.14–0.76) *** 0.30 (0.02–0.55) ***
Fcut-point Pcut-point Fcut-point Pcut-point
Moderate ICC (CI 95%) ICC (CI 95%) ICC (CI 95%) ICC (CI 95%)
Day 1 vs Day 2 0.78 (0.39–0.86) *** 0.36 (0.03–0.67)* 0.60 (0.35–0.77) *** 0.41 (0.11–0.64) **
Day 1 vs Day 3 0.70 (0.41–0.86) *** 0.49 (0.10–0.74)** 0.73 (0.54–0.85) *** 0.26 (0.01–0.53)
Day 2 vs Day 3 0.71 (0.43–0.87) *** 0.31 (0.03–0.63) 0.69 (0.47–0.82) *** 0.17 (–0.15–0.46)
Vigorous
Day 1 vs Day 2 0.48 (0.09–0.74) ** –0.01 (–0.41–0.40) 0.43 (0.14–0.66) *** 0.10 (–0.22–0.40)
Day 1 vs Day 3 0.50 (0.13–0.76) ** 0.32 (–0.10–0.64) 0.48 (0.15–0.66) ** 0.46 (0.17–0.67) **
Day 2 vs Day 3 0.57 (0.21–0.79) ** 0.37 (–0.04–0.67)* 0.42 (0.13–0.65) ** 0.10 (–0.22–0.40)
MVPA
Day 1 vs Day 2 0.72 (0.45–0.87) *** 0.35 (–0.07–0.66)* 0.18 (0.33–0.76) *** 0.42 (0.12–0.65) **
Day 1 vs Day 3 0.70 (0.41–0.86)*** 0.72 (0.45–0.87)*** 0.70 (0.50–0.83) *** 0.66 (0.44–0.81) ***
Day 2 vs Day 3 0.69 (0.40–0.86)*** 0.53 (0.15–0.77) * 0.64 (0.41–0.80) *** 0.66 (0.43–0.80) ***
PROOF ONLY
* p < .05; ** p < .01; *** p < .001.

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MOTA ET AL.: ACCELEROMETER CUT-POINTS AND YOUTH PHYSICAL ACTIVITY 293
Table 3 Spearman correlation (Rho) and Intra-class correlation coefficient (ICC)
between MVPA from MTI accelerometer cut-points
MTI DATA
ICC (CI-95%) p Rho p
Boys 0.33 (0.08–0.65) .05 0.57 .005
Girls 0.16 (–0.15–0.45) ns 0.30 ns
Table 4 Time spent per day (min.) in moderate, vigorous and MVPA according to the
two cut-off points by gender
Boys Girls p
X ±SD CV X ±SD CV
Freedson et al. (1997)
MVPA (min. d –1 ) 149.0 ± 72.6 48.6 111.4 ± 56.9 51.1 .01
Moderate (min. d –1 ) 129.8 ± 60.9 46.9 100.1 ± 49.2 49.2 .01
Vigorous (min. d –1 ) 19.1 ± 14.3 74.8 11.3 ± 9.4 83.1 .01
Puyau et al. (2002)
MVPA (min. d –1 35.2 ± 24.5 69.6 27.8 ± 17.1 61.5 ns
Moderate (min. d –1 ) 34.4 ± 23.7 68.9 27.2 ± 16.3 59.9 ns
Vigorous (min. d –1 ) 0.8 ± 1.3 162.5 0.6 ± 1.2 200 ns
(%) 100
80
60
40
20
*
PROOF ONLY
*
*
0
Boys
Girls
Physical Activity
**
Note.* p < 0.001 – differences between gender.
Figure 1 Percentage of children that accomplished the youth physical activity
guidelines (60 minutes/day of MVPA) according to different cut-off points

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294 EUROPEAN PHYSICAL EDUCATION REVIEW 13(3)
cut-points would lead to different estimates of PA prevalence, but to the best of our
knowledge this is one of the first studies showing differences in PA level between two
well-known cut-points used in young people MTI analysis.
Published accelerometer youth-related cut-off levels corresponding to MVPA
intensity levels were used in this study (Freedson et al., 1997; Puyau et al., 2002).
Both proposed cut points are age-specific, which is needed since the correspondence
between counts and energy expenditure at different workloads is likely to differ
between age-groups (Schofield, 1985). Nevertheless, the critical point is that different
cut-points influence the prevalence of MVPA among young people. To what
extent youth meet the recommended guidelines is a timely issue with a public health
interest, because there is a risk of misinterpretation depending on cut-points used.
The analysis showed that using Fcut-points both sexes engaged in significantly
(p ≤ .01) more MVPA compared with Pcut-points. Further, boys engaged in significantly
more MVPA than girls (p ≤ 0.01) when Fcut-point is considered. Comparisons
of minutes of activity per day between the two cut-off points clearly showed that the
Pcut-point estimate significantly less minutes of MVPA activity level (p ≤ .001) than
the Fcut-point. Total MVPA was 149.0 vs 111.4 min.d –1 for Fcut-point, and 35.2 vs
27.8 min.d –1 for Pcut-point, respectively for boys and girls. The findings of the
present study agree with another survey using the two methods to validate an
adolescent diary. In that study the sample was less active than in the present study.
Total MVPA was 86.5 vs 46.9 min.d –1 for MTI Fcut-point, and 27.1 vs 9.2 min.d –1
for Pcut-point, respectively for boys and girls. The mean values of MVPA within
Fcut-point are in accordance with other studies that have used objective measures of
physical activity, which reported significantly higher levels of physical activity in boys
than girls (Pate et al., 2002; Santos et al., 2003; Trost et al., 2002).
Our data also showed that the percentage of students that reach the physical
activity-health related criteria (at least 60 min of MVPA/day) was significantly higher
in both boys (95.7% vs 17.4%; p < .001) and girls (87.2% vs 5.1%, p < .001) when
the Fcut-point was used compared to Pcut-point. Thus, when data were reported to
Fcut-point it appears that children meet minimum physical activity recommendations
for health, which agrees with other studies (Hussey et al., 2001; Sleap and
Tolfrey, 2001). The differences in estimates of the mean number of minutes engaged
in MVPA are important from a public health perspective when defining estimates and prevalence
of levels of health-related PA achievements. However those differences are difficult to
explain. One can argue that a possible explanation lies in the fact that Fcut-point
tends to give higher prevalence estimates, probably because cut-offs are derived from
a laboratory setting, while Pcut-point was originated in daily routine activities with
target on sedentary activities rather than MVPA, which may lead to a under-estimation
of moderate activities. As reported for adults, the high cut-off points lead to a misclassification
of some moderate physical activities (Ainsworth et al., 2000). In fact, a
study carried out with the aim to evaluate the validity of a questionnaire against the
two cut-points methods, showed that the best agreement was with Fcut-point for
students whose average total MVPA < 60 min. (Anderson et al., 2005). Additionally,
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MOTA ET AL.: ACCELEROMETER CUT-POINTS AND YOUTH PHYSICAL ACTIVITY 295
it might be considered that some differences in estimation of vigorous activities may
relate to the epoch time (sampling interval) procedures. The 1 minute epoch was used
in this study. Moreover the 5 seconds epoch has been shown as the best approach to
detect vigorous PA in youth (Nilsson et al., 2002). Nevertheless, in the present study
the reliability values of the MTI scores across the day were similar to other findings
reported in the literature (Mota et al., 2002; Sallis et al., 1993; Trost et al., 2000). In
children from grades 1 to 6, the single-day reliability of MVPA assessed by MTI
ranged from 0.46 to 0.49 while the values decreased as children got older, ranging
from 0.32 to 0.31 (Trost et al., 2000). The scores obtained may also be representative
of subjects’ day-to-day variability in MVPA participation.
Our data showed high CV values for boys and girls in vigorous activities with
those related to Pcut-point over 100 percent (Table1). This issue should also be
considered along with gender. Indeed, our results showed statistically significant
differences between boys and girls for Fcut-point but not for Pcut-point, which might
suggest different accuracy and sensitivity of cut-points according to gender. Further,
the correlations (ICC and Spearman’s correlation) between MVPA MTI cut-points
were statistically significant in boys but not in girls, which may be a reflection of the
restricted range of MVPA among girls.
Limitations to the present study should be recognized. The sample is small and
it is believed that a larger group of participants is needed to clarify to what extent
the differences are significant for public health strategies. Further studies should be
designed to improve such estimations since the validity of activity monitors vary by
setting (laboratory or field) and type of activity (Welk et al., 2000).
Conclusion
The data clearly show that compliance with a specific PA guideline will depend on
the cut-points used to interpret the data collected. Therefore, the cut-points still need
to be refined, and as a result health-related criteria for young people need to be based
on further research evidence.
Acknowledgment
PROOF ONLY
This study was supported in part by grant FCT: PSAU/122/96 and PAFID 284/2005.
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Résumé
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Seuil d’activation et fréquence d’Activité Physique chez les
jeunes
Le but de cette étude était double : tout d’abord, l’examen des effets de seuils spécifiques,
puis, dans un second temps, la documentation des différences des modèles d’activité
physiques liées au genre selon deux seuils différents. L’échantillon était composé de 62 enfants
(garçons n = 23; filles n = 39) âgés de 8 à 16 ans. Les enfants ont porté des
cardiofréquencemètres pendant trois jours consécutifs. Le temps quotidien d’activité
physique modérée à vigoureuse a été calculé en utilisant une régression d’équation
développée spécifiquement pour un jeune public au regard de seuils différents. L’analyse des
données à partir des seuils de Freedson a montré que les deux sexes se sont engagés

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298 EUROPEAN PHYSICAL EDUCATION REVIEW 13(3)
significativement plus (p ≤ 0.01) dans une activité physique modérée à vigoureuse qu’en
comparaison avec les seuils de Puyau. Les garçons se sont engagés significativement plus
(p ≤ 0.01) dans une activité physique modérée à vigoureuse que les filles indépendamment
du seuil utilisé. Nos données ont également montré que le pourcentage d’élèves qui atteint
le seuil d’une activité de santé en référence aux directives était significativement plus élevé
tant chez les garçons (77.3 % contre 6.9 %; p < 0.001) et que chez les filles (60 % contre
2.3 %; p < 0.001) en recourant au seuil de Freedson. Enfin, sur la base de nos résultats, il
apparaît que, pour une stratégie préventive, les seuils spécifiques à un jeune public devraient
être ré-affinés, et en conséquence les critères concernant la santé pour les jeunes devraient
être basés sur de futurs résultats de recherche.
Resumen
Puntos de corte del acelerómetro y prevalencia de la actividad
física juvenil
El propósito de este estudio es doble. Por un lado se ha pretendido estudiar los efectos de
la puntuación límite específica (sobre la prevalencia estimada de cumplir las directrices
sanitarias sobre la actividad física en la juventud), y, por otro, se pretendía documentar las
diferencias existentes en los modelos de actividad física según el sexo de acuerdo con dos
puntos de corte diferentes. La muestra se realizó sobre 62 menores (23 niños y 39 niñas)
de entre 8 y 16 años de edad. Los menores llevaron puesto un acelerómetro durante tres
días laborables consecutivos. El tiempo que diariamente dedicaron a una actividad física entre
moderada y vigorosa (AFMV) se calculó utilizando una ecuación de regresión desarrollada
para los jóvenes según diferentes puntos de corte. El análisis de los datos a partir de los
puntos de corte establecidos por Freedson ha demostrado que ambos sexos realizan
bastante más AFMV (p ≤ 0,01) en comparación con los puntos de corte de Puyau. Los niños
realizan bastante más AFMV (p ≤ 0,01) que las niñas, independientemente de los puntos de
corte utilizados. Los datos que obtuvimos también indican que el porcentaje de estudiantes
que cumplen las directrices sanitarias sobre actividad física fue bastante mayor tanto en el
caso de los niños (77,3% frente al 6,9%; p < 0,001) como en el de las niñas (60% frente al
2,3%; p < 0,001) cuando se utilizaban los puntos de corte de Freedson. Nuestros resultados
demuestran que los puntos de corte específicos para la juventud, en lo que se refiere a las
estrategias preventivas, necesitan una reformulación, y, en consecuencia, los criterios sanitarios
para los jóvenes deben basarse en los resultados de futuras investigaciones.
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Zusammenfassung
Messpunktvorgaben von Beschleunigungsmessern und
Häufigkeit körperlicher Aktivität bei Jugendlichen
Der Zweck dieser Studie war ein zweifacher. Zuerst galt es die Auswirkung spezifischer
Grenzwertvorgaben (bezüglich der Einschätzung, mit gesundheitsbezogenen Richtlinien für

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MOTA ET AL.: ACCELEROMETER CUT-POINTS AND YOUTH PHYSICAL ACTIVITY 299
körperliche Aktivitäten im Jugendalter übereinzustimmen) zu untersuchen, und zweitens
sollten die Unterschiede in geschlechterspezifischen Mustern körperlicher Aktivität
entsprechend zwei verschiedenen Grenzwertvorgaben dokumentiert werden.. Die
Stichprobe umfasste 62 Kinder (Jungen n = 23; Mädchen n = 39) im Alter von 8–16 Jahren.
Die Kinder trugen an drei aufeinander folgenden Wochentagen Beschleunigungsmesser.
Die Zeit, die sie täglich für moderate bis starke körperliche Aktivität (moderate-to-vigorous
physical activity (MVPA) aufwendeten wurde mittels einer Regressionsgleichung berechnet,
die für Jugendliche entsprechend den unterschiedlichen Messpunktvorgaben entwickelt
worden war. Die Datenauswertung nach Freedsons Schwellenwerten zeigten für beide
Geschlechter signifikant mehr MVPA (p ≤ 0.01), mehr MVPA im Vergleich mit Puyaus
Schwellenangaben. Unabhängig von den verwendeten Schwellenwertvorgaben beteiligten
sich Jungen signifikant (p ≤ 0.01) mehr an MVPA Aktivitäten (Sic!) als Mädchen. Unsere Daten
zeigten auch, dass der Prozentsatz der Schüler, die die Vorgaben der gesundheitsbezogenen
Richtlinien für körperliche Aktivität erfüllten, sowohl bei Jungen (77.3% vs 6.9%; p < 0.001)
als auch Mädchen (60% vs. 2.3%; p < 0.001) signifikant höher war, wenn Freedsons
Schwellenwert benutzt wurde. Unsere Daten zeigten auch, dass es nötig ist, für
Präventivmassnahmen jugendspezifische Messwertvorgaben noch feiner einzustellen. Weiters
müssen gesundheitsbezogene Kriterien für Jugendliche auf weiteren wissenschaftlichen
Erkenntnissen aufgebaut werden.
Jorge Mota, Mónica Valente, Luísa Aires, Pedro Silva, Maria Paula Santos and
José Carlos Ribeiro are based at the Research Centre in Physical Activity Health and
Leisure, Faculty of Sport Sciences, University of Porto.
Address for correspondence: Jorge Mota, FCDEF-UP, R.Plácido Costa, 91 4200 450,
Porto, Portugal. [email: jmota@fcdef.up.pt]
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