Pensar en Movimiento:
Revista de Ciencias del Ejercicio y la Salud
ISSN  1659-4436
Vol. 11, No.1, pp. 1- 12

Amaury J. Álvarez, MExSc^1(B,C,E),Farah A. Ramírez Marrero, PhD, MSc, CSCS, FASCM^1(A,B,D,F), Alexis Ortiz, PT, PhD, SCS, CSCS^1(B,D) y Lucía del Rosario Martínez PhD, CSCS, NSCA-CPT^1(B,E)
farah.ramirez1@upr.edu
¹Universidad de Puerto Rico
Puerto Rico

Manuscrito recibido: 14/06/2012; aceptado: 01/03/2013; publicado: 15/05/2013

ABSTRACT

Álvarez, A.J., Ramírez Marrero, F.A., Ortiz, A. y Martínez L.R. (2013).Levels of Physical Activity in Puerto Rican Female Adolescents: a pilot study. Pensar en Movimiento: Revista de Ciencias del Ejercicio y la Salud, 11 (1), 1-12. Physical activity (PA) is known to decline and obesity to increase from childhood to adulthood. During adolescence, girls are particularly vulnerable to both physical inactivity and overweight leading to obesity. Childhood and adolescent obesity is a known health problem in Puerto Rico; however, PA has not been well described in this population. The purpose of this study was to evaluate PA levels and factors influencing PA in a group of Puerto Rican adolescent females. Forty participants wore an accelerometer during six consecutive days and completed a PA questionnaire. Participants were divided in two groups according to age (11-13 and 14-16 years). Parents completed a socio-demographic and PA questionnaire. ANOVA and independent t-tests were used to identify differences in moderate to vigorous PA (MVPA) by age group, and between adolescents and their parents. Multiple regression analysis was performed to identify factors related to PA. MVPA averaged 87 (54) min/week with no differences between age groups:11-13y.o. =87 (58) and 14-16 y.o.= 86(50) min/week (p = .95).A significant association was observed between parents and adolescents’ MVPA (r= 0.67, p< .01 The most powerful predictors of the adolescents’ MVPA were parental MVPA and the days parents shared PA with their daughters. Puerto Rican female adolescent participants showed PA levels below the minimal recommendation for health. School-based health promotion interventions designed to help increase PA levels in this population must consider parental involvement.

Key Words: IPAQ, accelerometer, physical inactivity, sedentary lifestyle

RESUMEN

Álvarez, A.J., Ramírez Marrero, F.A., Ortiz, A. y Martínez L.R. (2013). Niveles de actividad física en mujeres adolescentes en Puerto Rico: un estudio piloto. Pensar en Movimiento: Revista de Ciencias del Ejercicio y la Salud, 11 (1), 1-12. Durante la adolescencia, las mujeres son particularmente propensas a la inactividad física, el sobrepeso y eventualmente la obesidad. La obesidad entre niños y adolescentes es un problema de salud públicaen Puerto Rico (PR); sin embargo, no existe suficiente información sobre la Actividad Física (AF) en esta población. El propósito de este estudio fue evaluar los niveles de AF y factores que influyen la AF entre mujeres adolescentes en PR. Cuarenta participantes divididas en dos grupos de acuerdo a la edad (11-12 y 14-16 años), utilizaron un acelerómetro durante seis días y completaron un cuestionario de AF. Los padres de familia completaron un cuestionario socio-demográfico y también de AF. Se utilizaron pruebas t para muestras independientes y ANOVA para identificar diferencias en la AF moderada a vigorosa (AFMV) por grupo de edad y entre las adolescentes y sus padres de familia. También se utilizó una regresión múltiple para identificarfactores relacionados con la AF. La AFMV promedió 87(54) minutos/semana sin haber diferencias por grupo de edad: 11-13 años, 87(58) y 14-16 años, 86(50) minutos/semana (p=.95) y esta correlacionó significativamente con la AFMV reportada por los padres de familia (r=0.67, p<.01). La AFMV de los padres de familia y el número de días que los padres de familia compartieron AF con sus hijas fueron los factores con mayor capacidad de predicción de la AFMV de las adolescentes. El nivel de AF entre las adolescentes participantes estuvo por debajo del mínimo recomendado. En intervenciones para promover la AF entre mujeres adolescentes en PR se debe tomar en cuenta la participación de los padres de familia.

Palabras claves:IPAQ, acelerómetro, inactividad física, sedentarismo

Physical activity (PA) is defined as body movement produced by skeletal muscle activation resulting in energy expenditure above resting levels (American College of Sports Medicine [ACSM], 2010). It is known that adolescents who keep high levels of PA have a better control of body weight, lower blood cholesterol levels, and lower risk of developing type 2 diabetes (Cairella et al., 2007; Raitakari et al., 1994) .

Physical inactivity and sedentary time, on the other hand, are important factors that help explain the growing prevalence of overweight and obesity among adolescents (Berkey, Rockett, Gillman, & Colditz, 2003;Gordon-Larsen, Adair, Nelson, & Popkin, 2004) .Obese adolescents are at a high risk of becoming obese adults, and also at a higher risk of experiencing obesity-related comorbidities such as hyperlipidemia, hypertension, and glucose intolerance(Trost, Kerr, Ward, & Pate, 2001).

The PA recommendation for youth suggests that school age children and adolescents (6-18 years of age) must engage in at least 60 minutes of daily moderate-to-vigorous physical activities (MVPA) that are fun, appropriate for their developmental stage, and that integrate a variety of activities (Strong et al., 2005;U.S. Department of Health and Human Services [USDHSS], 2008) . However, research shows that children’s MVPA is low (<60 minutes/day) and decreases during adolescence, particularly among women (Riddoch et al., 2004; Telama & Yang, 2000; Trost et al., 2002) . Similar to the United States (US), the incidence and prevalence of obesity among children and adolescents have been growing in Puerto Rico (PR), and also growing are the health complications associated with overweight, obesity and lack of physical activity in this population (Venegas, Perez, Suarez, &Guzman, 2003). It has been estimated that 47% of adolescents in PR are overweight or obese, and high blood pressures have been detected among obese compared with non-obese adolescents (Venegas, et al., 2003). A more recent study also showed that 80% of adolescents in PR do not comply with the PA recommendation (Vigo-Valentín, Hodge, & Kozub, 2011). In that study, PA was evaluated with self-reports.

There are no published data regarding objectively assessed PA levels among adolescent females in PR.  Therefore, the purpose of this study was to evaluate PA levels in a group of adolescent females in PR using accelerometers, and to identify factors that influence their regular engagement in PA. The hypotheses of this study are: 1) PA levels in the group of adolescent females will be below the recommended level for youth, 2) older female adolescents will have a lower PA level compared with younger female adolescents, and 3) sociodemographic factors and parent’s PA will be related to the PA level of female adolescents. 

Methods

Study participants. A convenience sample of 40 female adolescents (24 between 11-13, and 16 between 14-16 years of age)and one of their parents (33 mothers and seven fathers) were recruited from the University of Puerto Rico Laboratory School in San Juan, PR. This sample size provided a statistical power of 95% (alpha < .01) to detect a 50% difference between the recommended MVPA and the MVPA of the female adolescent participants.
The Committee for the Protection of Human Subjects in Research of the University of Puerto Rico, Río Piedras Campus, approved the informed consent and assent forms that were signed by parents and female adolescents, respectively, prior to study initiation.

Instruments.The assessment of MVPA among female adolescents was obtained with an objective instrument (GT1M accelerometer, Actigraph™, Pensacola, FL) and a subjective one (short version of the International Physical Activity Questionnaire (IPAQ, 2005). The accelerometer was used to evaluate PA during six consecutive days including at least one weekend day. Although participants were asked to start wearing the accelerometer immediately, actual recordings started on the following day. Accelerometers were placed and collected back during school time between Monday and Friday. A minimum of 10 hoursof recording was considered a full day of measurements. Accelerometer activity counts were used to determine minutes/day of moderate (1500-2600 counts·30s-1) and vigorous (> 2,600 counts·30s-1) PA following recommendations for this age group (Treuth et al., 2004) . The IPAQ was used to obtain the self-reported PA among the female adolescents and their parents by calculating the minutes/day of moderate PA, vigorous PA, the combination of both (MVPA), and the self-reported sitting time according to established guidelines for this instrument (IPAQ, 2005). A question about usual sleeping time was added to the instrument. The minutes/week of MVPA were then calculated with the IPAQ for the female adolescents and their parents, and with the accelerometer for the female adolescents.
Sociodemographic characteristics that have been previously associated with physical activity behavior (Bauer, Neumark-Sztainer, Fulkerson, Hannan, & Story, 2011; Trost, et al., 2001) were evaluated with a questionnaire in which parents reported their annual income, years of education, marital status, occupation, smoking habits, access to recreational facilities, days per week in which they shared physical activities with their daughter, and perception of their current general health. Data was collected between January and March of 2008.

Study protocol. After obtaining authorization from School Officials, orientation about the research objectives and protocol was given to potential participants in their classrooms. Informative flyers were distributed to all interested female adolescents so that they could bring the information to their parents. An initial screening was conducted to identify those who met the inclusion criteria after parents signed the informed consent and each daughter participant signed the assent form. The inclusion criteria were: 1) ability to engage in ambulatory physical activities (e.g., walk), 2) no pregnancy or diagnosed cardiovascular, metabolic, or orthopedic disorder, and 3) post-menarche.

Parents completed the sociodemographic questionnaire and the IPAQ during an interview with the principal investigator. After measuring height with a stadiometer and weight with a digital scale, female adolescents were instructed about the proper use of the accelerometer (placementon the side above the hip bone, adhered to an elastic band worn around the waist)and were asked to wear it all the time except to shower or to sleep at night. Participants received a daily morning phone call in which the principal investigator reminded them of the proper use of the accelerometer. The following day after completing the evaluation period with accelerometers, participants met individually with the principal investigator to return the accelerometer and complete the IPAQ by interview. A question regarding hours of night sleep was also included.

Data analyses.Descriptive analyses (means (standard deviations), and proportions) were used to summarize all variables of interest. A two-way analysis of variance (ANOVA) was used to test for significant differences in MVPA of female adolescent participants by age group (11-13 vs. 14-16 years) and by instrument (IPAQ vs. accelerometer). An independent t-test and regression analysis were also used to identify differences and associations between: 1) recommended minutes/day of MVPA and accelerometer determined minutes/day of MVPA of female adolescent participants, 2) self-reported minutes/day of MVPA between female adolescents and their parents. Finally, a step-wise regression analysis was conducted to evaluate factors that might influence physical activity behavior among the female adolescent participants (family annual income, years of education among their parents, access to recreational facilities, PA of their parents, days/week that participants share PA with their parents). A .05 alpha was selected a priori to detect significant differences or associations. Data was analyzed with the STATA software (version 9.1, STATA Statistic/Data Analysis Package, 2006, STATA Corp., College Station, Texas).

Results
  Descriptive characteristics of female adolescent participants and their parents are summarized in Table1. Based on the age and sex specific percentile of body mass index (BMI) for children and adolescents (www.cdc.gov/healthyweight/assessing/bmi/, accessed on October 22, 2012), 15% (6/40) of the female adolescents were classified as obese, 20% (8/40) as overweight, and 65% (26/40) as normal weight. Body weight, height and BMI were not different by age group. Age and BMI of parents were 44.5 (6.0)yearsand 26.5 (4.1) kg/m2, respectively. Based on adult BMI analysis, 15% (6/40) of parents classified as obese, 25% (17/40) as overweight, 40% (16/40) as normal weight, and 3% (1/40) as underweight.

Sociodemographic characteristics are presented in Table 2. The majority of parents were mothers (83%). A high proportion of parents (85%) reported having at least a college degree, and 63% reported a relatively high annual income.Although 61% of parents reported having Access to recreational facilities, only 24% engaged in physical activities with their daughters.

Self-reported PA with the IPAQ among female adolescents and their parents, and accelerometer-determined PA among female adolescents are presented in Table3. Minutes/week of MVPA among female adolescents (range: 20 to 238 minutes/week) were significantly lower than the recommended minimum of 300 minutes/week for this population (USDHHS, 2008). None of the female adolescents in this study reached the minimum PA recommendation, and only 10% reached at least 150 min/week of MVPA, the minimum PA recommendation for adults (USDHHS, 2008). Among these female adolescents, self-reported MVPA was significantly higher compared with the accelerometer (388.4 (202.7) vs. 86.9 (54.2) minutes/week, respectively; p = .001). The parent’s self-reported MVPA and sitting time are also included in Table 3, with mean values of 696.5 (713.8) minutes/week of MVPA, and 6.7 (2.6) hours/day of sitting time

Table 1.

Descriptive characteristics of female adolescents by age group and their parents

Note: BMI = Body mass index, *p< .05

Table 2.

Sociodemographic characteristics as reported by parents (n = 40)

Table 3.

Mean (M) and standard deviation (SD) of physical activity variables among female adolescents as determined with the accelerometer and self-reported with the IPAQ, and self-reported physical activity with the IPAQ among parents.

Note: PA = Physical activity, MVPS = moderate to vigorous physical activity

  The MVPA among female adolescents by age group and by instrument (IPAQ vs. ActiGraph accelerometer) is presented in Figure 1. Accelerometer-determined and self-reported PA were mostly of moderate intensity while very little time was spent in vigorous intensity PA (p = .001).
Among possible factors influencing the female adolescents PA behavior, sharing PA with their parents and parent’s PA were the two most significant (t =2.64, p= .01; and t=2.21, p = .03; respectively) explaining 27% of the variance in the adolescent’s MVPA (F2,37 =6.82, p < .01).