ABSTRACT
Objectives.
Physical activity, fitness and nutrition influence health trajectories from childhood to adulthood and are linked to the risk of chronic diseases. Despite the urgency of prevention, there is a lack of longitudinal data about these health indicators among children in Puerto Rico. This 3-year study (2013–2016) followed 46 children from ages 7 to 9 years to assess their physical activity, fitness, nutrition and self-efficacy over time, and to explore the interrelationships among these indicators.
Methods
Physical activity was measured using accelerometers, fitness via the FitnessGram assessment protocol, nutrition through 3-day dietary recall and self-efficacy with a questionnaire. Statistical analyses included repeated measures of analysis of variance, logistic regression and Spearman’s correlations.
Results
Throughout the study, most participants failed to meet the physical activity guidelines for Americans, with girls being consistently less active and having higher percentages of body fat than boys. Fitness levels declined over time, particularly muscular strength and endurance. Self-efficacy was positively associated with muscular fitness and body composition. Despite caloric intake falling within general age-appropriate recommendations, the low levels of physical activity suggest there may be an imbalance between energy intake and expenditure.
Conclusions
Early sex disparities in physical activity and fitness, coupled with low self-efficacy and high levels of sedentary time, underscore the urgent need for public health initiatives and school-based interventions that promote active lifestyles, improve nutrition and build self-efficacy, especially among girls. Schools are uniquely positioned to implement evidence-based strategies that can foster healthier behaviors and reduce long-term health risks among youth.
Keywords: Physical fitness, activity trackers, nutrition assessment, Hispanic
RESUMEN
Objetivos
La actividad física, el estado físico y la nutrición influyen en la salud desde la infancia hasta la edad adulta y están relacionados con el riesgo de padecer enfermedades crónicas. Si bien es urgente implementar medidas de prevención en salud, no hay datos longitudinales sobre estos indicadores de salud en la población infantil de Puerto Rico. En este estudio, llevado a cabo entre el 2013 y el 2016, se realizó un seguimiento de 46 menores de entre 7 y 9 años para evaluar su actividad física, estado físico, nutrición y autoeficacia a lo largo del tiempo, y explorar las interrelaciones entre estos indicadores.
Métodos
La actividad física se determinó mediante acelerómetros; el estado físico, con el protocolo de evaluación FitnessGram; la nutrición, mediante el recuerdo de alimentación de tres días; y la autoeficacia, con un cuestionario. En los análisis estadísticos se utilizaron mediciones repetidas de análisis de la varianza, regresión logística y correlaciones de Spearman.
Resultados
A lo largo del estudio, la mayoría de los participantes no cumplieron las directrices de actividad física recomendadas para la población estadounidense; las niñas realizaban menos actividad física y presentaban un porcentaje de grasa corporal mayor que los niños. La evaluación del estado físico puso de manifiesto una disminución con el transcurso del tiempo, en especial por lo que respecta a la fuerza muscular y la resistencia. La autoeficacia presentó una asociación positiva con la función muscular y la composición corporal. A pesar de que el consumo calórico se ajustaba a las recomendaciones generales adecuadas para la edad, los niveles bajos de actividad física sugieren un desequilibrio entre el consumo y el gasto energético.
Conclusiones
Las desigualdades tempranas entre los niños y las niñas en cuanto a la actividad física y el estado físico, junto con unos niveles bajos de autoeficacia y unos niveles altos de sedentarismo, subrayan la necesidad urgente de diseñar iniciativas de salud pública e intervenciones escolares que promuevan estilos de vida activos, mejoren la nutrición y fomenten la autoeficacia, en especial en las niñas. Las escuelas se encuentran en una posición privilegiada para implementar estrategias basadas en la evidencia que fomenten comportamientos más saludables y reduzcan los riesgos para la salud a largo plazo en la población infantil.
Palabras clave: Aptitud física, monitores de ejercicio, evaluación nutricional, Hispánico
RESUMO
Objetivos
A atividade física, a aptidão física e a nutrição influenciam a trajetória da saúde desde a infância até a idade adulta e estão associados ao risco de doenças crônicas. Apesar da urgência da prevenção, faltam dados longitudinais sobre esses indicadores de saúde entre as crianças em Porto Rico. Este estudo com duração de três anos (2013–2016) acompanhou 46 crianças de 7 a 9 anos para avaliar sua atividade física, aptidão física, nutrição e autoeficácia ao longo do tempo, bem como para explorar as interrelações entre esses indicadores.
Métodos
A atividade física foi medida com o uso de acelerômetros, a aptidão física por meio do protocolo de avaliação FitnessGram, a nutrição por meio de um recordatório alimentar dos últimos três dias e a autoeficácia por meio de um questionário. As análises estatísticas incluíram medidas repetidas de análise de variância, regressão logística e correlações de Spearman.
Resultados
Ao longo do estudo, a maioria dos participantes não atenderam às diretrizes de atividade física para estadunidenses, e as meninas se mostraram invariavelmente menos ativas e apresentaram porcentagens de gordura corporal mais altas do que as dos meninos. Os níveis de aptidão física diminuíram com o tempo, principalmente a força e a resistência muscular. A autoeficácia teve uma associação positiva com o condicionamento muscular e a composição corporal. Apesar de a ingestão calórica estar dentro das recomendações gerais adequadas para a idade, os baixos níveis de atividade física sugerem que pode haver um desequilíbrio entre a ingestão e o gasto de calorias.
Conclusões
As disparidades precoces entre os sexos na atividade física e na aptidão física, aliadas a baixa autoeficácia e altos níveis de sedentarismo, ressaltam a necessidade urgente de iniciativas de saúde pública e intervenções escolares que promovam estilos de vida ativos, melhorem a nutrição e desenvolvam a autoeficácia, sobretudo entre as meninas. As escolas têm tudo para implementar estratégias baseadas em evidências capazes de promover comportamentos mais saudáveis e reduzir os riscos no longo prazo para a saúde entre os jovens.
Palavras-chave: Aptidão física, monitores de aptidão física, avaliação nutricional, Hispânico
Engaging in physical activity, being physically fit and ensuring healthy nutrition are significant factors that influence health trajectories from childhood into adulthood. These factors are critical in preventing chronic diseases such as obesity, cardiovascular disease and type-2 diabetes (1–4). However, a growing body of evidence highlights a troubling trend: children and adolescents in both the United States and Puerto Rico exhibit high rates of physical inactivity and poor dietary habits, and there is an increasing prevalence of obesity (5–8).
According to national surveys, more than 70% of adolescents in the USA and Puerto Rico fail to meet the recommendation to engage in 60 minutes of moderate-to-vigorous physical activity (MVPA) every day (5, 6, 8). Physical activity levels tend to decline further during the transition from childhood to adolescence (9, 10). Concurrently, dietary patterns among youth are characterized by excessive caloric intake and poor nutritional quality, contributing to a higher prevalence of obesity in Puerto Rico (23%) compared with the USA (18%) (5–10).
Beyond physical health, physical activity and fitness are closely linked to psychological well-being (11). Perceived self-efficacy – that is, the belief in one’s ability to succeed in specific situations – is an important component of psychological well-being that plays a pivotal role in shaping health behaviors, including deciding whether to engage in physical activity and to make healthy dietary choices (12, 13). Conversely, sedentary behaviors have been associated with lower psychological well-being and reduced interest in physical activities (14). These interrelationships underscore the importance of examining levels of physical activity and fitness, nutrition, and self-efficacy together, particularly during the formative elementary school years.
Despite the urgency of these issues, there is a lack of longitudinal data about these health indicators among children in Puerto Rico. National data sets often exclude United States territories, in this case, leaving a critical gap in understanding the health behaviors and needs of Puerto Rican youth. To address this gap, the University of Puerto Rico’s Río Piedras Campus launched the first longitudinal study of physical activity, physical fitness, self-efficacy and nutrition in children. The study aimed to describe the physical activity, fitness, self-efficacy, and energy and macronutrient intake of elementary school children living in Puerto Rico, and examine sex- and age-related associations among these variables during a 3-year period.
MATERIALS AND METHODS
This longitudinal study followed a cohort of 46 children (23 girls, 23 boys) from the ages of 7 to 9 years in San Juan, Puerto Rico, from 2013 to 2016. Recruitment involved school presentations, informational booths, and meetings with parents and teachers. Participants received non-monetary, health-promoting incentives upon completing the study. Written informed consent was obtained from parents, and assent was obtained from participating children prior to data collection. The study was reviewed by and received ethical approval from the Institutional Review Board of the University of Puerto Rico, Río Piedras Campus. The study was implemented in accordance with the Declaration of Helsinki. Measurements were taken during the second school semester of each academic year during the 3-year period.
Physical activity and sedentary time, representing two distinct but interconnected dimensions of health behavior, were assessed with ActiGraph GT3X+ accelerometers (Ametris, Pensacola, FL) worn on the hip for 24 hours/day for 8 consecutive days, although data from the first day were excluded to control for reactivity bias. Devices were initialized to collect data at a rate of 90 Hz, and data were downloaded in raw format using ActiLife software (v. 6.11.4 and 6.11.6, Ametris). Raw data were processed using the R open-source programming language (v. 4.3.3, R Core Team, Vienna, Austria) (15, 16). First, the device’s analog voltage signal was converted to raw counts via full-wave rectification and integrated into 1-second epochs. Then, the maximum value within each epoch was selected to represent the count value for that epoch. Finally, the raw counts for each 1-second epoch were reintegrated to match the required epochs of the algorithms for wear-time validation (60 s) and classification (15 s). Wear-time was validated using the algorithm by Choi et al. (17), with the non-wear period defined as having a minimum length of 90 minutes, a small window length of 30 minutes and a spike tolerance of 2 minutes. Additionally, only participants with at least 10 hours of wear time per day for at least 3 days/week, including at least one weekend day, were included in further analyses. Sleep time was removed by setting time constraints generated from visual inspection of the data for each participant. Cut-points for counts for the children were derived from Evenson et al. (18) and used to estimate physical activity and sedentary time: sedentary time was set at 0–25, light physical activity (LPA) at 26–573, moderate physical activity (MPA) at 574–1002 and vigorous physical activity (VPA) at ≥ 1003. The amount of MVPA was obtained by combining the totals for MPA and VPA. Daily averages for MVPA and sedentary time were calculated based on the number of valid days.
Health related physical fitness was assessed using the FitnessGram test battery (GreenLight Fitness, Dallas, TX) (19), which includes three tests for muscular strength and endurance (i.e. curl-ups, push-ups and trunk lift), two tests for flexibility (i.e. left and right back-saver sit and reach, and shoulder stretch) and two tests for body composition (i.e. body mass index [BMI] and percentage of body fat). These tests were administered by trained staff during each school’s physical education classes. Healthy Fitness Zone criteria, a measure of performance associated with health benefits, were applied to determine achievement in each component. The fitness performance standards were established by the Kenneth H. Cooper Institute, at the Texas Tech University Health Sciences Center, to protect against diseases associated with sedentary living. BMI percentiles were calculated using the U.S. Centers for Disease Control and Prevention growth charts, and the percentage of body fat was estimated using Slaughter et al.’s (20) skinfold equations.
Self-efficacy was measured using the Spanish version of the 12-item Physical Activity Self-Efficacy Scale, which elicits binary responses (i.e. yes/no) (21). Scores range from 0 to 12, with scores ≥9 indicating high self-efficacy. The questionnaire has been validated among children (22) to assess confidence in overcoming barriers, seeking support and identifying different options for engaging in physical activity.
Nutritional intake was assessed using 3 days of diet recall (i.e. for two non-consecutive weekdays and one weekend day), with surveys completed at home with parental assistance and verified through structured interviews by supervised nutrition interns using food model replica kits to estimate portion sizes. Interviews were conducted in the morning on the day after the 24-hour diet recall, using specific questions about what children ate the day before, and data were collected on paper. For each of the three years, interviews were conducted during the same period and at the same time point during the academic year. Macronutrient and caloric intake were analyzed using Nutritionist Pro software (version 7.6, Axxya Systems, Redmond, WA). To estimate energy balance, energy intake was compared with the values recommended for the level of physical activity by the 2020–2025 U.S. dietary guidelines for Americans (23).
Descriptive statistics – that is, means and standard deviations (SD) for continuous variables and proportions for categorical variables – were computed to summarize participants’ characteristics. If the assumption of normality was not met, a non-parametric alternative was considered. Spearman’s correlation coefficients were used to assess relationships among physical activity, fitness, self-efficacy and nutrition. Multiple comparisons were performed and adjusted using the Bonferroni approach for post hoc comparisons. To evaluate changes across years and differences by sex, a generalized linear model was used with a binary response for repeated measure of analysis of variance (or ANOVA). Analyses were conducted using the open-source R programming language (v. 4.5.1), with statistical significance set at P < 0.05.
RESULTS
Descriptive findings are summarized in Table 1, and Figures 1–3 present the proportion of participants achieving the Healthy Fitness Zone criteria. Across all three years, the average daily MVPA for all ranged from 39 to 48 minutes, with girls consistently engaging in less MVPA than boys. MVPA declined significantly from age 7 to age 8 (P = 0.006), with no further decline observed at age 9. Only one boy, aged 9, in the third year of the study achieved the recommended 60 minutes/day of MVPA (data not shown). Sedentary time remained stable at approximately 6 hours/day, with no significant differences between sexes or across years.
TABLE 1. Physical activity, physical fitness, self-efficacy and nutrition characteristics in 46 children (23 girls and 23 boys), by study year and sex.
|
Variablea |
First evaluation |
Second evaluation |
Third evaluation |
||||||
|---|---|---|---|---|---|---|---|---|---|
|
All |
Boys |
Girls |
All |
Boys |
Girls |
All |
Boys |
Girls |
|
|
Age (years) |
7.1 ± 0.3 |
7.1 ± 0.3 |
7.0 ± 0.0 |
8.1 ± 0.3 |
8.1 ± 0.3 |
8.0 ± 0.0 |
9.1 ± 0.3 |
9.1 ± 0.3 |
9.0 ± 0.0 |
|
Weight (kg) |
28.1 ± 6.8 |
26.7 ± 6.3b |
29.5 ± 7.2 |
31.6 ± 7.9c |
29.8 ± 7.9b |
34.4 ± 7.6 |
33.7 ± 9.4b |
37.2 ± 8.8 |
|
|
Height (cm) |
125.8 ± 6.4 |
124.8 ± 6.5b |
126.7 ± 6.4 |
131.0 ± 6.6c |
130.2 ± 6.3b |
131.9 ± 6.8 |
135.8 ± 6.7 |
138.8 ± 7.6 |
|
|
Physical activity | |||||||||
|
Moderate to vigorous physical activity (min/day) |
48.1 ± 22.2 |
57.5 ± 25.7 |
38.8 ± 12.8 |
40.2 ± 18.3c |
45.3 ± 21.9b |
35.1 ± 12.5 |
38.8 ± 19.9c |
45.4 ± 23.1b |
32.4 ± 13.9 |
|
Sedentary (h/day) |
6.0 ± 1.1 |
6.0 ± 1.0 |
6.0 ± 1.2 |
6.3 ± 1.5 |
6.2 ± 1.5 |
6.5 ± 1.5 |
6.5 ± 1.7 |
6.3 ± 1.9 |
6.6 ± 1.4 |
|
Physical fitness | |||||||||
|
No. of curl-ups |
11 ± 6 |
10 ± 6 |
12 ± 7 |
12 ± 7 |
12 ± 8 |
13 ± 7 |
14 ± 9 |
14 ± 7 |
13 ± 10 |
|
No. of push-ups |
7 ± 8 |
6 ± 6 |
8 ± 10 |
7 ± 7 |
8 ± 7 |
6 ± 7 |
6 ± 5 |
7 ± 5b |
4 ± 5c |
|
Trunk lift (inches) |
7.1 ± 2.1 |
6.9 ± 1.9 |
7.4 ± 2.3 |
7.0 ± 1.4 |
6.7 ± 1.7 |
7.4 ± 1.1 |
7.2 ± 2.0 |
7.0 ± 1.9 |
7.4 ± 2.1 |
|
Left sit and reach (inches) |
11.4 ± 2.5 |
11.1 ± 2.3 |
11.7 ± 2.7 |
10.3 ± 2.5c |
9.9 ± 2.6c |
10.7 ± 2.4c |
10.3 ± 2.5c |
10.2 ± 2.3 |
10.3 ± 2.7c |
|
Right sit and reach (inches) |
11.3 ± 2.3 |
11.1 ± 2.2 |
11.5 ± 2.5 |
10.6 ± 2.5c |
10.3 ± 2.6c |
10.9 ± 2.5 |
10.6 ± 2.6c |
10.2 ± 2.6 |
11.0 ± 2.6 |
|
Left shoulder stretch (% able to accomplish) |
80.4 |
73.9 |
87.0 |
88.9 |
95.5 |
82.6 |
89.1 |
91.3 |
87.0 |
|
Right shoulder stretch (% able to accomplish) |
78.3 |
73.9 |
82.6 |
93.3c |
90.9 |
95.7 |
95.7c |
91.3 |
100.0 |
|
BMI (kg/m2) |
17.6 ± 2.9 |
17.0 ± 2.5 |
18.2 ± 3.2 |
18.1 ± 3.1c |
17.3 ± 2.9 |
19.0 ± 3.1c |
18.6 ± 3.2c |
19.2 ± 3.4c |
|
|
BMI percentile |
66.0 ± 30.9 |
61.4 ± 32.2 |
70.6 ± 29.6 |
66.7 ± 28.0 |
59.6 ± 29.5 |
73.7 ± 25.0 |
64.3 ± 30.8 |
60.4 ± 32.1 |
68.2 ± 29.6 |
|
BMI classification (%) Underweight Normal weight Overweight Obese |
2.2 58.7 13.0 26.1 |
4.3 65.2 8.7 21.7 |
0.0 52.2 17.4 30.4 |
2.2 60.9 13.0 23.9 |
4.3 69.6 8.7 17.4 |
0.0 52.2 17.4 30.4 |
4.3 60.9 17.4 17.4 |
8.7 60.9 17.4 13.0 |
0.0 60.9 17.4 21.7 |
|
Body fat (%) |
19.4 ± 8.3 |
16.0 ± 8.0b |
22.9 ± 7.2 |
20.4 ± 8.6c |
23.3 ± 6.8 |
||||
|
Self-efficacy | |||||||||
|
Score |
9.3 ± 1.5 |
9.2 ± 1.6 |
9.2 ± 2.0 |
9.5 ± 1.9 |
9.2 ± 2.0 |
9.8 ± 1.8 |
10.1 ± 1.6 |
10.3 ± 1.6 |
9.9 ± 1.7 |
|
Positive score (%) |
77.2 ± 12.4 |
76.5 ± 13.7 |
76.8 ± 16.9 |
79.2 ± 15.9 |
76.8 ± 16.9 |
81.5 ± 14.9 |
84.1 ± 13.6c |
85.9 ± 12.9 |
82.3 ± 14.3 |
|
Nutrition | |||||||||
|
Total kcal |
1 871 ± 479 |
1 842 ± 446 |
1 900 ± 518 |
1 887 ± 454 |
1 905 ± 517 |
1 868 ± 392 |
1 912 ± 561 |
1 925 ± 607 |
1 899 ± 524 |
|
Carbohydrates (%) |
66.7 ± 5.0 |
67.4 ± 3.1 |
66.0 ± 3.2 |
65.5 ± 4.7 |
65.4 ± 5.1 |
65.5 ± 4.3 |
63.1 ± 7.0c |
63.6 ± 8.1 |
62.6 ± 5.7 |
|
Fats (%) |
16.9 ± 2.8 |
16.6 ± 2.6 |
17.2 ± 2.5 |
18.0 ± 3.3c |
17.8 ± 3.8 |
18.3 ± 2.7 |
20.6 ± 7.2c |
20.5 ± 8.1 |
20.8 ± 6.8 |
|
Proteins (%) |
16.4 ± 4.1 |
16.1 ± 5.2 |
16.8 ± 2.5 |
16.5 ± 2.8 |
16.8 ± 2.8 |
16.2 ± 2.8 |
16.3 ± 3.6 |
16.0 ± 4.4 |
16.6 ± 3.0 |
BMI: body mass index.
Values are mean (standard deviation) unless otherwise indicated.
P < 0.05 by sex in each year.
P < 0.05 compared with first year.
P < 0.05 compared with second year.
Source: Table prepared by the authors based on the results of their study.
FIGURE 1. Percentage of 46 children meeting Healthy Fitness Zone criteria for muscular strength and endurance, by study year and sex, Puerto Rico, 2013–2016.
a Data compared with the first year: odds ratio = 0.74, 95% confidence interval: 0.047 to 0.849.
b Data differed by sex in the third year: odds ratio = 3.68, 95% confidence interval: 1.08 to 16.86.
Source: Figure prepared by the authors based on the results of their study.
FIGURE 3. Percentage of 46 children meeting the Healthy Fitness Zone criteria for body composition, by study year and sex, Puerto Rico, 2013–2016.
a For boys compared with girls, the odds ratios (OR) and 95% confidence intervals (CI) are OR = 2.71, 95% CI: 1.06 to 11.84 for year 1, OR = 2.82, 95% CI: 1.07 to 12.62 for year 2, and OR = 2.43, 95% CI: 1.57 to 10.43 for year 3.
Source: Figure prepared by the authors based on the results of their study.
The tests for muscular strength and endurance revealed no significant differences between the sexes in curl-up or trunk-lift performance (Table 1). However, boys performed significantly more push-ups than girls at age 9 (year 3) (P = 0.042). Over time, the proportion of children meeting the Healthy Fitness Zone criteria for muscular strength and endurance (Figure 1) declined from 83% (38/46) at age 7 (year 1) to 59% (27/46) at age 9 (odds ratio [OR] = 0.74, 95% confidence interval [CI]: 0.047 to 0.849). At age 9, only 44% (10/23) of girls met the Healthy Fitness Zone standard compared with 74% (17/23) of boys (OR = 3.68, 95% CI: 1.08 to 16.86).
No differences were found between the sexes in the sit-and-reach or shoulder stretch tests of flexibility (Table 1). However, flexibility declined over time in both sexes. Girls showed reduced sit-and-reach left-leg flexibility, while boys showed reduced right-leg flexibility at ages 8 and 9 compared with age 7 (compared with age 7, at age 8, P = 0.02 for girls and P = 0.04 for boys, and for age 9, P = 0.01 for girls and P = 0.11 for boys) (Table 1). The proportion of children meeting the Healthy Fitness Zone criteria for flexibility (Figure 2) increased slightly at age 8 (year 2) to 72% (33/46; OR = 1.34, 95% CI: 1.33 to 1.34), but declined at age 9 to 65% (30/46; OR = 0.80, 95% CI: 0.795 to 0.799).
FIGURE 2. Percentage of 46 children meeting the Healthy Fitness Zone criteria for flexibility, by study year and sex, Puerto Rico, 2013–2016.
a Data compared with the first year 1, odds ratio = 1.34, 95% confidence interval: 1.33 to 1.34.
b Data compared with the first and second years, odds ratio = 0.80, 95% confidence interval: 0795 to 0.799.
Source: Figure prepared by the authors based on the results of their study.
Height and weight increased each year for both sexes, as expected (Table 1). While BMI percentiles did not differ significantly by sex, girls had consistently higher percentages of body fat across all three years. Among girls, body fat increased significantly at age 9 compared with ages 7 and 8 (P = 0.02 for age 9 compared with age 7; P < 0.001 for age 9 compared with age 8). Boys also showed a yearly increase in body fat (P = 0.002 for age 8 compared with age 7; P < 0.001 for age 9 compared with ages 7 and 8). The proportion of boys meeting the Healthy Fitness Zone criteria for body composition (Figure 3) was significantly higher than it was for girls in all years.
Mean self-efficacy scores ranged from 9.2 to 10.3, with no significant differences between the sexes. However, 43% of participants (9 boys, 11 girls) reported low self-efficacy (<9 points) during at least one or two years (data not shown), and 7% of children (1 girl, 2 boys) consistently reported low self-efficacy across all three years. The mean (SD) percentage of positive responses on the self-efficacy questionnaire increased significantly from 77.2% ± 12.4% at age 7 to 84.1% ± 13.6% at age 9 (P = 0.023) (Table 1).
The nutritional analysis revealed that the average daily caloric intake ranged from 1842 to 1925 kcal, with no significant differences by sex or year. Macronutrient distribution was mostly within recommended ranges: 63–67% carbohydrates (the recommendation is 45–65%), 17–21% fats and 16–17% protein. However, carbohydrate intake declined at age 9, while fat intake increased at ages 8 and 9 compared with age 7. When energy intake was compared with the dietary guidelines for Americans (23) for children with very low levels of activity or sedentary children, we estimated that energy intake likely exceeded energy expenditure.
Findings from the correlational analyses for complete measures showed that MVPA was positively correlated with favorable body composition (Healthy Fitness Zone achievement, Spearman’s ρ = 0.28, P < 0.05). Sedentary time was negatively correlated with body composition (Spearman’s ρ = −0.22, P < 0.05) and flexibility (sit-and-reach, Spearman’s ρ = −0.31, P < 0.05). Self-efficacy was positively correlated with both muscular strength and endurance, and body composition (Healthy Fitness Zone achievement, Spearman’s ρ = 0.19, P < 0.05, for both). No significant correlations were found between MVPA and self-efficacy or nutrition, nor between Healthy Fitness Zone outcomes and nutrition.
DISCUSSION
This study is the first to longitudinally examine physical activity, physical fitness, self-efficacy and nutrition among elementary school children in Puerto Rico. Over a 3-year period, this study observed persistently low physical activity levels, high levels of sedentary time and increasing percentages of body fat, with notable disparities between boys and girls emerging as early as age 7.
Physical activity and sedentary time
Consistent with previous research, boys were more physically active than girls, with girls consistently falling below recommended levels for MVPA (24–29). However, even among boys, levels of MVPA were substantially lower than those reported in other international studies. For example, while boys in this study averaged 45 to 58 minutes of MVPA per day and girls averaged 32 to 39 minutes of MVPA per day, prior studies have reported 71 to 111 minutes for boys and 56 to 77 minutes for girls (24–26). Potential explanations for these differences include environmental, structural and behavioral factors, such as limited access to safe parks and recreational spaces, limited access to extracurricular activities, urban infrastructure that discourages walking, and parental lack of time and resources. Only one participant met the 60-minute MVPA guideline by the final year of the study, underscoring the severity of physical inactivity in this population.
Sedentary time remained stable at approximately 6 hours/day, aligning with other studies, but still exceeding recommended limits (25–26). Although there is no universal threshold that defines excessive sedentary time for children, current guidelines advocate for minimizing prolonged sitting and limiting recreational screen time to less than 2 hours daily (30–31).
Physical fitness
Fitness outcomes revealed a concerning decline in muscular strength and endurance over time, particularly among girls. While flexibility benchmarks were more frequently achieved, performance declined in the later years of the study. These findings mirror trends observed in children in the USA, where fitness levels tend to decrease with age, especially among girls (31).
Girls consistently had higher percentages of body fat and were less likely to meet Healthy Fitness Zone standards for body composition. This disparity in Healthy Fitness Zone achievement may reflect both lower levels of physical activity and higher energy intake relative to low levels of physical activity. The decline in fitness performance, especially among girls, highlights the early onset of sex-based health disparities and the need for targeted interventions.
Self-efficacy
Although average self-efficacy scores were relatively high and similar between the sexes, nearly half of the children reported low self-efficacy during at least one year. This variability suggests that confidence in engaging in physical activity may fluctuate during early childhood. Importantly, higher self-efficacy was positively associated with better body composition and muscular fitness, reinforcing its role as a key psychological factor in promoting healthy behaviors. It has been suggested that parental support and structured physical activities during school recess could help promote self-efficacy for physical activity among school-aged children (32, 33).
Nutrition
Caloric intake was within general age-appropriate recommendations (23, 34), but at the highest level recommended for active children in each age group. However, when this was considered alongside low levels of physical activity, it suggests there is an energy imbalance. The increase in the consumption of fat was also concerning. These dietary patterns, combined with insufficient physical activity (23), likely contributed to the observed increases in body fat.
Interrelationships and implications
Our findings support established associations between sedentary time and poorer flexibility (35). Additionally, children with better fitness outcomes had higher self-efficacy scores, suggesting a reinforcing cycle between physical and psychological health. These results align with prior studies linking physical activity and fitness to improved mental well-being and reduced risks of chronic disease (36).
In the absence of a formal policy for physical activity and health in Puerto Rico’s Education Department, children may lack consistent opportunities, guidance and support to engage in regular physical activity, resulting in fragmented efforts across schools, communities and families. The results from this study could direct policy-makers and school administrative leaders to implement evidence-based physical activity and fitness interventions to prevent diseases associated with physical inactivity and poor fitness among children. Such interventions could prioritize active classroom programs, structured physical activity during recess and after-school fitness programs.
Strengths and limitations
The key strengths of this study include its longitudinal design, use of validated assessment tools, and objective measurement of physical activity through accelerometry. Some limitations need to be addressed, including the small sample size, which may mean that the study is underpowered for a small effect size (details about the power analysis are available as supplementary material), lack of food group analyses, geographical delimitation to the San Juan metropolitan area, and potential selection bias in recruiting voluntary participants, all of which limit the generalizability of the findings.
Conclusions
This longitudinal study provides critical insight into the health characteristics of children in elementary school in Puerto Rico, revealing persistently low levels of physical activity, high levels of sedentary time, increasing percentages of body fat over the 3 years and a consistent decline in meeting the Healthy Fitness Zone benchmarks. These trends were especially pronounced among girls, who consistently underperformed in assessments of muscular strength, endurance and body composition. Importantly, lower self-efficacy was associated with poorer fitness outcomes, highlighting the interconnected nature of physical and psychological health.
Despite adequate caloric intake, the likely imbalance between energy consumption and expenditure suggests a potential risk for developing obesity and related chronic conditions. These findings underscore the urgent need for early, targeted interventions that promote active lifestyles, improve nutritional habits and foster self-efficacy, particularly among young girls. Schools in Puerto Rico represent a vital setting for implementing interventions such as active recess programs, classroom-based activity breaks or walk-to-school programs. In the absence of formal policies for physical activity, evidence from this study can inform the development of school-based programs and public health strategies aimed at reversing these concerning trends and supporting healthier trajectories for Puerto Rican youth.
Acknowledgements.
The authors thank all of the graduate students from the master’s degree program in exercise sciences with a concentration in exercise physiology at the University of Puerto Rico’s Río Piedras Campus who assisted in the evaluations of physical activity and fitness. The authors also thank the school directors, teachers, parents and children who volunteered for the study.
Funding Statement
The study received institutional funding from the University of Puerto Rico, Río Piedras Campus.
Footnotes
Funding.
The study received institutional funding from the University of Puerto Rico, Río Piedras Campus.
Disclaimer.
Authors hold sole responsibility for the views expressed in the manuscript, which may not necessarily reflect the opinion or policy of the Revista Panamericana de Salud Pública/Pan American Journal of Public Health or the Pan American Health Organization.
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