Cardiorespiratory Fitness as a Mediator of the Association between Physical Activity and Overweight and Obesity in Adolescent Girls

Reliability of field- and laboratory-based assessments of health-related fitness in preschool-aged children

OBJECTIVES

Reliable measurements of health-related fitness-cardiorespiratory endurance, muscular endurance, muscular strength, body composition, and flexibility-are imperative for understanding and tracking health-related fitness from the preschool age. This study aimed to examine the test-retest reliability of field-based (i.e., sit and reach [standard and back-saver], standing long jump, grip strength); and laboratory-based (i.e., Bruce Protocol Treadmill Test, Wingate Anaerobic Test) assessments of health-related fitness in preschool aged children (4-5 years).

METHODS

Forty-two typically developing children participated in both assessment time points separated by 2-3 weeks. All fitness assessments were administered individually and repeated in the same order by the same assessor. Heteroscedasticity was examined for each parameter. Intraclass correlation coefficients were calculated to assess test-retest reliability.

RESULTS

All parameters were homoscedastic. Test-retest reliability for the field-based tests and Bruce Protocol Treadmill Test parameters were moderate to good. Test-retest reliability for the Wingate Test parameters were good to excellent for maximum pedal rate, peak power, and peak power/kg; mean power and fatigue measured at 10 and 30 s demonstrated moderate to excellent test-retest reliability.

CONCLUSION

The standard sit and reach, grip strength, and short-term muscle power from the Wingate test are reliable assessments of health-related fitness in preschool-aged children.

Perceived Physical Literacy Is Associated with Cardiorespiratory Fitness, Body Composition and Physical Activity Levels in Secondary School Students

BACKGROUND

Overweight and obese adolescents are often associated with lower Physical Activity (PA) levels and low Cardiorespiratory Fitness (CRF). Recently, the concept of Physical Literacy (PL), has been suggested to be associated with higher levels of active behavior and better health in adolescents. The purpose of this study is to investigate the relationships between PL, body composition, cardiorespiratory fitness and physical activity levels in French secondary school students.

METHODS

The level of PL was assessed in 85 French adolescents using a French version of the Perceived Physical Literacy Instrument (F-PPLI). Cardiorespiratory fitness was measured by the "20 m adapted walk/shuttle run test". The PA level was assessed by the Youth Risk Behavior Surveillance System questionnaire. Weight status was measured by the Body Mass Index (BMI) and the body composition data.

RESULTS

We find a significant association between the PL and the percentage Fat Mass (%FM) (r = -0.43; p ≤ 0.01), between the PL and moderate to vigorous PA (MVPA) per week (r = 0.38; p ≤ 0.01). The PL was associated (r = 0.36; p ≤ 0.01) with the percentage of Skeletal Muscle Mass (%SMM) and cardiorespiratory fitness (r = 0.40; p ≤ 0.05).

CONCLUSIONS

Developing the PL for the most disadvantaged secondary school students in a PA program could be a suitable strategy to increase their PA level, reduce their adiposity, and promote better long-term health.

Effects of running-based versus body-weight-based high-intensity interval training on physical fitness in healthy adolescents

Objectives: High-intensity interval training improves aerobic endurance, but the effectiveness of different training protocols is unclear. This study compared the effects of running-based high-intensity interval training (R-HIIT) and body weight-based high-intensity interval training (B-HIIT) on physical fitness in adolescents. Methods: This was a pre-and post-test quasi-experimental design in which a seventh-grade natural class was randomly selected from three homogeneous middle schools, and then the three natural classes were randomly divided into three groups: the R-HIIT group (n = 54), the B-HIIT group (n = 55), and the control group (Con, n = 57). Both intervention groups exercised twice a week for 12 weeks with a 2:1 (1 min:30 s) load-interval ratio and exercise intensity controlled at 70%-85% maximum heart rate. R-HIIT was in the form of running, and B-HIIT was in the form of resistance exercises using the participants' body weight. The control group was instructed to continue their normal behavior. cardiorespiratory fitness, muscle strength and endurance, and speed were measured before and after the intervention. Statistical differences between and within groups were determined using repeated measures analysis of variance. Results: Compared to the baseline, both the R-HIIT and B-HIIT intervention groups significantly improved CRF, muscle strength, and speed (p < 0.05). The B-HIIT group was significantly better than R-HIIT in improving CRF (4.48 mL/kg/min vs 3.34 mL/kg/min, p < 0.05), and only the B-HIIT improved sit-up muscle endurance (ηp 2 = 0.30, p < 0.05). Conclusion: The B-HIIT protocol was significantly more effective than the R-HIIT protocol in developing CRF and improving muscle health indicators.

Cardiorespiratory Fitness, Obesity and Physical Activity in Schoolchildren: The Effect of Mediation

There are only a few studies that have examined the interaction between physical activity (PA), cardiorespiratory fitness (CRF), and overweightness/obesity in adolescents, and these studies have shown some limitations. The objective of this study was to examine whether the association between PA (moderate-vigorous PA [MVPA], moderate PA [MPA], and vigorous PA [VPA]) and obesity is mediated by CRF. This cross-sectional study was conducted in six middle and high-schools in the Porto district (Portugal), comprising 632 children and adolescents. Fat mass (FM), CRF, MVPA, MPA, and VPA were assessed. The Process macro for SPSS was used. CRF was significantly associated with PA for both children and adolescents. Likewise, FM was negatively and significantly associated with CRF for both children (β = -0.337) and adolescents (β = -0.255). FM was associated with PA in children (MVPA: β = -0.102; MPA: β = -0.118; VPA: β = -0.305) and adolescents (MVPA: β: -0.103; MPA: β = -0.082; VPA: β = -0.204). The mediation analysis showed that the association between PA (MVPA//MPA/VPA) and obesity was mediated by CRF, in both children and adolescents, with a significant value in the Sobel test. Obesity is associated with CRF and MVPA, MPA, and VPA. However, CRF acted as a complete mediator between the association of obesity and PA.

Effect modification of cardiorespiratory fitness, obesity, and physical activity in adults

We investigated if cardiorespiratory fitness modifies the association between obesity and the level of physical activity. In this cross-sectional study, we analyzed data from 746 adults, free of diagnosed cardiorespiratory or locomotor diseases. We analyzed sociodemographic and clinical information, cardiovascular risk factors, cardiorespiratory fitness, anthropometry, and level of physical activity (time spent in moderate-to-vigorous physical activity). Those that spent more time in moderate-to-vigorous physical activity were younger, male, with lower body mass index, without self-reported arterial blood hypertension, diabetes and dyslipidemia, non-smokers, and presented with better cardiorespiratory fitness. The linear regression coefficients showed that cardiorespiratory fitness changes according to the level of physical activity and body mass index (obesity in low cardiorespiratory fitness: β 6.0, p = 0.213, 95%CI -3.5 to 15.6; in intermediate cardiorespiratory fitness: β 6.3, p = 0.114, 95%CI -1.5 to 14.2; in high cardiorespiratory fitness: β -6.3, p = 0.304, 95%CI -18.4 to 5.8). This effect modification trend was present after adjusting the model by covariates. Cardiorespiratory fitness potentially modifies the association between body mass index and the level of physical activity. It should be routinely assessed to identify persons with overweight/ obesity with low/ intermediate cardiorespiratory fitness to prescribe individualized training.