Browse

Background: This study investigates the association between television (TV) viewing and child adiposity and if parental education and child ethnicity moderate this association. Method: Cross-sectional, pooled (2013/2014–2016/2017) adult and child New Zealand Health Survey were matched resulting in 13,039 children (2–14 y) and parent dyads. Child TV viewing was estimated using self-reported time for each weekday and weekend. The height (in centimeters), weight (in kilograms), and waist circumference of parents and children were measured. Childhood body mass index and obesity were defined using the International Obesity Task Force cutoff values. Effect modification was assessed by interaction and then by stratifying regression analyses by parent education (low, moderate, and high) and child ethnicity (Asian, European/other, Māori, and Pacific). Results: Overall, watching ≥2 hours TV on average per day in the past week, relative to <2 hours TV viewing, was associated with a higher odds of obesity (adjusted odds ratio = 1.291 [1.108–1.538]), higher body mass index z score (b = 0.123 [0.061–0.187]), and higher waist circumference (b = 0.546 [0.001–1.092]). Interactions considering this association by child ethnicity and parent education revealed little evidence of effect modification. Conclusion: While TV viewing was associated with child adiposity, the authors found little support for a moderating role of parental education and child ethnicity.

Background: Green schoolyard renovations lead to immediate positive changes in moderate to vigorous physical activity (MVPA) and social behavior. This pilot study examines whether these benefits are equally distributed across gender and age and maintained 16 months postgreening. Methods: Physical activity and social interactions during recess were recorded at control (n = 389) and experimental (n = 642) Title I urban elementary schools with direct observation and accelerometers. Results: Activity profiles were similar to 4-month postgreening and to baseline for experimental girls and boys, respectively. There was no difference in MVPA minutes between sexes (girls = 11.8; 95% confidence interval [CI], 11.1 to 12.5]; boys = 12.8; 95% CI, 12.0 to 13.4) and no difference in sitting minutes between age groups (first to fourth = 2.0; 95% CI, 1.5 to 2.6; fifth to sixth = 1.8; 95% CI, 1.1 to 2.4) in green areas. Experimental students spent more time in MVPA (11.2 min; 95% CI, 10.6 to 11.8 vs 8.9 min; 95% CI, 8.3 to 9.3), in small groups (10.6 min; 95% CI, 10.2 to 11.0 vs 9.2 min; 95% CI, 8.5 to 9.9), and engaged in more prosocial interactions (5.5; 95% CI, 5.1 to 6.3 vs 3.7; 95% CI, 3.0 to 4.2) than control students. Conclusions: Green schoolyard renovations result in persistent changes to recess behavior that are characteristic of a more collaborative community and counteract age-related declines in MVPA, particularly for girls.

Purpose: This study aimecd to investigate whether elite athletes could reach higher values of maximal oxygen uptake ($\dot{\mathrm{V}}{\mathrm{O}}_2\text{max}$) during a decremental exercise test in comparison with a traditional incremental test, as recently demonstrated in trained individuals. Methods: Nine male runners (age 25.8 [5.1] y, season best 10-km time 31:19 [1:50]) performed, on different days, 3 maximal uphill (5% grade) running exercise tests in fixed order: an incremental test (INC₁), a V-shape exercise test (where speed started at 0.5 km·h⁻¹ higher than the top stage finished during INC₁ and was slowly decreased during 5.5 min, when it was again increased in similar fashion to the INC tests), and a final incremental test (INC₂). Results: $\dot{\mathrm{V}}{\mathrm{O}}_2\text{max}$ during the V-shape exercise test was higher than during INC₁ (6.3% [3.0%], P = .01), although running speed was lower (16.6 [1.7] vs 17.9 [1.6] km·h⁻¹, P = .01). Performance was similar between INC₁ and INC₂, but $\dot{\mathrm{V}}{\mathrm{O}}_2\text{max}$ during INC₂ was higher than INC₁ (P < .001). During the V-shape exercise test, 5 participants reached the incremental part of the test, but $\dot{\mathrm{V}}{\mathrm{O}}_2$ did not increase ($\mathrm{\Delta }\dot{\mathrm{V}}{\mathrm{O}}_2=52\hspace{0.17em}[259]\mathrm{mL}·{\text{min}}^{-1}$, P = .67), despite higher running speed (approximately 1.1 km·h⁻¹, P < .01). Heart rate, pulmonary ventilation, breathing rate, and respiratory exchange ratio measured at $\dot{\mathrm{V}}{\mathrm{O}}_2\text{max}$ were not different between tests. Conclusion: A decremental exercise test of sufficient intensity can produce higher $\dot{\mathrm{V}}{\mathrm{O}}_2\text{max}$ than a traditional incremental test, even in elite athletes, and this is maintained during a subsequent incremental test.

Purpose: To investigate the effects of caffeine (CAF) on performance during high- and long-jump competitions. Methods: Using a crossover and double-blind design, 6 well-trained high jumpers and 6 well-trained long jumpers performed a simulation of a high- and long-jump competition 60 minutes after ingesting a capsule containing either 5 mg·kg⁻¹ body mass of anhydrous CAF or a placebo. The high jumps were video recorded for kinematic analysis. The velocity during the approach run of the long jump was also monitored using photocells. Results: CAF improved jump performance (ie, the highest bar height overlap increased by 5.1% [2.3%], P = .008), as well as enhancing the height displacement of the central body mass (+1.3% [1.7%], P = .004) compared with the placebo. CAF had no ergogenic effect on jump distance (P = .722); however, CAF increased the velocity during the last 10 m of the long jump (P = .019), and the percentage of “foul jumps” was higher than that expected by chance in the CAF group (80.5% [12.5%], χ² = 13.44, P < .001) but not in the cellulose condition (58.3% [22.9%], χ² = 1.48, P = .224). Conclusion: CAF ingestion (5 mg·kg⁻¹ body mass) improves high-jump performance but seems to negatively influence technical aspects during the approach run of the long jump, resulting in no improvement in long-jump performance. Thus, CAF can be useful for jumpers, but the specificity of the jump competition must be taken into account.