Improvements in Physical Fitness are Associated with Favorable Changes in Blood Lipid Concentrations in Children.

Although accumulating evidence suggests the benefits of cardiorespiratory fitness and muscular fitness, little knowledge exists on how other physical fitness (PF) components are associated with cardiovascular disease (CVD) risk markers in children. Additionally, much of the relevant evidence is from longitudinal studies with CVD risk markers at a single time point (i.e., baseline) rather than changes in PF. The purpose of the present study was to examine whether initial 1-year changes in different performance measures of PF (i.e., endurance performance, muscular strength/endurance, flexibility, agility, and speed) can predict the subsequent changes (2-year change) in blood lipid concentrations in children. This 2-year longitudinal study included a total of 251 Japanese children (mean age 9.2 ± 0.4). PF tests were performed to comprehensively evaluate the participant's fitness levels (handgrip strength [upper body muscular strength], bent-leg sit-ups [muscular endurance], sit-and-reach [flexibility], side-step [agility], 20-meter shuttle run [endurance performance], 50-meter sprint [speed], standing long jump [lower body muscular strength], and softball throw [explosive arm strength and throwing ability]). Fasting lipid profile was assayed for triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and non-HDL-C concentration. Multilevel linear regressions were used to examine the associations between the preceding changes (over 1-year) in PF and subsequent changes (over 2-years) in blood lipid concentrations. We also examined the simultaneous associations between 2-year changes in PF and 2-year changes in blood lipid concentrations. For boys, preceding improvement in handgrip strength was negatively associated with TG concentration (ß = -0.260, p = 0.030); improvements in bent-leg sit-ups were negatively associated with clustered lipid scores (ß = -0.301, p = 0.038) and non-HDL-C (ß = -0.310, p = 0.044); and improvements in 50m sprinting were associated with subsequent changes in non-HDL-C (ß = 0.348, p = 0.006) and LDL-C (ß = 0.408, p = 0.001). For girls, improvements in handgrip strength was negatively associated with TG concentration (ß = -0.306, p = 0.017); and improvements in standing long jump were negatively associated with non-HDL-C (ß = -0.269, p = 0.021) and LDL-C (ß = -0.275, p = 0.019). For boys and girls, there were no significant simultaneous associations between 2-year changes in PF and 2-year changes in blood lipid concentrations. In conclusion, preceding change in physical fitness in relation to change in blood lipid concentration likely reflect a physiological adaptation to growth and maturation since these associations diminished in the subsequent year.

Classroom Standing Desks and Time-Series Variation in Sedentary Behavior and Physical Activity among Primary School Children.

The purpose of the present study was to examine the effects of height-adjustable standing desks on time-series variation in sedentary behavior (SB) among primary school children. Thirty-eight children aged 11-12 years (22 boys and 16 girls) from two classes at a primary school in Nagano, Japan, participated in this study. One class was allocated as the intervention group and provided with individual standing desks for 6 months, and the other was allocated as the control group. Time spent in SB, light-intensity physical activity (LPA), and moderate-to-vigorous-intensity physical activity (MVPA) was measured using accelerometers (ActiGraph) at baseline and follow-up. Time spent in SB was significantly lower by 18.3 min/day on average in the intervention class at follow-up (interaction effects: F(1, 36) = 4.95, p = 0.035, η2 = 0.082). This was accompanied by a significant increase in time spent in MVPA (+19.9 min/day on average). Our time-series analysis showed significant decreases in SB during school time, while no change in SB was found during non-school time. This result indicates that the use of standing desks promotes an overall reduction in SB with no compensatory increase during non-school time.