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Purpose: Young people spend a substantial proportion of their time at school sedentary; therefore, this setting represents an important target for interventions aimed at displacing sedentary time with physical activity. This study aimed to examine the postprandial metabolic effects of breaking sedentary time by accumulating walking and repeated bouts of nonambulatory standing during simulated school days in inactive adolescent girls., Methods: Seventeen girls (mean ± SD = 12.8 ± 0.4 yr) completed two 3-d experimental conditions. On days 1 and 2 of the standing + walking (STD-WLK) experimental trial, participants interrupted sedentary time by completing 4 × 10 min bouts of self-paced walking and accumulated 18 × 5 min standing bouts during each simulated school day. On day 3 of STD-WLK, participants attended school as normal with no additional physical activity or standing prescribed. On all 3 d of the control condition (CON), participants attended school as normal with no physical activity intervention. On days 2 and 3 of both STD-WLK and CON, a baseline capillary blood sample was provided to determine fasting [TAG] and [glucose]. Participants then consumed a standardized breakfast (0 h) and lunch (4.7 h), and blood samples were provided postprandially at 2.7, 5.3, and 7.3 h for [TAG] and [glucose]., Results: Energy expenditure was 28% (95% confidence interval = 8% to 52%) higher during school hours on day 1 and day 2 during STD-WLK compared with CON (2171 vs 1693 kJ; effect size = 0.89, P = 0.008). However, no reduction of fasting or postprandial [TAG] or [glucose] was observed on day 2 or day 3 ( P ≥ 0.245)., Conclusions: Two consecutive days of breaking prolonged sitting with self-paced walking and intermittent standing had no meaningful effect on postprandial metabolism in adolescent girls., (Copyright © 2022 by the American College of Sports Medicine.)

Introduction: This study examined the efficacy of maximal sprint running accumulated during a typical school day to modulate postprandial metabolism in adolescent boys., Methods: Nineteen adolescent boys completed three 2-d experimental conditions: a standard-practice control (CON), an accumulated in-school sprint running (ACC), and a single block of afterschool sprint running (BLO). On day 1, a fasting capillary blood sample was taken at 0735 h in the school. Three subsequent postprandial blood samples were taken at predetermined times after consumption of standardized breakfast and lunch. During ACC, participants accumulated four sets of 10 × 30-m maximal-intensity sprint runs across natural breaks in lessons. During BLO, participants performed the same number of sprints (40) in a single after-school exercise session. The blood samples from day 1 were replicated on the day after exercise (day 2)., Results: On day 1, no significant differences in total area under the plasma triacylglycerol concentration versus time curve (TAUC-TAG) were observed between conditions (P = 0.126). However, TAUC-insulin was lower in ACC compared with BLO (-26%, effect size [ES] = 0.86, P = 0.001) and CON (-22%, ES = 0.72, P = 0.010). On day 2, TAUC-TAG was 12% lower after ACC (ES = 0.49; P = 0.002) and 10% lower after BLO (ES = 0.37; P = 0.019) compared with CON. No significant differences were observed between conditions on day 2 for postprandial insulin or glucose (P ≥ 0.738)., Conclusion: Four sets of 10 × 30-m sprints, accumulated in four separate bouts (<5 min) during the school day, reduced postprandial triacylglycerol and insulin concentrations in adolescent boys and may represent an effective in-school exercise strategy to promote metabolic health.

Purpose: Although laboratory-based moderate- to high-intensity exercise reduces postprandial lipemia in adolescents, this exercise differs to the free-living physical activities in which young people typically engage. This study compared the effect of free-living afterschool soccer activity and treadmill exercise on in-school postprandial lipemia in adolescent boys., Methods: Fifteen boys (12.6 ± 0.5 yr) completed three, 2-d experimental trials. On day 1, participants rested (CON), exercised for 48 min on a treadmill at 60% V˙O2peak (TM), or played 48 min of 5-a-side soccer (SOC). On day 2, participants attended school where a capillary blood sample determined fasting triacylglycerol ([TAG]) and glucose ([glucose]) concentrations. Participants then consumed a standardized breakfast (0 h) and lunch (4.5 h), and blood samples were collected postprandially at 2.5, 5.0, and 7.0 h., Results: Reductions in fasting [TAG] were small-moderate after TM (-16%, 95% confidence interval [CI] = -27% to -2%, effect size [ES] = 0.46), but large after SOC (-30%, 95% CI = -40% to -20%, ES = 1.00) compared with CON; the concentration was also lower in SOC compared with TM (-18%, 95% CI = -29% to -5%, ES = 0.53). On the basis of ratios of geometric means, the area under the TAG versus time curve was 18% lower after TM (95% CI = -29% to -5%, ES = 0.51) and 25% lower after SOC (95% CI = -35% to -13%, ES = 0.76) compared with CON. By contrast, SOC and TM were not significantly different (-9%, 95% CI = -21% to 5%, ES = 0.25)., Conclusion: Compared with duration-matched inactivity (CON), after-school small-sided soccer (SOC) and treadmill exercise (TM) resulted in a similar, moderate reduction of postprandial lipemia in adolescent boys.

Purpose: This study aimed to investigate the absorption curve and acute effects of caffeine at rest in individuals with no spinal cord injury (SCI), paraplegia (PARA), and tetraplegia (TETRA)., Methods: Twenty-four healthy males (eight able-bodied [AB], eight PARA, and eight TETRA) consumed 3 mg·kg caffeine anhydrous (CAF) in a fasted state. Plasma caffeine [CAF], glucose, lactate, free fatty acid, and catecholamine concentrations were measured during a 150-min rest period., Results: Peak [CAF] was greater in TETRA (21.5 μM) compared with AB (12.2 μM) and PARA (15.1 μM), and mean peak [CAF] occurred at 70, 80, and 80 min, respectively. Moderate and large effect sizes were revealed for TETRA compared with PARA and AB (-0.55 and -1.14, respectively) for the total area under the [CAF] versus time curve. Large interindividual responses were apparent in SCI groups. The change in plasma catecholamine concentrations after CAF did not reach significance (P > 0.05); however, both adrenaline and noradrenaline concentrations were lowest in TETRA. Significant increases in free fatty acid were seen over time (P < 0.0005), but there was no significant influence of SCI level. Blood lactate concentration reduced over time (P = 0.022), whereas blood glucose concentration decreased modestly (P = 0.695), and no difference between groups was seen (P > 0.05)., Conclusion: The level of SCI influenced the caffeine absorption curve, and there was large interindividual variation within and between groups. Individual curves should be considered when using caffeine as an ergogenic aid in athletes with an SCI. The results indicate TETRA should trial low doses in training and PARA may consider consuming caffeine greater than 60 min before exercise performance. The study also supports caffeine's direct effect on adipose tissue, which is not secondary to catecholamine release.

Purpose: This study examined the potency of combining acute high-intensity exercise and energy intake restriction on postprandial triacylglycerol concentrations ([TAG]) in healthy girls., Methods: Sixteen 11- to 13-yr-old girls (mean (SD) body mass, 45.1 (7.6) kg; peak oxygen uptake (V˙O2), 43 (6) mL·kg(-1)·min(-1)) completed three 2-d conditions in a counterbalanced crossover design separated by 14 d. On day 1, participants completed 10 × 1-min interval runs (HIIR) or 5 × 1-min interval runs combined with 0.82 (0.19) MJ energy intake restriction (HIIR-ER) or rested (CON). Exercise was completed at 100% maximal aerobic speed determined from an incremental peak V˙O2 test, with 1-min recovery between intervals. On day 2, capillary blood samples were taken in the fasted state and at predetermined intervals throughout the 6.5-h postprandial period. A standardized breakfast and lunch were consumed immediately and 4 h after the fasting sample, respectively., Results: Based on ratios of the geometric means (95% confidence intervals (CI) for ratios), fasting [TAG] was 16% and 8% lower than CON in HIIR (-24% to -7%; effect size (ES), 0.49; P = 0.002) and HIIR-ER (-17% to 1%; ES, 0.24; P = 0.09), respectively; HIIR was 8% lower than HIIR-ER (-17% to 1%; ES, 0.25; P = 0.08). The total area under the [TAG] versus time curve was 10% and 9% lower than CON in HIIR (-16% to -3%; ES, 0.30; P = 0.01) and HIIR-ER (-15% to -2%; ES, 0.28; P = 0.01), respectively; HIIR-ER and HIIR were similar (-1%; -8% to 6%; P = 0.80)., Conclusions: Manipulations of HIIR and ER reduce postprandial [TAG] in girls. The magnitude of effect was marginally, although not meaningfully, greater after HIIR than that after HIIR-ER.

Purpose: This study aimed to examine the effect of 30 and 60 min of moderate-intensity treadmill walking on postprandial triacylglycerol concentrations ([TAG]) in healthy girls., Methods: Eighteen 10- to 14-yr-old girls (mean ± SD; body mass = 48 ± 11 kg, body fat = 19.0 ± 4.6%, peak oxygen uptake [V˙O2] = 47 ± 6 mL·kg·min) completed three 2-d trials in a counterbalanced crossover design, each separated by 14 d. On day 1, they rested (CON) or completed 30 min (EX30) or 60 min (EX60) of intermittent treadmill exercise at 56% peak V˙O2, inducing energy expenditures of 777 and 1536 kJ (186 and 367 kcal), respectively. On day 2, after a 12-h fast, a capillary blood sample was taken for fasting [TAG] before a high-fat milkshake (80 kJ·kg(-1) body mass) was consumed. Further blood samples were taken hourly over a 6-h postprandial rest period for [TAG]. ANOVA and Student's t-tests were used to analyze the data., Results: Fasting [TAG] was lower in EX60 than CON (95% confidence interval [CI] = -0.36 to 0.04, effect size (ES) = 0.41) and EX30 (95% CI = -0.47 to 0.04, ES = 0.46); all group mean concentrations were low (≤ 0.90 mmol·L(-1)). The main effect for condition revealed differences in postprandial [TAG] over time (ES = 0.36). The EX60 total area under the [TAG] versus time curve was lower than CON (95% CI = -2.66 to -0.04, ES 0.40) and EX30 (95% CI = -2.11 to 0.15, ES = 0.30); CON and EX30 were similar (95% CI = -1.44 to 0.71, ES = 0.10)., Conclusion: This study demonstrates that 60 min but not 30 min of moderate treadmill exercise, with a gross energy expenditure of 1536 kJ (367 kcal), attenuated postprandial [TAG] in girls.

Introduction: Acute moderate-intensity exercise reduces postprandial lipemia in boys. However, the effect of high-intensity exercise has not been investigated. This study examined the effect of low-volume, high-intensity interval running (HIIR) on postprandial plasma triacylglycerol (TAG) concentrations., Methods: Fifteen healthy, active boys (means ± SD; age = 11.8 ± 0.4 yr, body mass = 42.8 ± 8.0 kg, peak oxygen uptake [VO2] = 55 ± 6 mL · kg(-1) · min(-1)) completed two 2-d trials in a counterbalanced, crossover design separated by 14 d. On day 1, participants rested (CON) or completed 10 × 1 min running intervals at 100% maximal aerobic speed, determined from an incremental peak VO2 test, with 1 min recovery between intervals (HIIR). On day 2, capillary blood samples were taken in the fasted state and at predetermined intervals throughout the 6.5-h postprandial period while participants rested. A standardized breakfast was consumed at 0800 h, immediately after the fasting sample, and a standardized lunch meal was consumed at 1200 h., Results: Differences in fasting plasma TAG concentration were small to moderate (95% confidence interval [CI] = -0.11 to 0.01, effect size [ES] = 0.40). Postprandial TAG concentration was lower during HIIR compared with CON (95% CI = -0.19 to -0.02, ES = 0.58). The total area under the TAG concentration versus time curve was lower after HIIR compared with CON (5.2 ± 1.1 vs 5.8 ± 1.5 mmol(-1) · L 6.5 h; 95% CI = -1.18 to -0.12, ES = 0.50)., Conclusion: This is the first study to show that low-volume HIIR attenuates postprandial TAG concentration in healthy, active 11- to 12-yr-old boys.

Introduction: Acute exercise can reduce postprandial insulin concentrations and increase fat oxidation in adults, which may have important implications for insulin resistance and weight control. However, similar studies with young people or comparing overweight (OW) and nonoverweight (NO) individuals are sparse. Therefore, the acute effect of Fatmax exercise on glucose, insulin, and fat oxidation was examined in 12 OW and 15 NO girls., Methods: Participants completed two 2-d conditions in a counterbalanced order. On day 1, participants either expended 2.09 MJ (500 kcal) during treadmill exercise at individual Fatmax (EX) or 0.47 MJ (112 kcal) during rest (CON). On day 2, capillary blood and expired air samples were taken in the fasting state and at regular intervals for 2 h after high-glycemic-index breakfast consumption. Subsequently, blood glucose and plasma insulin concentrations were determined, and fat oxidation was estimated., Results: Blood glucose was similar between conditions in both groups (P > 0.05). Fasting plasma insulin (P = 0.047) and total area under the 2-h curve (P = 0.049) were reduced for EX compared with CON in the NO, but not OW girls (P > 0.05). Fasting fat oxidation was higher for EX than for CON in the NO girls (P = 0.036) and fat oxidation total area under the 2-h curve was higher for EX in both groups of girls (P ≤ 0.05)., Conclusions: A bout of Fatmax exercise performed ~16 h before high-glycemic-index breakfast consumption reduced fasting and postprandial insulin concentrations in NO girls and increased fat oxidation in both OW and NO girls. The higher postintervention energy and CHO intake in the OW compared with the NO girls or differences in metabolism between the two groups may have compromised potential exercise-induced reductions in insulin the OW girls.

Purpose: This study aimed to investigate the effects of fixed gear ratio wheel sizes on the physiological and biomechanical responses to submaximal wheelchair propulsion., Methods: Highly trained wheelchair basketball players (N = 13) propelled an adjustable sports wheelchair in three different wheel sizes (24, 25, and 26 inches) on a motor-driven treadmill. Each wheel was equipped with force-sensing hand-rims (SMARTWheel), which collected kinetic and temporal data. Oxygen uptake (V˙O2) and HR responses were measured with high-speed video footage collected to determine three-dimensional upper body joint kinematics., Results: Mean power output and work per cycle decreased progressively with increasing wheel size (P < 0.0005). Increasing wheel size also reduced the physiological demand with reductions in VO2 for 25-inch (0.90 ± 0.20 L · min(-1), P = 0.01) and 26-inch wheels (0.87 ± 0.16 L · min(-1), P = 0.001) compared with 24-inch wheels (0.98 ± 0.20 L · min(-1)). In addition, reductions in HR were observed for 26-inch wheels (99 ± 6 beats · min(-1)) compared with 25-inch (103 ± 8 beats · min(-1), P = 0.018) and 24-inch wheels (105 ± 9 beats · min(-1), P = 0.004). Mean resultant forces also decreased progressively with increasing wheel size (P < 0.0005). However, no changes in temporal or upper body joint kinematics existed between wheel sizes., Conclusions: A greater power requirement owing to a greater rolling resistance in 24-inch wheels increased the physiological demand and magnitude of force application during submaximal wheelchair propulsion.

Purpose: To examine the validity of perception-based intensity regulation during handcycling exercise., Methods: Eight spinal cord-injured (T11 incomplete to T4 complete) participants completed an incremental exercise test followed by a (.)VO2peak test using a sports hand bike. Subsequently, two 20-min exercise tests were completed at an individualized power output (PO) at moderate and vigorous intensities (50% and 70% of (.)VO2peak, respectively). On a separate occasion, participants were instructed to produce and maintain a workload equivalent to the average RPE for the 20-min imposed condition in a counterbalanced order. The (.)VO2 and blood lactate concentration [BLa(-)] were measured every 10 min, and HR and PO were measured at 1-min intervals., Results: There were no differences in average (.)VO2, percent V O2peak, HR, PO, and [BLa(-)] between the imposed PO conditions and RPE-regulated trials of either exercise intensity. Although PO increased slightly during the moderate-intensity RPE-regulated trial (P < 0.04), it remained relatively constant in the vigorous RPE-regulated trial. However, there was a tendency for PO to be slightly higher (P = 0.07) in the vigorous RPE-regulated trial., Conclusions: These data suggest that RPE is effective in controlling moderate and vigorous intensities throughout a 20-min handcycling exercise session for SCI participants.

Purpose: To compare the effects of 60-min bouts of intermittent moderate and vigorous exercise on postprandial plasma triacylglycerol (TAG) metabolism in eight healthy adolescent boys (mean +/- SD age: 13 +/- 0.3 yr)., Methods: Participants completed three conditions in a counterbalanced order. On day 1, they either rested for 110 min (CON), completed 6 x 10-min blocks of intermittent treadmill exercise at 53% peak V O2 (MOD), or 6 x 10-min blocks at 75% peak V O2 (VIG). On day 2 after a 12-h fast, a capillary blood sample was taken for [TAG] and [glucose] (mmol.L) and then a high-fat milkshake was consumed (1.50 g.kg fat, 1.22 g.kg CHO, and 0.22 g.kg protein; 80 kJ.kg). Further blood samples were taken every hour for a 6-h postprandial rest period for [TAG] and [glucose]., Results: Estimated energy expenditure was 45% higher in VIG than in MOD (95% confidence interval [CI] 23-72%). Fasting [TAG] and [glucose] did not differ between the conditions. Average [TAG] for the postprandial period was lower by 24% in MOD (95% CI -47% to 9%, P = 0.06) and by 21% in VIG (95% CI -42% to 8%, P = 0.08) than CON, with no meaningful difference (4%; 95% CI -27% to 48%, P = 0.50) between MOD and VIG. The total area under the [TAG] versus time curve (mmol.L 6 h) was lower by 24% in MOD (95% CI -42% to 0%, P = 0.05) and by 20% in VIG (95% CI -37% to 0%, P = 0.07) than CON. MOD and VIG were not different from each other (4%; 95% CI -18% to 32%, P = 0.54)., Conclusion: Both 60 min of moderate and vigorous intermittent exercises reduced postprandial [TAG]. However, the extra energy expended in the vigorous condition did not produce a dose-related reduction compared with the moderate-intensity condition.

Purpose: To examine the relative effectiveness of moderate-intensity continuous training and high-intensity interval training on pulmonary O2 uptake (VO2) kinetics at the onset of moderate- and severe-intensity cycle exercise in previously sedentary subjects., Methods: Twenty-three healthy subjects (11 males; mean +/- SD age 24 +/- 5 yr; VO2peak 34.3 +/- 5.5 mL x kg(-1) x min(-1)) were assigned to one of three groups: a continuous training group that completed three to four sessions per week of 30-min duration at 60% VO2peak (LO); an interval training group that completed three to four sessions per week involving 20 x 1-min exercise bouts at 90% VO2peak separated by 1-min rest periods (HI); or a control group (CON). Before and after the 6-wk intervention period, all subjects completed a series of step exercise tests to moderate and severe work rates during which pulmonary VO2 was measured breath-by-breath., Results: ANOVA revealed that continuous and interval training were similarly effective in reducing the phase II VO2 time constant during moderate (LO: from 31 +/- 8 to 23 +/- 5 s; HI: from 32 +/- 9 to 21 +/- 4 s; both P < 0.05; CON: from 30 +/- 6 to 29 +/- 7 s; NSD) and severe exercise (LO: from 35 +/- 6 to 24 +/- 7 s; HI: from 32 +/- 11 to 24 +/- 7 s; both P < 0.05; CON: from 27 +/- 7 to 25 +/- 5 s; NSD) and in reducing the amplitude of the VO2 slow component (LO: from 0.38 +/- 0.10 to 0.29 +/- 0.09 L x min(-1); HI: from 0.41 +/- 0.28 to 0.30 +/- 0.28 L x min(-1); both P < 0.05; CON: from 0.54 +/- 0.22 to 0.66 +/- 0.38 L.min; NSD)., Conclusions: Six weeks of low-intensity continuous training and high-intensity interval training were similarly effective in enhancing VO2 on-kinetics following step transitions to moderate and severe exercise in previously untrained subjects.

Purpose: To study the effect of exercise volume on pre- and early-pubertal children's lipid-lipoprotein profile., Methods: Thirty-four children (15 girls) completed 12 wk of exercise training, preceded by a 12-wk control period. Sixteen (7 girls and 9 boys) expended an additional 422 +/- 5 kJ.kg BM (LOW, 100 kcal.kg), whereas 18 (8 girls and 10 boys) expended an additional 586 +/- 7 kJ.g (MOD, 140 kcal.kg) as a result of the training program. They all exercised on three nonconsecutive days per week at 80 +/- 1% HRpeak. Exercise duration was individualized to match energy expenditure targets. Plasma TG, TC, and HDL-C were measured precontrol, pretraining, and posttraining. LDL-C, TC/HDL-C, and LDL-C/HDL-C were also calculated., Results: Group mean lipid-lipoprotein concentrations did not change as a result of training energy expenditure in either of the groups (P > 0.05). Dietary composition, habitual physical activity, and body composition were also relatively stable over the intervention period (P > 0.05). In the LOW, but not the MOD group, peak VO2 (mL.kg.min) tended to increase over the intervention period (P = 0.07). Pearson's product moment correlation analyses indicated that pretraining concentrations of TG, TC, LDL-C, TC/HDL-C, and LDL-C/HDL-C were all related to the small changes seen in the lipid-lipoprotein profile (P < 0.01)., Conclusion: Additional energy expenditure of 422 or 586 kJ.kg, as a direct result of aerobic exercise training over a 12-wk period, did not cause significant alterations in the lipid-lipoprotein profile in pre- and early-pubertal children. This may indicate that the exercise volume was insufficient, the lipoprotein profiles of the majority of children in this study were classified as "desirable," or more likely a combination of these factors.

Purpose: To examine the scaling behavior of peak oxygen uptake (VO2peak) in wheelchair athletes, adjusting for known covariates., Methods: Body mass, VO2peak, and an estimate of adiposity (sum of four skinfolds) were determined in a sample of 45 highly trained wheelchair basketball and racing athletes. The participants were classified as possessing either "high" or "low" trunk stability and balance using recognized sporting classifications. A wheelchair ergometer was used to obtain the VO2peak measurements. The relationship between VO2peak and body mass was obtained via a nonlinear allometric model with the sum of four skinfolds, trunk stability and balance, and chronological age entered as covariates., Results: The point estimate exponent for body mass was 0.82 (95% CI, 0.54-1.10). After controlling for the influence of body mass, adiposity, and age, the wheelchair athletes with greater trunk stability and balance had on average an 11% greater VO2peak. The regression model explained 54% of the sample variance in VO2peak., Conclusions: The obtained mass exponent of 0.82 is congruent with that predicted from the multiple-causes allometric cascade model and consideration of the physiological characteristics of spinal cord injured athletes. To compare the body size-independent VO2peak values of athletes within the study sample, the mass exponent of 0.82 may be adopted (i.e., mL x kg(-0.82) x min(-1)). The uncertainty in the point estimate, reflected in the relatively wide 95% CI, highlights the need for further research with larger samples to increase the precision of estimation.

Purpose: To examine the relationship between competitive 800-m and 1500-m performance times and a number of physiological variables in a group of endurance-trained, adolescent runners., Methods: Twenty-three boys and 17 girls volunteered to participate in the study. Track-based, running performance times were available for 18 boys and 14 girls for the 800 m, and 16 boys and 13 girls for the 1500 m. The relationships between these times and the following physiological variables were determined: peak VO(2) running economy (RE), estimated running speed at peak vV0(2peak), peak and mean anaerobic power, and fixed [BLa ] at 2.0, 2.5, and 4.0 mmol.L., Results: RE and vV0(2peak) were significant independent variables for the boys' 800 m (r = 0.62 and -0.62, < 0.01). For the girls, once chronological age was partialled out, none of the measured variables were significantly related to 800-m performance. For the 1500-m event, peak V0(2), vV0(2peak), and the running speed at 2.5 mmol.L (v2.5) were significant independent variables in the boys (r = -0.43, -0.39, and -0.53, < 0.05) and girls (r = -0.50, -0.61, and -0.54, < 0.05). In addition, the V0(2) at 2.5 mmol.L V0(2) (2.5) was related to the 1500-m time in the girls (r = -0.54, < 0.05)., Conclusion: The physiological variables that were most strongly correlated with middle-distance running performance were v2.5 and the vV0(2peak). To a lesser extent peak V02 may also play a role although it is understood that its contribution may be accounted by vV0(2 peak).

Purpose: The purpose of this study was to investigate whether a sample of 9- to 12-yr-old children fulfilled existing U.S. and UK physical activity recommendations for health., Methods: Habitual physical activity levels of 79 pre- and early pubertal children were assessed using continuous heart rate monitoring over a period of 4 d. Mean, daily, cumulative physical activity levels spent above heart rate thresholds were compared with U.S. and UK recommended values., Results: In this study, when cumulative amounts of physical activity were considered, at intensities greater than 120 beats x min(-1) and 75% above resting heart rate, pre- and early pubertal British children appear to engage in sufficient physical activity to meet U.S. and UK minimum daily recommendations., Conclusions: Interpretations of children's physical activity levels depend on thresholds set for intensity of physical activity and whether cumulative or continuous bouts of activity are included in the analysis.

Purpose: It is still unclear how habitual physical activity (HPA), peak VO2, percent body fat (%BF), and dietary composition are related to the lipid-lipoprotein profile in children. The purpose of this study was to identify independent contributions from these selected predictor variables to prepubertal children's lipid-lipoprotein profile., Methods: Peak VO2, HPA from continuous heart rate monitoring, %BF, 7-d dietary analysis, total cholesterol (TC), total triacylglycerol (TG), high density lipoprotein (HDL) cholesterol (HDL-C), low density lipoprotein (LDL) cholesterol (LDL-C), TC/HDL-C, and LDL-C/HDL-C were determined in 33 prepubertal girls and 38 prepubertal boys (mean +/- SD age, 10.6 +/- 0.7 yr)., Results: Bivariate correlation analyses revealed that peak VO2, %BF, and HPA were related to the lipid-lipoprotein profile in girls (P < 0.05). For the boys, HPA was only related to TC/HDL-C (P < 0.05) and LDL-C/HDL-C (P < 0.05), whereas daily energy intake (kJ x d(-1)) was associated with TC and LDL-C (P < 0.05). Multiple linear regression analyses indicated that peak VO2, %BF and HPA were the main predictor variables for the girls. Peak VO2 accounted for 22.7%, 24.8%, 22.5%, and 24.2% of the unique variance (sr(i)2) in TG, HDL-C, LDL-C/HDL-C, and TC/HDL-C, respectively. For TC and LDL-C in girls, sr(i)2 were 18.0% and 22.6%, respectively, from HPA. In contrast, only daily energy intake had a significant unique contribution to the variance of TC (15.4%) and LDL-C (22.0%) for the boys., Summary: The main findings from this study were that the predictor variables are lipid-lipoprotein specific and depend on gender. These results would support the growing evidence that it is important to nurture an active lifestyle in children from an early age and that an awareness of fitness and body fatness is required.

Purpose: This study examined the effect of exercise training on prepubertal children's (ET, N = 28) lipid-lipoprotein profile, relative to a maturity matched control group (CON, N = 20)., Methods: Training for ET involved stationary cycling for 30 min, 3 times.wk-1 for 12 wk, at 79.3 +/- 1.2% (mean +/- SD) peak heart rate (HR). Controls maintained their usual lifestyle pattern. Plasma concentrations of total triacylglycerol (TG), total cholesterol (TC), and high-density lipoprotein (HDL)-cholesterol (HDL-C) were determined pre- and postintervention. Low-density lipoprotein (LDL)- cholesterol (LDL-C) was subsequently estimated from these concentrations, and the ratios TC/HDL-C and LDL-C/HDL-C were also calculated. There were no pretest differences (P > 0.05) for any of these blood analytes between groups. The following, potentially, confounding variables were also measured: peak VO2, percent body fat (%BF), dietary composition, and habitual physical activity. These variables, with pretest HDL-C, were included as covariates in two-way split plot ANCOVA analyses. Dietary variables were not included as covariates as they were not related to any of the blood analytes., Results: There were no differences over time or between groups for TG and TC (P > 0.05). LDL-C decreased in ET (-10.2%) but remained unchanged in CON (0.3%) over the intervention period (P < 0.05). HDL-C increased in ET (9.3%) but decreased in CON (-8.9%) (P < 0.01). A similar, but inverted, pattern of change (P < 0.01) was revealed for both ratios, TC/HDL-C (-11.6% vs 6.3%, ET and CON, respectively), and LDL-C/HDL-C (-17.2% vs 8.0%, ET and CON, respectively). The favorable alterations in the lipid-lipoprotein profile for ET were independent of alterations in peak VO2 (group x time interaction, P < 0.05), %BF (main effect time, P < 0.01), and habitual physical activity (group x time interaction, P < 0.01)., Conclusions: In conclusion, the favorable alterations in the lipoprotein profile seen in this study would suggest that it is possible to influence the prepubertal lipoprotein profile independent of alterations in confounding variables such as body composition, cardiorespiratory fitness, and habitual physical activity.