Laura A. Barrett

Postprandial Triacylglycerol in Adolescent Boys: A Case for Moderate Exercise

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.

Acute High-Intensity Interval Running Reduces Postprandial Lipemia in Boys

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.

Effect of repeated sprints on postprandial endothelial function and triacylglycerol concentrations in adolescent boys

Abstract This study investigated whether repeated, very short duration sprints influenced endothelial function (indicated by flow-mediated dilation) and triacylglycerol concentrations following the ingestion of high-fat meals in adolescent boys. Nine adolescent boys completed two, 2-day main trials (control and exercise), in a counter-balanced, cross-over design. Participants were inactive on day 1 of the control trial but completed 40 × 6 s maximal cycle sprints on day 1 of the exercise trial. On day 2, capillary blood samples were collected and flow-mediated dilation measured prior to, and following, ingestion of a high-fat breakfast and lunch. Fasting flow-mediated dilation and plasma triacylglycerol concentration were similar in the control and exercise trial (P > 0.05). In the control trial, flow-mediated dilation was reduced by 20% and 27% following the high-fat breakfast and lunch; following exercise these reductions were negated (main effect trial, P < 0.05; interaction effect trial × time, P < 0.05). The total area under the plasma triacylglycerol concentration versus time curve was 13% lower on day 2 in the exercise trial compared to the control trial (8.65 (0.97) vs. 9.92 (1.16) mmol · l−1 · 6.5 h, P < 0.05). These results demonstrate that repeated 6 s maximal cycle sprints can have beneficial effects on postprandial endothelial function and triacylglycerol concentrations in adolescent boys.

Effect of exercise on postprandial endothelial function in adolescent boys.

The ingestion of high-fat meals induces a state of endothelial dysfunction in adults. This dysfunction is attenuated by prior exercise. The response of young people to these nutritional and physiological stressors has not been established. Thus, the purpose of the present study was to investigate if a bout of moderate-intensity exercise influenced endothelial function (as indicated by flow-mediated dilation (FMD)) following the ingestion of a high-fat breakfast and lunch in adolescent boys (aged 12·6-14·3 years). Two, 2 d main trials (control and exercise) were completed by thirteen adolescent boys in a counter-balanced, cross-over design. Participants were inactive on day 1 of the control trial, but completed 60 min of walking at 60 % peak oxygen uptake in the exercise trial. On day 2, endothelial function was assessed via FMD prior to, and following, ingestion of a high-fat breakfast and lunch. There was no difference in fasting FMD between the control and exercise trial (P= 0·449). In the control trial, FMD was reduced by 32 % following consumption of the high-fat breakfast and by 24 % following lunch. In the exercise trial, the corresponding reductions were 6 and 10 %, respectively (main effect trial, P= 0·002). These results demonstrate that moderate-intensity exercise can attenuate the decline in FMD seen following the consumption of high-fat meals in adolescent boys.

A Multi-Channel Opto-Electronic Sensor to Accurately Monitor Heart Rate against Motion Artefact during Exercise

This study presents the use of a multi-channel opto-electronic sensor (OEPS) to effectively monitor critical physiological parameters whilst preventing motion artefact as increasingly demanded by personal healthcare. The aim of this work was to study how to capture the heart rate (HR) efficiently through a well-constructed OEPS and a 3-axis accelerometer with wireless communication. A protocol was designed to incorporate sitting, standing, walking, running and cycling. The datasets collected from these activities were processed to elaborate sport physiological effects. t-test, Bland-Altman Agreement (BAA), and correlation to evaluate the performance of the OEPS were used against Polar and Mio-Alpha HR monitors. No differences in the HR were found between OEPS, and either Polar or Mio-Alpha (both p > 0.05); a strong correlation was found between Polar and OEPS (r: 0.96, p < 0.001); the bias of BAA 0.85 bpm, the standard deviation (SD) 9.20 bpm, and the limits of agreement (LOA) from −17.18 bpm to +18.88 bpm. For the Mio-Alpha and OEPS, a strong correlation was found (r: 0.96, p < 0.001); the bias of BAA 1.63 bpm, SD 8.62 bpm, LOA from −15.27 bpm to +18.58 bpm. These results demonstrate the OEPS to be capable of carrying out real time and remote monitoring of heart rate.

Acute Exercise and Postprandial Lipemia in Young People

Exaggerated postprandial triacylglycerol concentrations (TAG) independently predict future cardiovascular events. Acute exercise and diet interventions attenuate postprandial TAG in adults. This paper aims to examine the exercise postprandial lipemia studies published to date in young people. Nine studies satisfied the inclusion criteria adopted for this summary. The majority of studies are in boys (22% girls) and have shown a single ~60-min session of moderate-intensity exercise, performed 12-18 hours before a standardized meal, reduces postprandial TAG. Manipulations of exercise duration and intensity suggest an exercise energy expenditure dose-dependent response is not supported directly in healthy young people. Studies investigating alternative exercise bouts have reported lower postprandial TAG after simulated intermittent games activity, high-intensity interval running and cumulative 10-min blocks over several hours, which may appeal to the spontaneous physical activity habits of young people. Although extension of these initial findings is warranted, exercise may be an effective strategy to promote regular benefits in TAG metabolism in children and adolescents; this may contribute to an improved cardiovascular disease risk profile early in life.

Exercise energy expenditure and postprandial lipemia in girls

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 Students 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.

High-Intensity Running and Energy Restriction Reduce Postprandial Lipemia in Girls.

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.

Acute Effects of Energy Deficit Induced by Moderate-Intensity Exercise or Energy-Intake Restriction on Postprandial Lipemia in Healthy Girls

Eleven healthy girls (mean ± SD: age 12.1 ± 0.6 years) completed three 2-day conditions in a counterbalanced, crossover design. On day 1, participants either walked at 60 (2)% peak oxygen uptake (energy deficit 1.55[0.20] MJ), restricted food energy intake (energy deficit 1.51[0.25] MJ) or rested. On day 2, capillary blood samples were taken at predetermined intervals throughout the 6.5 hr postprandial period before, and following, the ingestion of standardized breakfast and lunch meals. Fasting plasma triacylglycerol concentrations (TAG) was 29% and 13% lower than rest control in moderate-intensity exercise (effect size [ES] = 1.39, p = .01) and energy-intake restriction (ES = 0.57, p = .02) respectively; moderate-intensity exercise was 19% lower than energy-intake restriction (ES = 0.82, p = .06). The moderate-intensity exercise total area under the TAG versus time curve was 21% and 13% lower than rest control (ES = 0.71, p = .004) and energy-intake restriction (ES = 0.39, p = .06) respectively; energy-intake restriction was marginally lower than rest control (-10%; ES = 0.32, p = .12). An exercise-induced energy deficit elicited a greater reduction in fasting plasma TAG with a trend for a larger attenuation in postprandial plasma TAG than an isoenergetic diet-induced energy deficit in healthy girls.

The accumulation of exercise and postprandial endothelial function in boys

The purpose of this study was to investigate the effect of accumulating 60 min of exercise on endothelial function and triacylglycerol concentrations following the ingestion of a high‐fat breakfast and lunch in 14 adolescent boys (aged 12 to 14 years). Two, 2‐day main trials (control and exercise) were completed in a counter‐balanced, cross‐over design. Participants were inactive on day 1 of the control trial but on day 1 of the exercise trial completed 6 × 10 min runs at 70% of peak oxygen uptake, spread over the day. On day 2, triacylglycerol concentrations and flow‐mediated dilation (FMD) were measured prior to, and following, ingestion of the high‐fat meals. In the control trial, FMD was reduced by 30% and 33% (P < 0.001) following the high‐fat breakfast and lunch; following exercise these reductions were negated (main effect trial, P = 0.002, interaction effect trial × time, P < 0.001). The total and incremental areas under the triacylglycerol concentration vs time curve were reduced by 11% and 16% in the exercise trial; however, these differences were not significant (P > 0.05). These results support the concept of accumulating physical activity for health in adolescents as the accumulated exercise attenuated the decline in FMD seen following the consumption of high‐fat meals.