Metabolism and exercise during youth

Metabolism and exercise during yout

High-intensity interval training

High-intensity interval training (HIIT) is characterised by brief, intermittent bursts of near- or maximal-intensity exercise, interspersed by periods of active or passive recovery. The limited available evidence suggests that HIIT is an efficacious training method for young athletes. The effect of HIIT on cardiorespiratory fitness (CRF), endurance performance, explosive strength and sport-specific performance has been examined in a range of young athletic populations from various sports. Furthermore, promising preliminary findings suggest that HIIT may confer further benefits to a range of health outcome measures including fasting insulin, lipoproteins, systolic blood pressure and endothelial function; obese youth may benefit particularly from this type of training. Improved cardiorespiratory fitness has been observed consistently after HIIT in athletic and non-athletic populations. Larger studies, extended over longer periods, that include valid measures of exercise compliance, tolerance and enjoyment are required to further delineate the priority that could be afforded to this type of training

Mixed active and passive, heart rate-controlled heat acclimation is effective for Paralympic and able-bodied triathletes

Purpose To explore the effectiveness of mixed, active and passive heat acclimation (HA), controlling the relative intensity of exercise by heart rate (HR) in paratriathletes (PARA) and determine adaptation differences to able-bodied (AB) triathletes.Methods Seven elite paratriathletes and thirteen AB triathletes undertook an 8-d HA intervention consisting of five HR-controlled sessions and three passive heat exposures (35oC, 63% relative humidity). On the first and last day of HA, heat stress tests were conducted whereby thermoregulatory changes were recorded during at a fixed, submaximal workload. The AB group undertook 20 km cycling time trials pre- and post-HA with performance compared to an AB, non-acclimated control group.Results During the heat stress test, HA lowered core temperature (PARA: 0.27 ± 0.32oC; AB: 0.28 ± 0.34oC), blood lactate concentration (PARA: 0.23 ± 0.15 mmol∙l-1; AB: 0.38 ± 0.31 mmol∙l-1) with concomitant plasma volume expansion (PARA: 12.7 ± 10.6; AB: 6.2 ± 7.7%) (p≤0.047). In the AB group, a lower skin temperature (0.19 ± 0.44oC) and HR (5 ± 6 bpm) with a greater sweat rate (0.17 ± 0.25 l∙h-1) was evident post-HA (p≤0.045) but this was not present for the PARA group (p≥0.177). The AB group improved their performance by an extent greater than the smallest worthwhile change based on the normal variation present with no HA (4.5 vs. 3.7%).Conclusions Paratriathletes are capable of displaying partial HA, albeit not to same extent as AB triathletes. The HA protocol was effective at stimulating thermoregulatory adaptations with performance changes noted in AB triathletes.</div

Carbohydrate needs of the young athlete

Carbohydrate (CHO) typically provides the majority of energy in the athlete’s diet and is essential to fuel high intensity exercise. Ensuring adequate energy is available to meet the demands of high energy expenditures is important in the young athlete to ensure proper growth, development, and maturation. Physiological and metabolic changes that accompany the transition from childhood to adolescence and to adulthood, combined with the additional energy expenditure arising from exercise, mean that the dietary needs of young athletes require special consideration. However, in contrast to the well-documented literature in adults, little research attention has been given to child and adolescent populations. Thus, the development of specific recommendations for CHO intake in young athletes is difficult. Nevertheless, it is possible to make some general recommendations. Both the total daily CHO intake and the timing of CHO consumption in relation to exercise can determine whether adequate CHO substrate is available for muscles and the central nervous system or whether CHO fuel sources might limit exercise performance. In terms of the overall diet, CHO should contribute to the majority of energy intake, which must be high enough to support growth and maturation whilst fuelling the additional physical activity, and consequently elevated energy expenditure, in young athletes. In particular, CHO is an important fuel for high intensity exercise in young athletes. Decrements in exercise performance, fatigue and changes in body composition may serve as useful indicators that CHO intake may not be adequate, particularly in female adolescent athletes. During exercise, drinks containing CHO could be considered for young athletes engaged in endurance exercise due to the preferential use of exogenous CHO in younger athletes in the pre- or early- pubertal stages. However, evidence on CHO loading and CHO for post-exercise recovery does not appear to be available in children or adolescents. This chapter provides an overview of the available evidence that can be used to inform recommendations for CHO intake and timing in young athletes. Where no direct evidence in young athletes is available, we have relied on the relevant adult-based literature whilst emphasising that the direct translation and application of these findings to children and adolescents must be viewed cautiously

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

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 concentrations [TAG]. METHODS: Fifteen healthy, active boys (means(SD): age 11.8(0.4) years; body mass 42.8(8.0) kg; peak oxygen uptake (V ̇2) 55(6) mL·kg·min) completed two, 2-day trials in a counter-balanced, cross-over design separated by 14 days. On day 1, participants rested (CON) or completed 10 x 1 min running intervals at 100% maximal aerobic speed, determined from an incremental peak V ̇2 test, with 1 min recovery between intervals (HIIR). On day 2, capillary blood samples were taken in the fasted state and at pre-determined intervals throughout the 6.5 h postprandial period while participants rested. A standardised breakfast was consumed at 08:00 immediately after the fasting sample and a standardised lunch meal at 12:00. RESULTS: Differences in fasting plasma [TAG] were small to moderate (95% confidence interval (95% CI) -0.11 to 0.01, Effect size (ES) = 0.40). Postprandial [TAG] was lower during HIIR compared with CON (95% CI -0.19 to -0.02, ES = 0.58). The total area under the [TAG] versus time curve was lower following HIIR compared with CON (5.2(1.1) vs. 5.8(1.5) mmol·L 6.5 h; 95% CI -1.18 to -0.12, ES = 0.50). CONCLUSIONS: This is the first study to show that low volume, high-intensity interval running attenuates postprandial [TAG] in healthy, active 11 to 12 year old boys

High-intensity running and energy restriction reduces 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-year-old girls (mean(SD): body mass 45.1(7.6) kg; peak oxygen uptake (V˙O2) 43(6) mL·kg·min) completed three, 2-day conditions in a counterbalanced, crossover design separated by 14 days. On day 1, participants completed 10×1 min interval runs (HIIR), 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 pre-determined intervals throughout the 6.5 h postprandial period. A standardised breakfast and lunch were consumed immediately and 4 h, respectively, after the fasting sample. 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). CONCLUSION: Manipulations of HIIR and ER reduce postprandial [TAG] in girls. The magnitude of effect was marginally, though not meaningfully, greater following HIIR than HIIR-ER

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 to 16 h before a standardised 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

Energy replacement diminishes the effect of exercise on postprandial lipemia in boys

Purpose: Acute bouts of exercise reduce postprandial triacylglycerol concentrations ([TAG]) in healthy boys and girls; however, it is not known whether this effect is mediated by the energy deficit. This study examined whether the exercise-induced reduction in postprandial [TAG] persists after immediate dietary replacement of the exercise energy expenditure (EE). Methods: Eighteen healthy 11- to 13-year-old boys (mean(SD): body mass 41.3(8.4) kg; peak oxygen uptake ( VO 2) 55(5) mL·kg-1·min-1) completed three, 2-day conditions in a within-measures, crossover design separated by 14 days. On day 1, participants rested (CON), exercised at 60% peak VO 2 inducing a net EE of 32 kJ·kg-1 body mass (EX-DEF) or completed the same exercise with the net EE replaced immediately (EX-REP). On day 2, capillary blood samples were taken in the fasted state and at pre-determined intervals throughout the 6.5 h postprandial period. A standardised breakfast and lunch meal were consumed immediately and 4 h, respectively, after the fasting sample. Results: Based on ratios of the geometric means (95% confidence intervals (CI) for ratios), EX-DEF fasting [TAG] was 19% and 15% lower than CON (-32 to -4%, ES = 1.15, P = 0.02) and EX-REP (-29 to 0%, ES = 0.91, P = 0.05) respectively; CON and EX-REP were similar (-4%; P = 0.59). The EX-DEF total area under the [TAG] versus time curve was 15% and 16% lower than CON (-27 to 0%, ES = 0.55, P = 0.05) and EX-REP (-29 to -2%, ES = 0.62, P = 0.03) respectively; CON and EX-REP were not different (2%; -13 to 20%, P = 0.80). Conclusion: Immediate replacement of the exercise-induced energy deficit negates the reduction in postprandial [TAG] in boys; this highlights the importance of maintaining a negative energy balance immediately post-exercise to maximise the metabolic health benefits of exercise

Sex differences in postprandial lipaemia after acute high-intensity interval running in young people

Acute exercise reduces postprandial triacylglycerol concentrations ([TAG]) in boys and girls; however, it is not known whether between-sex differences exist in response to exercise. Fifteen boys (mean(SD): 11.8(0.4) years) and sixteen girls (12.1(0.7) years) completed two, 2-day conditions. On day 1, participants rested (CON) or completed 10×1 min high-intensity interval runs at 100% maximal aerobic speed with 1 min recovery (HIIR). On day 2, participants consumed a standardised breakfast and lunch over a 6.5-h period during which seven capillary blood samples were collected. Based on ratios of the geometric means (95% CI for ratios), fasting [TAG] was 32% lower in boys than girls (-44 to -18%, ES=1.31, P<0.001), and 12% lower after HIIR than CON (-18 to -5%, ES=0.42, P=0.003); the magnitude of reduction was not significantly different between the sexes (8% (ES=0.36) vs. 15% (ES=0.47), respectively; P=0.29). The total area under the [TAG] versus time curve was 27% lower in boys than girls (-40 to -10%, ES=1.02, P=0.005), and 10% lower after HIIR than CON (-16 to -5%, ES=0.36, P=0.001); the magnitude of reduction was similar between the sexes (11% (ES=0.43) vs. 10% (ES=0.31), respectively; P=0.87). The small-moderate reduction in postprandial [TAG] after HIIR was similar between the sexes