Metabolism and exercise during youth

Metabolism and exercise during yout

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

Recommendations for recruiting and retaining adolescent girls in chronic exercise (training) research studies

This is an accepted manuscript of an article published by MDPI in Sports on 26/08/2015, available online: https://doi.org/10.3390/sports3030219 The accepted version of the publication may differ from the final published version.Extensive challenges are often encountered when recruiting participants to chronic exercise (training) studies. High participant burden during chronic exercise training programmes can result in low uptake to and/or poor compliance with the study. The aim of this qualitative study was to identify factors affecting adolescent girls’ recruitment and adherence to chronic exercise training research studies. Twenty-six adolescent girls (aged 12 to 15 years) participated in one of five focus groups discussing recruitment and retention to exercise physiology research involving a chronic exercise training programme. A thematic analysis was used to analyse the data and eight final themes were inductively identified. Seven evidence-based practical recommendations are suggested to improve the recruitment and retention of participants for prospective, chronic exercise training studies. Successful recruitment requires: (i) the defining of exercise-related terms; (ii) appropriate choice of recruitment material; and (iii) an understanding of participant motivations. Retention strategies include: (iv) regular monitoring of participant motives; and (v) small groups which foster peer and researcher support. Finally, (vi) friendship and ability groups were favoured in addition to (vii) a variety of activities to promote adherence to an exercise training programme

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

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

Effect of breakfast omission and consumption on energy intake and physical activity in adolescent girls: a randomised controlled trial

It is not known if breakfast consumption is an effective intervention for altering daily energy balance in adolescents when compared with breakfast omission. This study examined the acute effect of breakfast consumption and omission on free-living energy intake (EI) and physical activity (PA) in adolescent girls. Using an acute randomised crossover design, forty girls (age 13.3 ± 0.8 y, body mass index 21.5 ± 5.0 kg∙m-2) completed two, 3-day conditions in a randomised, counter-balanced order: no breakfast (NB) and standardised (~1962 kJ) breakfast (SB). Dietary intakes were assessed using food diaries combined with digital photographic records and PA was measured via accelerometry throughout each condition. Statistical analyses were completed using repeated measures analysis of variance. Post-breakfast EI was 483 ± 1309 kJ/d higher in NB vs. SB (P=0.025), but total daily EI was 1479 ± 1311 kJ/d higher in SB vs. NB (P<0.0005). Daily carbohydrate, fibre and protein intakes were higher in SB vs. NB (P<0.0005), whereas daily fat intake was not different (P=0.405). Effect sizes met the minimum important difference of ≥0.20 for all significant effects. Breakfast manipulation did not affect post-breakfast macronutrient intakes (P≥0.451) or time spent sedentary or in PA (P≥0.657). In this sample of adolescent girls, breakfast omission increased post-breakfast free-living EI, but total daily EI was greater when a standardised breakfast was consumed. We found no evidence that breakfast consumption induces compensatory changes in PA. Further experimental research is required to determine the effects of extended periods of breakfast manipulation in young people

Criterion Validity of a Field-Based Assessment of Aerobic Capacity in Wheelchair Rugby Athletes

Purpose: To confirm whether peak aerobic capacity determined during laboratory testing could be replicated during an on-court field-based test in wheelchair rugby (WR) players. Methods: Sixteen WR players performed an incremental speed-based peak oxygen uptake (V̇O2peak) test on a motorised treadmill (TM) and completed a Multi-stage Fitness Test (MFT) on a basketball court in a counter-balanced order while spirometric data were recorded. A paired t-test was performed to check for systematic error between tests. A Bland-Altman plot for V̇O2peak illustrated the agreement between the TM and MFT results and how this related to the boundaries of practical equivalence. Results: No significant differences between mean V̇O2peak were reported (TM:1.85±0.63 vs. MFT: 1.81±0.63 L.min-1; p=0.33). Bland-Altman plot for V̇O2peak suggests that the mean values are in good agreement at the group level; i.e., the exact 95% confidence limits for the ratio systematic error (0.95 to 1.02) are within the boundaries of practical equivalence (0.88 to 1.13) showing the group average TM and MFT values are interchangeable. However, consideration of the data at the level of the individual athlete suggests the TM and MFT results were not interchangeable because the 95% ratio limits of agreement either coincide with the boundaries of practical equivalence (upper limit) or fall outside (lower limit). Conclusions: Results suggest that the MFT provides a suitable test at a group level with this cohort of WR players for the assessment of V̇O2peak (range 0.97 – 3.64 L∙min-1), yet caution is noted for interchangeable use of values between tests for individual players

A multi-factorial assessment of elite paratriathletes’ response to two weeks of intensified training

Purpose: In able-bodied athletes, several hormonal, immunological and psychological parameters are commonly assessed in response to intensified training due to their potential relationship to acute fatigue and training/non-training stress. This has yet to be studied in Paralympic athletes. Methods: Ten elite paratriathletes were studied for five weeks around a 14-day overseas training camp whereby training load was 137% of pre-camp levels. Athletes provided: six saliva samples (one pre-camp, four during camp, one post-camp) for cortisol, testosterone and secretory immunoglobulin A; weekly psychological questionnaires (POMS and RESTQ-S); daily resting heart rate and subjective wellness measures including sleep quality and quantity. Results: There was no significant change in salivary cortisol, testosterone, cortisol:testosterone ratio or secretory immunoglobulin A during intensified training (p≥0.090). Likewise, there was no meaningful change in resting heart rate or subjective wellness measures (p≥0.079). Subjective sleep quality and quantity increased during intensified training (p≤0.003). There was no significant effect on any POMS subscale other than lower anger (p=0.049) whilst there was greater general recovery and lower sport and general stress from RESTQ-S (p≤0.015). Conclusions: There was little to no change in parameters commonly associated with the fatigued state which may relate to the training camp setting minimising external life stresses and the careful management of training loads from coaches. This is the first evidence of such responses in Paralympic athletes

High thermoregulatory strain during competitive paratriathlon racing in the heat

Purpose: Paratriathletes may display impairments in autonomic (sudomotor and/or vasomotor function) or behavioural (drinking and/or pacing of effort) thermoregulation. As such, this study aimed to describe the thermoregulatory profile of athletes competing in the heat. Methods: Core temperature (Tc) was recorded at 30 s intervals in 28 mixed-impairment paratriathletes during competition in a hot environment (33oC, 35-41% relative humidity, 25-27oC water temperature), via an ingestible temperature sensor (BodyCap e-Celsius). Furthermore, in a subset of 9 athletes, skin temperature (Tsk) was measured. Athletes’ wetsuit use was noted whilst heat illness symptoms were self-reported post-race. Results: Twenty-two athletes displayed a Tc ≥39.5oC with 8 athletes ≥40.0oC. There were increases across the average Tc for swim, bike and run sections (p≤0.016). There was no change in Tsk during the race (p≥0.086). Visually impaired athletes displayed a significantly greater Tc during the run section than athletes in a wheelchair (p≤0.021). Athletes wearing a wetsuit (57% athletes) had a greater Tc when swimming (p≤0.032) whilst those reporting heat illness symptoms (57% athletes) displayed a greater Tc at various timepoints (p≤0.046). Conclusions: Paratriathletes face significant thermal strain during competition in the heat, as evidenced by high Tc, relative to previous research in able-bodied athletes, and a high incidence of self-reported heat illness symptomatology. Differences in the Tc profile exist depending on athletes’ race category and wetsuit use

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