Carbohydrate supplementation and prolonged intermittent, high-intensity exercise in adolescents: research findings, ethical issues and suggestions for the future

In the last decade, research has begun to investigate the efficacy of carbohydrate supplementation for improving aspects of physical capacity and skill performance during sport-specific exercise in adolescent team games players. This research remains in its infancy, and further study would be beneficial considering the large youth population actively involved in team games. Literature on the influence of carbohydrate supplementation on skill performance is scarce, limited to shooting accuracy in adolescent basketball players and conflicting in its findings. Between-study differences in the exercise protocol, volume of fluid and carbohydrate consumed, use of prior fatiguing exercise and timing of skill tests may contribute to the different findings. Conversely, initial data supports carbohydrate supplementation in solution and gel form for improving intermittent endurance running capacity following soccer-specific shuttle running. These studies produced reliable data, but were subject to limitations including lack of quantification of the metabolic response of participants, limited generalization of data due to narrow participant age and maturation ranges, use of males and females within the same sample and non-standardized pre-exercise nutritional status between participants. There is a lack of consensus regarding the influence of frequently consuming carbohydrate-containing products on tooth enamel erosion and the development of obesity or being overweight in adolescent athletes and non-athletes. These discrepancies mean that the initiation or exacerbation of health issues due to frequent consumption of carbohydrate-containing products by adolescents cannot be conclusively refuted. Coupled with the knowledge that consuming a natural, high-carbohydrate diet ∼3–8 hours before exercise can significantly alter substrate use and improve exercise performance in adults, a moral and ethical concern is raised regarding the direction of future research in order to further knowledge while safeguarding the health and well-being of young participants. It could be deemed unethical to continue study into carbohydrate supplementation while ignoring the potential health concerns and the possibility of generating similar performance enhancements using natural dietary interventions. Therefore, future work should investigate the influence of pre-exercise dietary intake on the prolonged intermittent, high-intensity exercise performance of adolescents. This would enable quantification of whether pre-exercise nutrition can modulate exercise performance and, if so, the optimum dietary composition to achieve this. Research could then combine this knowledge with ingestion of carbohydrate-containing products during exercise to facilitate ethical and healthy nutritional guidelines for enhancing the exercise performance of adolescents. This article addresses the available evidence regarding carbohydrate supplementation and prolonged intermittent, high-intensity exercise in adolescent team games players. It discusses the potential health concerns associated with the frequent use of carbohydrate-containing products by adolescents and how this affects the research ethics of the field, and considers directions for future work

Hydration status and fluid balance of elite European youth soccer players during consecutive training sessions

The objective of the study was to investigate the hydration status and fluid balance of elite European youth soccer players during three consecutive training sessions. Fourteen males (age 16.9 ± 0.8 years, height 1.79 ± 0.06 m, body mass (BM) 70.6 ± 5.0 kg) had their hydration status assessed from first morning urine samples (baseline) and pre- and post-training using urine specif-ic gravity (USG) measures, and their fluid balance calculated from pre- to post-training BM change, corrected for fluid intake and urine output. Most participants were hypohydrated upon waking (USG >1.020; 77% on days 1 and 3, and 62% on day 2). There was no significant difference between first morning and pre-training USG (p = 0.11) and no influence of training session (p = 0.34) or time (pre- vs. post-training; p = 0.16) on USG. Significant BM loss occurred in sessions 1-3 (0.69 ± 0.22, 0.42 ± 0.25, and 0.38 ± 0.30 kg respectively, p < 0.05). Mean fluid intake in sessions 1-3 was 425 ± 185, 355 ± 161, and 247 ± 157 ml, respectively (p < 0.05). Participants replaced on average 71.3 ± 64.1% (range 0-363.6%) of fluid losses across the three sessions. Body mass loss, fluid intake, and USG measures showed large inter-individual variation. Elite young European soccer players likely wake and present for training hypohydrat-ed, when a USG threshold of 1.020 is applied. When training in a cool environment with ad libitum access to fluid, replacing ~71% of sweat losses results in minimal hypohydration (<1% BM). Consumption of fluid ad libitum throughout training ap-pears to prevent excessive (≥2% BM) dehydration, as advised by current fluid intake guidelines. Current fluid intake guide-lines appear applicable for elite European youth soccer players training in a cool environment

The influence of serial carbohydrate mouth rinsing on power output during a cycle sprint

The objective of the study was to investigate the influence of serial administration of a carbohydrate (CHO) mouth rinse on performance, metabolic and perceptual responses during a cycle sprint. Twelve physically active males (mean (± SD) age: 23.1 (3.0) years, height: 1.83 (0.07) m, body mass (BM): 86.3 (13.5) kg) completed the following mouth rinse trials in a randomized, counterbalanced, double-blind fashion; 1. 8 x 5 second rinses with a 25 ml CHO (6% w/v maltodextrin) solution, 2. 8 x 5 second rinses with a 25 ml placebo (PLA) solution. Following mouth rinse administration, participants completed a 30 second sprint on a cycle ergometer against a 0.075 g·kg-1 BM resistance. Eight participants achieved a greater peak power output (PPO) in the CHO trial, resulting in a significantly greater PPO compared with PLA (13.51 ± 2.19 vs. 13.20 ± 2. 14 W·kg-1, p < 0.05). Magnitude inference analysis reported a likely benefit (81% likelihood) of the CHO mouth rinse on PPO. In the CHO trial, mean power output (MPO) showed a trend for being greater in the first 5 seconds of the sprint and lower for the remainder of the sprint compared with the PLA trial (p > 0.05). No significant between-trials difference was reported for fatigue index, perceived exertion, arousal and nausea levels, or blood lactate and glucose concentrations. Serial administration of a CHO mouth rinse may significantly improve PPO during a cycle sprint. This improvement appears confined to the first 5 seconds of the sprint, and may come at a greater relative cost for the remainder of the sprint

Carbohydrate gel ingestion significantly improves the intermittent endurance capacity, but not sprint performance, of adolescent team games players during a simulated team games protocol

The aim of this study was to investigate the influence of ingesting a carbohydrate (CHO) gel on the intermittent endurance capacity and sprint performance of adolescent team games players. Eleven participants [mean age 13.5 ± 0.7 years, height 1.72 ± 0.08 m, body mass (BM) 62.1 ± 9.4 kg] performed two trials separated by 3–7 days. In each trial, they completed four 15 min periods of part A of the Loughborough Intermittent Shuttle Test (LIST), followed by an intermittent run to exhaustion (part B). In the 5 min pre-exercise, participants consumed 0.818 mL kg−1 BM of a CHO or a non-CHO placebo gel, and a further 0.327 mL kg−1 BM every 15 min during part A of the LIST (38.0 ± 5.5 g CHO h−1 in the CHO trial). Intermittent endurance capacity was increased by 21.1% during part B when the CHO gel was ingested (4.6 ± 2.0 vs. 3.8 ± 2.4 min, P < 0.05, r = 0.67), with distance covered in part B significantly greater in the CHO trial (787 ± 319 vs. 669 ± 424 m, P < 0.05, r = 0.57). Gel ingestion did not significantly influence mean 15 m sprint time (P = 0.34), peak sprint time (P = 0.81), or heart rate (P = 0.66). Ingestion of a CHO gel significantly increases the intermittent endurance capacity of adolescent team games players during a simulated team games protocol

The effects of two weeks self-regulated high-intensity interval training on cardiorespiratory fitness, exercise enjoyment, and intentions to repeat

This study investigated the effect of low-volume self-regulated high-intensity interval training (SR-HIIT) on cardiorespiratory fitness (CRF), exercise enjoyment, and intentions to repeat. Ten untrained, physically active adults (five males and five females, age: 20.3 ± 0.5 years) undertook a 2-week control period followed by 2-weeks SR-HIIT (6 x 10 min cycle ergometer sessions). Sessions involved alternate bouts at a rating of perceived exertion of 17 (work) and 11 (recovery), with bout durations self-regulated by the participant. Maximal aerobic capacity showed a small increase from post-control (3.14 ± 1.03 L.min-1) to post-training (3.45 ± 1.14 L.min-1; ̅diff 0.31, 95%CI 0.06 L.min-1, d = 0.28, 95%CL 0.11, 0.45). First ventilatory threshold showed a large increase from post-control (65.6 ± 2.1% V̇O2max) to post-training (68.0 ± 2.4% V̇O2max; ̅diff 2.4, 95%CI 1.2%, d = 0.96, 95%CL 0.27, 1.62). Post-exercise enjoyment showed small (̅diff 3.5, 95%CI 8.1 AU, d = 0.31) and medium (̅diff 6.9, 95%CI 6.7 AU, d = 0.68) increases from SR-HIIT session 1-3 and 3-6, respectively. There were trivial to medium increases in intention to repeat SR-HIIT once per week (d = 0.06 to 0.63) and three times per week (d = 0.28 to 0.60). Low-volume SR-HIIT elicits meaningful improvements in CRF, is enjoyable, and facilitates good intentions to repeat, and may be an additional option for implementing HIIT to improve general population health and fitness

Incremental Scheduling Engines for Human Exploration of the Cosmos

As humankind embarks on longer space missions farther from home, the requirements and environments for scheduling the activities performed on these missions are changing. As we begin to prepare for these missions it is appropriate to evaluate the merits and applicability of the different types of scheduling engines. Scheduling engines temporally arrange tasks onto a timeline so that all constraints and objectives are met and resources are not overbooked. Scheduling engines used to schedule space missions fall into three general categories: batch, mixed-initiative, and incremental. This paper presents an assessment of the engine types, a discussion of the impact of human exploration of the moon and Mars on planning and scheduling, and the applicability of the different types of scheduling engines. This paper will pursue the hypothesis that incremental scheduling engines may have a place in the new environment; they have the potential to reduce cost, to improve the satisfaction of those who execute or benefit from a particular timeline (the customers), and to allow astronauts to plan their own tasks and those of their companion robots

Extremely short duration sprint interval training improves vascular health in older adults

Exercise improves health and physical function in older people, but very few older people participate although the trend is for increasing participation. This study sought to determine whether short duration sprint interval training (SIT) improves health and physical function in older people. Seventeen (9 M and 8 F) older adults (age 66 ± 3 years) were recruited. Participants had blood pressure, physical function and blood lipid profile measured and were then allocated to a control group (CON n = 7) or a SIT group (n = 10). The control group maintained daily activities; the SIT group performed 10 weeks of twice-weekly training sessions of 6-s sprints. By week 10, training sessions lasted 11.6 ± 0.6-min. Ten weeks of SIT resulted in significant changes in pulse pressure (CONpre 59 ± 18 mmHg; CONpost 60 ± 9 mmHg; SITpre 56 ± 14 mmHg; SITpost 49 ± 7 mmHg; p = 0.007), mean blood pressure (CONpre 100 ± 10 mmHg; CONpost 97 ± 11 mmHg; SITpre 102 ± 7 mmHg; SITpost 93 ± 8 mmHg; p = 0.003), timed get up and go (CONpre 6.9 ± 1.1 s; CONpost 6.9 ± 1.0 s; SITpre 7.4 ± 1.2 s; SITpost 6.6 ± 1.0 s; p = 0.005), loaded 50 m walk (CONpre 6.9 ± 1.1 s; CONpost 6.9 ± 1.0 s; SITpre 7.4 ± 1.2 s; SITpost 6.6 ± 1.0 s; p = 0.005),and total cholesterol: HDL cholesterol ratio (CONpre 4.2 ± 0.7; CONpost 4.0 ± 0.7; SITpre 4.4 ± 1.1; SITpost 3.2 ± 0.7; p = 0.01). SIT is an effective way to maintain blood pressure, lipid profile, and physical function during aging and is an effective tool for promoting optimal aging